Construction Technology 2 Lecture Notes PDF

lOMoARcPSD|48705191 Construction Technology 2 Lecture Notes Construction Technology 2 (University of Technology Sydney) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by isabella ricchiu...

lOMoARcPSD|48705191 Construction Technology 2 Lecture Notes Construction Technology 2 (University of Technology Sydney) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 NCC Mandatory minimum standard which does not guarantee a building will be fit for purpose Sets standard for safety, health, amenity, accessibility and sustainability Allows for flexibility in how performance requirements are achieved and allows different compliance solutions (DTS and or performance solutions) For multi use buildings each part must be classified separately unless it is less than 10% of floor area Reference documents can be used as DTS options and provide prescriptive detail Sole Occupancy Unit - a room or other part of a building for occupation by one or joint owners, lessees, tennants or other occupiers to the exclusion of others Townhouses Joined in a continuous row with common noise/fire wall between SOU Often under strata title due to shared garages etc Apartments More complicated fire egress due to shared stairs Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 WEEK 2 Reinforced Concrete Formwork is strong and secure Number and configuration of reinforcement bars and mesh are correct Cover level is correct Correct concrete strength Vibration and surface finish are correct Curing is carried out properly to spec and formwork is not stripped early Before Starting Understanding of drawings/specs/scope of works Existing site conditions e.g geotechnical report Review environmental report Shoring design Development consent and traffic management Material types - soil, clay, sandstone or shale Noise and vibration requirements Access requirements Prepare BoQ Prepare a program Ensure service locations are found Selection of specialist subcontractor Selection of plant required Excavator Cut, scoop, carry and tip Dozer Pushing soil or ripping soil or rock Drot Multi use front bucket Can cut, push, load, scrape, tip, clamshell Dewatering Water table is the level where sub-ground soil becomes saturated with groundwater Dewatering is needed to stabilize soil and prevent collapse and can be achieved with well points and wells Well points are usually a borehole with a liner and pump Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Material Classification Virgin excavated material (VENM) Excavated natural material (ENM) General solid waste (GSW) Asbestos impacted GSW Restricted solid waste (RSW) Industrial Waste Hazardous Waste Acid Sulphate Soil (ASS) Putrescible waste Shoring Supporting or retaining a structure or soil to prevent collapse Piling Supports footings of building structures Reinforced piles with Shotcrete Infill WEEK 3 Concrete Blocks Can be reinforced with mild steel reo bars Strong permanent formwork for reinforced concrete 200mm is quick and easy to place No crane required to place Can be damp without damage Waterproofing is easy Dimensionally stable Reasonably economical Alternatives to Concrete Blocks Contiguous or Non-Contiguous Piles Leave In Place Formwork Quick Quick Needs special equipment No special equipment Small pool of contractors Large pool of contractors Good solution if basement is on Does not work if basement on boundary boundary Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Concrete Masonry Concrete ○ Durable ○ Doesn’t grow but slightly shrinks ○ Small dimensional variation ○ Appearance Masonry ○ Flexible small units ○ Ease of construction Blocks ○ Structural advantage - flexural strength of reinforced blocks ○ Unreinforced masonry is not that strong - especially under horizontal load Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Block Sizes 100 series - 90mm block + 10mm joint 150 series - 140mm block + 10mm joint 200 series - 190mm +10mm 300 series - 290mm + 10mm 200 Hollow is the most commonly used 190mm + 10mm mortar joint = 200 module 390mm long + 10mm mortar joint = 400 module Coding Format for Reinforcing Steel N - nominal ductility - 500MPa for deformed bar and 250MPa for round bar Deformed Bar - have raised ribs to improve mechanical grip between steel and concrete to improve shear performance Round Bars - smooth and used for fitment and ligatures that hold main bars in a cage assembly N16-400 ○ N is the diameter of the bar ○ 400 is the spacing between bars which can be vertical or horizontal Splice - amount of overlap when tying bars Cogs and Hooks - bends in the bar that anchor the bar into concrete and cage set out AS3600-2018 - deemed to satisfy NCC Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Concrete masonry is being made up to 30% lighter e.g 20.01 blocks weigh 11kg with 15MPa Replacing stone aggregate with bottom ash from coal fired furnaces or slag sad from steel production Half the cement is replaced with slagment Concrete shrinks so ensure is the properly cured to AS3700 Mortar Joint Provide even bedding for bricks Transmit compressive load Hold or bond unit to carry tensile or shear forces Use clean washed sand Grouting Cores Grout can be poured by hand into hoppers or pumped Cores must be clean and free of mortar - clean out openings are usually provided for at the bottom but sealed with formwork during grout Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 pour In hot weather may need to hose out 30 mins before to cool blocks and prevent ash setting Grouting of over 3m should not be done in one pour Minimum 12MPa preferably 20MPa Minimum cement content of 300kg/m3 Aggregate of course gravel 10mm size Control Joints Prevent cracking caused by movement ○ Shrinkage of masonry or expansion of clay masonry ○ Temperature movement ○ Differential settlement of footings - hogging (top) or sagging (bottom) Provided at major changes in wall height, wall thickness, CJ in door or roof slab, T junctions or in straight walls with special CJ blocks (20.09 or 20.10) Gravity Wall System Free draining Ease of construction Design flexibility Cost effective and compatible with most soil Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 WEEK 4 - Fire and Soundproofing The objective is to solve both issues economically and efficiently in one solution Often complex to meet NCC requirements Noise resistance failures cause more irritation than fire isolation due to fires not being common Fires should not spread beyond the room of ignition - or be kept in the single occupancy unit If it spreads between SOUs on one floor it should not spread to other floors If it does spread between floors occupants need time to escape and the structural integrity should not be compromised In the city, fire crews should arrive in less than 10 minutes NCC Safety Priority Life safety Stop spread of fire to other buildings or SOU Stop building collapse where collapse would be hazardous to occupants, emergency services or adjoining property Choosing a Fire/Noise Resistant Construction System (NCC) 1. Define NCC building classification/compliance pathway 2. Focus on noise performance requirement 3. Focus on fire performance requirement 4. Merge requirements and select compliant solution Step 1 Determine NCC class Determine basis for compliance - focus on DTS for floor, wall, ceiling Determine arrangement of SOU Each SOU is a compartment that defines which walls/floors are noise/fire resistant ○ Depends if SOU’s are side by side, stacked on top or adjoin different space ○ Walls and floors within SOU’s may need to be fire rated where they support fire rated wall or floor above Step 2 NCC Noise Requirements ○ Floors must provide insulation against transmission of airborne and impact generated noise ○ Walls must provide insulation against the transmission of airborne noise and impact generated if it is separating a bathroom, laundry, kitchen from a habitable room in another SOU ○ Noise insulation must not be compromised by service penetration or doors Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Understand noise types and how each is measured Determine noise insulation requirement and select system that meets or exceeds this Strategies to achieve noise resistance ○ Adding mass such as concrete ○ Isolate one side of wall from the other such as a double stud cavity wall ○ Avoid rigid connection between opposing side of floor floating doors, carpet, noise resilient channels ○ Use absorptive material to fill wall such as mineral wool ○ Sealing noise leaks around services, doors and windows Mass, air sealing and clever design can improve acoustic performance Windows and doors are usually weak spots Use thick or double glazing Acoustic seal between wall opening and window/door unit Gaskets around openable doors and windows Use of solid core doors Step 3 Safeguard people when fire occurs Evacuation Protect from structural failure Avoid fire spread between building DTS Solutions ○ Fire resistance and stability ○ Compartmentalization and stability ○ Protection of openings Determine type of construction for fire resistance Determine resistance level of elements Address special fire issues Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Types of Construction Type A ○ Highest level of passive protection ○ Structural elements to withstand burnout of building contents Type B ○ Lower level of passive construction ○ Less of the structure to withstand burnout of content Type C ○ Lowest level of passive protection ○ Only some elements need to have specified fire resistance to restrict fire spread ○ Often applies to class 1 and 2 Determining Fire Resistance Levels for Building Elements Minimum amount of time in minutes that building elements resist fire ○ Structural adequacy - ability to withstand load ○ Integrity - contain smoke, flame and gas ○ Insulation - limit temperature on the side away from fire ○ Expressed as 60/60/60 or --/60/-- Fire Engineering Take advantage of BCA provision which permit deemed to comply regulation to be sidestepped if fire safety objectives are met Fire engineer relies on software to predict flows of gases and smoke Smoke and gas management important, with sprinklers, smoke screens, smoke doors and exhaust systems used to replace compartmentalisation Keep egress routes clear Stop egress routes collapsing Isolation of compartment within low rise building Isolation of floor within high rise or at a wall built to boundary WEEK 5 - Basement Construction Basement construction is common in multi unit residential buildings for parking Often involves concrete block walls and poured in-situ concrete columns, built off strip and pad footings The suspended slab above (GF slab) serves a structural purpose by acting as a diaphragm to resist horizontal forces on basement walls caused by ground and hydrostatic pressure Blockwork Detail - Pile 4 on Reference Project Reinforce, core filled concrete block Strip fitting supports wall (3N12 with R10 ties) Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Load path from wal to strip footing Isolation joint separating infill slab from main structure Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Isolation Joint Relevant to infill Used to separate the concrete slab from abutting structures to prevent unwanted restraint Allows vertical and horizontal movement Joint will open and close with time and temperature changes Compressible, cellular materials are commonly used in the joint Basement Walls - Structural Strength and Waterproofing Significant attention must be paid to structural integrity and waterproofing Hydrostatic pressure from groundwater places load on retaining wall structure Creates pressure that forces water to infiltrate gaps in the walls causing leakage Similar to an in ground pool, but with water on the outside Not illegal or required to be waterproof, but is bad practice Wet Wall Construction Ground is up against the wall meaning it must keep moisture that is pressing against the wall Separate retaining wall outside the building, similar to a bored pier and shotcrete wall, which takes hydrostatic load and therefore soil and water is not pressing against wall Required attention for waterproofing and sub soil drainage Aim to drain/shed ground water to reduce hydrostatic pressure and load, which either drains into stormwater system or flows around A build on a slope will act as a dam to water on the upstream (high) side of building Civil or hydraulic engineers will assist architect to drainage requirement Fundamentals of Wet Wall Structural adequacy ○ Hydrostatic pressure ○ Earth Pressure ○ Superimposed pressure (above) Relieve hydrostatic pressure Provision of continuous and impervious waterproofing membrane or a method of draining water Approach to Selecting Wet Wall Retaining Systems Cost vs Performance and Durability - no requirement for durability in NCC Different standards of waterproofing depend on: ○ NCC Performance Requirements ○ Expected water quantity ○ Where is water table and weather variables ○ Habitable basement - must be waterproof ○ Non habitable - look at NCC or common sense Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Site Factors to Consider Expected run off of rain water and ability to drain Drainage capacity of soil (sand vs clay) Height of water table vs depth of basement - water pressure increases with depth Habitable vs Non-Habitable Spaces ○ 1 is highest, 4 is lowest 1. Habitable basements below water table and close to waterways - high hydrostatic load and wall is always immersed 2. Habitable spaces with minor hydrostatic loads - sites with good run-off/surface drainage 3. Non-habitable spaces with minor hydrostatic load - car parks 4. Non-building structure (landscaping) and minor hydrostatic load Reference project would be risk level 3 Methods can include: ○ Paint waterproof membrane using acrylic, polyurethane or bituminous paint ○ Apply it to outside of wall as hydrostatic pressure pushes membrane against wall ○ Drape plastic sheet over wall face ○ Create drainage zone in front of membrane to minimize hydrostatic pressure - an AG drain at base of wall, backfilled with gravel above ○ Moisture should not cause accelerated deterioration of components such as reinforcing steel Paint on Liquid Membrane Low risk basement Balconies Planter boxes and retaining wall Water tanks Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Self Adhesive Sheet Membrane Allows installation without heating membrane Uniform thickness eliminates problems Mid to high performance basement Retaining walls and ramps Torch On Membrane System Heat welding seams together High performance basement Tanking Lift pits and car parks Roofing Landscaped area and green roof Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Drawings Survey Architectural Structural Civil Mechanical Electrical Hydraulic Landscape BoQ List of items of components with quantities and rates Preparation is called “take off” - taking off quantities from drawing Can be done by QS or estimator Some BIM can include quantities, or use Buildsoft WEEK 6 - Long Slab Floor In Situ Reinforced Slab Good in terms of: ○ Noise and fire insulation ○ Thermal performance where acting as heat sink ○ Good strength and span ability ○ Termite resistance ○ Readily available and cost effective ○ Most common floor solution in apartments Downside ○ Labour intensive, especially with formwork - time consuming and expensive ○ Slow compared to prefabricated options ○ Back propping means service and cladding install delayed Reference Project uses ○ Reinforced blockwork basement wall ○ Reinforced concrete column ○ Masonry to floor level above basement Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 How Slabs Carry Load Span in one direction between opposing walls Main reinforcement placed at bottom of slab to deal with tension force Top steel is mainly for temperature/shrinkage control For a span between two opposing walls - weakness in tension in the bottom third of slab thickness so reinforcing steel in this area Slabs between many support points (continuous span) - at the line of support, reverse bending movement occurs which means top third goes into tension - and additional steel required to assist Slabs may protrude past support wall (overhanging balcony) and is called cantilever Support for the overhang comes from slab back span and whatever holds this down Load applied on top of the cantilever causes it to bend downwards, leads to top zone of the cantilever going into tension and needs tension reinforcing Slabs supported by columns are prone to punching shear forces - column punches through slab - therefore extra reinforcing required at the head of the column Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Reinforcing at Reentrant Corners For relatively thin flat plate slabs such as basement infill slab in reference project, extra reo bars are placed at internal ( re entrant) corners to prevent tearing and shear cracking at these locations Joints in Suspended Slabs Allow expansion (expansion joints) Control cracking of concrete (control or contraction joint) Construction joints on larger slabs for a break in the pour process Joints are rarely needed on small to medium projects Do not put joints under planets or where water will pond above them Care in locating them is important for aesthetic, practical process and end function Joints should be shown in drawings Occur in slabs, columns, stairs In vertical elements usually at the underside and/or topside of the slab or beam Where joints are visible there should be a rebate or similar to ensure it looks neat Dowelled Expansion/Contraction/Construction Joints Allow one direction movement in joint while retaining structural strength in transverse direction Used where large floor areas are broken into multiple pours ○ Create practical achievable work packages ○ Manage movement in the concrete ○ Allow elements such as ramps and stairs to connect to floor slabs while allowing some independent movement ○ Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Compressible board is used to form boundary/junction between 1st and 2nd poured slab section One end of the steel reo is bonded into the first slab (have deformed lugs to mechanically bond to concrete) Other end of dowel is embedded into 2nd pour but not bonded to concrete and often has a sleeve placed over it This allows for independent horizontal movement between slabs while also allowing load transfer Types of Suspended Slab Insitu - temporary formwork acts as a mould to support and shape wet concrete until it cures Precast - concrete components made off site and then joined Composite - hybrid of precast and insitu - usually beams are precast and matched with formwork that becomes part of the construction Economy of a floor system depends on: Minimising onsite labour Minimise construction period (floor to floor construction time) reducing amount of back propping, stripping time and providing early access for trades Cost of formwork can be more than 50% of floor cost Requirements of the specification Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Circumstances of floor system economics: Site access, crane usage Time - lead time, construction period Complexity of slab and beam layout Types of beams Extent of changes in floor level Availability of plant and equipment Formwork Popularity of insitu slab creates need for formwork Concrete cast on formwork consisting of plywood form sheets over bearers and joists Bearers held up with adjustable telescopic steel props which are freestanding or braced with metal frame Formwork is constructed to facilitate easy stripping and re-use - plywood is a waste of wood Need to keep overall floor cycle period short ○ Early stripping allows for early access for trades ○ Allows greater re use of formwork ○ Moving formwork from one floor to the next Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Traditional Formwork Used where labour cost is lower Most flexible formwork and suited to complicated layout Engineered Formwork System - Table Forms Usually built with prefabricated modules and a metal frame with plywood surface Advantages include speed, simplicity, safety and lower life cycle cost Loads on Formwork Dead loads - concrete, formwork Construction loads - workers, equipment, impacts Lateral loads - placement, spread, compaction Other lateral load on forms and shores - wind, inclined supports, transport equipment Formwork Operational Issues Joints are tight to prevent leaks Formwork clean of debris and water Ensure vibrator access Ensure conduits and embedded fitments in place Chamfer strips in place on exposed column and slab edge Grade of formwork - 1 is high quality 5 is areas that wont be seen Concrete Placement Inability to get good compaction and air pockets due to congested reinforcing steel and large aggregate size Excessive vibration will cause aggregate to separate Consider use of superplasticizers to allow free concrete flow Curing is vital for strength and reduce cracking and shrinkage Stripping Formwork Early strip allows construction to proceed faster and allows re use of form on active floor Stripping is left until concrete is able to take load - depends on slab span and temperature as advised by engineer Typical minimum strip time ○ Vertical surfaces - 2 days ○ Bottom forms of slab/beam less than 1800mm span - 7 days ○ Bottom forms of slab/beam greater than 1800mm span - 14 days ○ Pre or post stressing will reduce times Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Back Propping Propping until slab can support itself Enables reuse of formwork on subsequent floor Props in partial or full grid to distribute load to stronger slabs below Common for up to 3 floor to be partially or fully back propped Slows construction as other work cant proceed WEEK 7 - Brick, Brickwork and Cavity Walls Cavity masonry has been most common - with two leaves of masonry or brick veneer Cavity brick wall is not suitable for high exposure situation Cavity walls only one storey high with no eaves or protection will fail under bad exposure Failure is common when weather exposure is high, detailing is poor, construction is poor and brick or mortar is porous What are bricks made of? Clay bricks - fired in kiln to reduce moisture. Bricks must be used with expansion joints with longer walls typically called cracking Concrete bricks - made in a mould, steam cured and vibrated - often shrinks if larger bricks = slower shrinkage Calcium Silicate - low cost, low strength, high porosity and not often used Mixing clay and concrete in one wall should be avoided as shrinkage and expansion will occur Sustainability Implications of Bricks Bricks can be fired in electric kiln - which if using green energy can reduce carbon output Concrete bricks use cement which is highly energy intensive Clay and concrete bricks often have high embodied energy - but can be reused or recycled Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Damp Proof Course Stops rising damp from the ground as opposed to falling damp from the rain Most DPC and flashings used in cheap housing are now made of polyethylene Alcor - which is a bitumen coated aluminium sheet, is tougher than plastic but about twice as expensive DPC and flashings can also be made from lead, zinc and copper Key Success Criteria for Cavity Walls Only use a conventional cavity wall where exposure to driving rain is limited - if wind driven rain is anticipated, say a three storey building on a ridge, ensure top of cavity is ventilated to allow weep holes to drain Consider other materials, engineered facades being common where exposure is severe - any building over 3 storeys is unsuitable A cavity should only be 1 storey high - higher than that and the quantity of water on the inside face of the outer skin is likely to cause failure Specify bricks that are appropriate to the exposure - the lower the absorption the less likely the wall is to fail Ensure flashings are placed correctly, of good quality and have no holes - laps should be at least 150mm and bonded with appropriate material Ensure cavity is clean after construction and the weep holes drain effectively No electrical conduits or pipes in cavity Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Flashings become more critical as exposure of wall increases - higher buildings or on a ridge etc Flashings are fragile - careless work can cause failure of flashing and once covered are difficult to inspect No weep holes usually means no flashing A short flashing say for a ventilator may be allowed to drain into the cavity from the end The less water in the cavity - lower chance of failure Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 NCC Performance Requirements Structural performance Acoustic Performance Fire Performance DTS in the NCC AS1170 Loading Code defines loads AS3700 Masonry Structures describes and details brick construction Following codes will not make wall waterproof and will not make it durable or acceptance in appearance External Walls Two skins of brickwork, air cavity in between and wall tiles Outer skin is non load bearing in terms of vertical load - provide weather resistance, aesthetic (if face brick) and durability Inner skin is load bearing - often common brick and rendered for paint finish Mortar - adhesive to hold bricks together Wall ties run between skins to hold skins together and transfer lateral load Air cavity resists water transfer from outer to inner skin and provides insulation Weep holes - allow water from flashing to escape outwards Lintels - beams that carry load over openings Cement Render - adds a consistent layer (13 to 25mm) over brickwork for paint finish to add fire and sound resistance Internal Walls A single skin of brickwork with render or plasterboard lining - usually with furring channels May be load bearing or non-load bearing depending on structural design Brick Properties Durability ○ Exposure for severe marine environment ○ GP for other areas and internally Initial rate of absorption ○ How quickly water gets absorbed from mortar ○ Adjust the mortar to suit brick Can expand up to 2mm per metre - “E” factor for each brick type is provided Most expansion occurs within 2 weeks of firing - so leave if possible for 2 weeks to grow and therefore reduce problems Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Mortar Cement should be GP or GB - which has fly ash added Sand should be free of organic matter and have low clay content - no beach sand Water should be clean and fresh - potable Additives should only be used with manufacturers specification - no bycol or detergent Lime makes better mortar - more buttery and a bit weaker so mortar cracks and not bricks Mortar Grading and Batching Use correct grade for situation Classified by ratio of cement : lime : sand ○ M4 (Strongest) C1: L.05 : S 4.5 ○ M3 (Most common for external and internal load bearing wall) C1 : L1 : S6 ○ M2 (Internal non load bearing wall) C1 : L1 : S9 ○ M1 (Restoration work) C0 : L1 : S3 Wall Ties Transfer lateral load from outside wall to supporting structure Act under both tension and compression Designed to prevent water transfer across cavity - drip groove or drip line 3 classes - light, medium, heavy 5 Durability Classes R1-R5 (R5 most durable) - 316 grade stainless steel Normally placed at 600mm centres But at the top, sides and openings placed at 300mm centres Should be 50mm embedded in mortar DPC Prevent water rising up wall Stop dissolved salt attack rising up wall May be combined with flashing Must be installed up to a max of 150mm above grade Must protrude slightly from wall to prevent moisture passing around it Flashing Prevents water penetration around windows, doors, abutting roofs and chimneys Drains water from cavity to outer wall Complies with AS2904 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Expansion/Control Joints Bricks grow Bricks also expand and contract from climate change Both types of movement can cause problems in long or tall walls Joints are placed to prevent or control cracking and structural disharmony Can occur at windows and doors Slip Joints Typically used where brick walls support concrete slabs Provides vertical support but allows horizontal movement between dissimilar elements Basic approach is 2 sheets of thin metal with graphite dust or grease to enable slip Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Materials on Site Do not use broken or misshaped bricks Bond and Gauge Length and height of brick wall should be designed to maintain pattern and minimise brick cutting Bond refers to the overlap pattern in brickwork - overlapping makes it stronger than a grid pattern Wall height is governed by brick gauge - the incremental increase in height created by adding new course of brickwork to wall Most common is a stretcher bond wall Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Scaffolding Used to ensure bricklayer works comfortably Time consuming and adds cost - should use sparingly Articulation to deal with foundation and footing movement Breaks wall into separate panels - allows to move independently focusing the movement at the joints which often occur on the side of window or doors or behind downpipes WEEK 8 - Mass Timber Wood is only as good as the glue Casein glue is made from a milk byproduct Epoxy glue available since 1967 Subject to moisture and thermal movement and biological attack Popular food for white ants Objectives of using Timber Increased prefabrication offers the prospect of improved construction cost and delivery certainty Reduced site resources such as labour Improved site safety Renewable resource and low embodied energy in converting raw wood to usable construction components What is CLT Large and solid panels of timber made from wide planks, glued together in transverse layers Screed of either gypsum or polymer modified concrete used over CLT floor to improve acoustic and fire performance Pros Reduced construction duration High potential for off site manufacture Improved install speed and follow on trades Lightweight structures Deconstructable Cons Limited australian manufacturers Crane dependent Softwood only Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Can’t be exposed to exterior - needs cladding Need treatment for high hazard area WEEK 9 - Roof and Balcony Waterproofing NCC - Must prevent the penetration of water which may cause unhealthy or dangerous conditions or the loss of amenity for occupants, undue dampness or deterioration of building elements Waterproofing is a high risk item - poor workmanship, small leak holes, expensive to rectify and hard to find problems Balconies and flat roofs ○ Very small slope to facilitate drainage to outlets (1:60) ○ Two way fall commonly required ○ Water drainage points direct water to stormwater ○ Downpipes often concealed in ducts or externally mounted Parapet walls (for roofs) or hobs (for balconies) occur around the perimeter, therefore a flat roof, deck or balcony is akin to shallow swimming pool Penetrations through waterproofing from plumbing, air con and balustrading represent risks Fitness for Purpose Requirements Must be compatible with other materials in contact Withstand UV exposure Accommodate differential movement Withstand environmental conditions Last expected service life of overlaying finish or if no finish consider maintenance Membrane should be applied to the substrate not the tiling screen Substrate and surface of membrane should have falls to drainage outlet or free edge Water should not pond on membrane Will include other bonded or loose laid membrane, separation layer with structure or sound reduction layer Protected from UV, mechanical damage or anticipated movement from overlay Drained Cavity with Sheet Membrane Flat surface to terrace or deck No visible drains Fall can be higher without impacting usability No step at doors Membrane is serviceable Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Falls Falls prevent ponding and direct it to an outfall or drain Overall height of the fall affects external floor levels relative to internal floor levels Substrates Insitu concrete is most common and easiest to achieve 2 way falls - tooled in Precast requires a topping slab to achieve falls Timber is often common floor in townhouses - not in wet areas ○ Easy for 1 way fall, harder for 2 way fall Must consider differences in finished floor heights between interior and exterior Must consider movement required between substance and membrane Issues for achieving falls Tile size - large tiles make it harder to achieve 2 way falls especially near drains - mosaic tiles good on floor, large tiles for walls Required tile screen/bed thickness may be influenced by internal to external floor height and inclusion of reinforcement Exposure Exposed ○ Higher than 3 storeys or 9m above ground ○ Exposed to extreme weather ○ Facing flat terrain or water Sheltered ○ Less than 9m or shielded from direct wind ○ Contains shelter structures from rain and wind Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Shrouds should be fitted over weep holes to deflect high wind pressure Cross cavity flashing should extend up the cavity further than usual Efflorescence An accumulation of calcium crystal or soluble salt that disfigures outer surface of concrete and tiled balcony Saturation of mortar tile bed allows free lime to dissolve and migrate to surface causing stains Minimised by providing positive fall into the substrate before any membrane and overlay screed is applied Stop water entering tile bed by grouting and applying membrane again or water resistant tile bed Membrane Protection Protection needed to prevent mechanical damage to the waterproofing system Permanent protection can be built into the system such as drainage cells, heavy building plastic or tiles Permanent protection that can be built into the system can also function as thermal or sound attenuation such as rubber or cork mat Membrane Types Fully Bonded to Substrate ○ Liquid membranes that stick to substrate ○ Sheet membrane which require primer, then peel and stick ○ Sheet membrane which require primer, then heat melting to bond to substrate Partially Bonded/Mechanically Fixed ○ Sheet membrane with welded laps, terminations or penetrations ○ Can remain unattached to horizontal substrate but fixed at vertical surface ○ Fixed with mechanical fastening or spot bonded bitumen Unbonded ○ Similar to above but is typically held down with ballast to resist uplift Failure in Membrane Movement at joints Differential movement between dissimilar materials Deflection on floor during or after install Shrinkage Temperature and moisture variation Membrane Classification Class 1 - Low extensibility - usually liquid membrane Class 2 - Medium extensibility - Class 3 - High extensibility Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Membrane Flexibility Fabric reinforcement will alter membrane characteristics More rigid = more attention at wall/floor junctions and joint Choice of bond breaker at wall/floor junctions is vital Terminating the membrane At hobs, upturns or downturns or other terminations ○ Seal or cap the leading edge of membrane ○ Protect ingress of moisture behind membrane ○ Support membrane ○ Direct moisture flows Capping at Termination Points Usually preformed metal flashing that overlaps membrane Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Termination at Penetrations Surface Layer/Finishes Concrete topping screed Tiles or stone made on sand cement screed Pavers on stabilized sand Pavers on support pads Timber decking on battens Pedestal System - water drains between tile gaps Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Balustrading Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Alternatives to Waterproofing Chemical additives to concrete mix which helps concrete become waterproof WEEK 10 - Stairs and Wall Finishes Square Meters Sq m Usable Floor Area (UFA) Sq m Net Lettable Floor Area (NLA) Sqm Gross Floor Area (GFA) - source of costing information for a QS is 1.2 to 2 times the usable floor area - as allows for services etc Typical stair between 2 floors is approx 3.1m floor to floor Risers 3100 / 172 = 18 risers - possible under NCC One flight with 17 goings - landing not counted Goings - 17 x 280 = 4.8m Width by length - 1m x 4.8 = 5sq m Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Stair Ergonomics Slope - 2R + G = 540 - 700 (2 risers and 1 going) Regularity of risers and going Non slip surfaces Landings to stop falls Dog leg safer than continuous Stair Materials Reinforced or prestressed concrete Steel no less than 6mm thick Timber no less than 44mm and not joined with glue NCC Not more than 18 and not less than 2 risers in any flight Cannot fit 125mm sphere between risers or balustrade Issues for Stairs and Fire Egress Fire doors onto stairways must suit FRL’s and be self closing Must be enough exits to escape from a dwelling to open space Stairs must be wide enough to let building population escape efficiently Stair Design Minimum balustrade height - 1000mm min for flat and 865mm from nosing of stair tread Minimum baluster spacing (125mm sphere) Minimum landing areas (750mm from door to stair) Going - horizontal dimension from the front to the back of a tread less any overhang from the next tread above Landing - area at the top or bottom or between 2 flights Riser - height between consecutive tread Tapered tread - a stair tread with a walking area that grows smaller towards 1 end Concrete usually has the best fire rating for fire egress routes, is stronger and more durable as well as being less noisy than timber Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Render Finishes Typically applied over masonry/concrete Provides: ○ Smooth, flat surface over a rough surface ○ Improves water resistance but is not waterproof ○ Decorative finish ○ Can improve sound rating if meets thickness requirement ○ Requires good QC ○ Labour intensive and large scaffold ○ If not done well is prone to cracking Basic Requirements Render mix must be suitable for substrate Materials Cement Lime - minimises cracking Sand - coarse for undercoats and finer for finishing coats Water Admixtures such as plasticizers Substrate Prep Remove loose materials, dirt and grease Provide keyed surface as required Dampen wall to avoid sucking moisture from wall Number of Coats Usually 1 or 2 depending on: ○ Alignment/unevenness of substrate ○ Weather conditions exposed to ○ Type of finish ○ Allow 3 days to dry between coats Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Types of Coat Dash ○ Flicked or splattered onto background to product rough finish Undercoat/Scratch Coat ○ Thickness of 10mm-15mm ○ Semi dry surface is raked or scratched to provide a key for next coat Final Coat ○ Cement render applied by trowel over undercoat Set Coat ○ Not often used ○ 3mm hard plaster trowel on finish ○ Can be applied as final coat over cement render or direct to underside of concrete slab ○ Generally provides higher quality Alternative Materials Acrylic render more common - thinner coat thickness, greater flexibility and used on flat surfaces High Build Acrylic Finishes Semi smooth paint in a thick and highly flexible layer Trowel on option offers fine to medium sand finish Maintains itself for long term protection Good for tall, hard to access buildings due to low maintenance Decorative Finishes Wood Float - done by skimming the final coat with a float to produce a smooth, dense surface Bagged Finish - rubbing a ball of damp hessian cloth into the surface Sponge Finish - mopping or sponging the unhardened surface with damp sponge Control Joints Cement render cracks from shrinkage as render dries Cracking may occur when the background moves or where substrate material change Joints are located where movement may occur to break up large render areas Metal Lath Used on areas of weakness such as external corner to reinforce render where the substrate is insufficient in terms of cracking Protects against shrinkage Downloaded by isabella ricchiuti ([email protected])  lOMoARcPSD|48705191 Curing Render should not dry quickly - causes shrinkage and cement doesn't hydrate properly All coats should be kept damp for 3 days or until next coat Downloaded by isabella ricchiuti ([email protected])