Floor Functional Requirements

Functional Requirements of a Floor

• Floors must have strength and stability, resistance to weather and ground moisture, durability and be easy to maintain, fire safety, and resistance to heat and sound.

Strength

• Floor strength depends on the material characteristics such as timber, steel, or concrete.
• The floor structure should sufficiently support the floor's dead load which includes finishes, fixtures, partitions, services as well as the imposed loads of occupants, furniture, and equipment.
• BS 6399: Part 1 provides the Code of Practice for assessing dead and imposed loads in buildings.
• Timber floor construction is typical for small imposed loads like single-family homes with no more than three stories.
• Lightweight timber floors are adequate for small loads over short spans, and are cheaper than reinforced concrete.
• Reinforced concrete offers both support strength and fire resistance for larger loads and wider spans.
• Approved Document A outlines recommended sizes and spacing for softwood timber floor joists of two strength classes.

Stability

• Floors act as horizontal surfaces designed to support people, furniture, equipment, or machinery.
• Adequate floor stiffness is needed to maintain stability and remain horizontal under dead load, other supported fixtures, and anticipated loads.
• Floor structure should accommodate electrical, water, heating, and ventilation services, either within its depth or above/below, without impacting stability.
• Stability requires adequate support and stiffness against deflection under load.
• A deflection of 1/300 of the span is generally acceptable as a max in floor designs.

Resistance to Weather and Ground Moisture

• Ground floors, especially in heated buildings, encourage moisture from the ground to rise which can cause dampness.
• Moisture transfer from the ground promotes wood rot that causes damage to timber floors and finishes.
• Moisture penetration depends on subsoil, water table, and site slope; gravel or coarse sand bases with low water tables have little penetration, while clay bases with high water tables will have significant moisture transfer.
• A concrete slab might suffice where moisture penetration is low, but a waterproof membrane on, in, or under the slab is required otherwise.

Durability and Freedom from Maintenance

• For durability, floors and finishes should last the building's expected life with minimal upkeep which depends on the materials used.

Fire Safety

• Suspended upper floors should provide fire resistance allowing building occupants to escape.
• Building Regulations define fire resistance from .5 to 4 hours, depending on building size and usage.
• Timber floors generally have less fire resistance than reinforced concrete.
• Timber floors provide adequate fire resistance in small residential buildings, while concrete floors are necessary in large buildings.

Resistance to the Passage of Heat

• Floors should resist heat transfer; insulation and U-values equivalent to an exposed wall are required where temperature differences exist.
• Ground floors should minimize heat transfer using hardcore and damp-proof membranes.

Resistance to the Passage of Sound

• Floors separating dwellings or activities act as sound barriers
• Timber floors transmit sound more readily than concrete floors, so concrete is typically used between dwellings.
• Sound transmission resistance of timber floors improves by filling spaces between joists with insulation.

Concrete Ground Floors

• Most ground floors use ground-supported in-situ cast concrete slabs on a hardcore bed with a damp-proof membrane and insulation.

Ground Supported Slab

• Solid basement floors are supported from the ground on which they are built
• Stability of such floors is reliant on the concrete under them
• For small domestic loads, the concrete without reinforcement, provides adequate stability

Suspended Concrete Slabs

• Form the ground floor as a suspended reinforced concrete slab, supported by external and internal load-bearing walls, independent of the ground, where the ground is sloping or has poor bearing capacity.
• Use pre-cast reinforced concrete plank, slab, or beam and block floor systems, since there is no ready means of constructing centering on which to cast an in-situ concrete floor.
• A one way spanning, pre-cast concrete floor should bear on internal & external walls with endbearing of at least 90mm and built into the walls

Damp-proof Membrane

• A DPM may not be necessary where suspended ground floor slabs are above ground level with an ventilated air space of at least 75 mm below the underside ventilation to prevent the build-up of stagnant air.

Insulation

• A space below should be at least 150 mm and ventilation should operate on opposite sides of the space where gas could accumulate which might result in an explosion
• DPM under the screed is recommended where the ground level is below the surrounding level or the site has slopes to prevent a buildup of moisture
• Insulation reduces heat transfer and maintain comfortable temperatures when ground floor spaces may become damp

Floor Surface

• The term is generally used to describe the top surface of a structural floor.
• The level surface of a structural concrete layer serves as the floor surface.
• Concrete and timber board elements can act as the surface.
• Floor finish describes materials applied to a surface for a finished look, such as tiles or plastic sheets.
• For sheds, workshops, stores, the finished top surface of the oversite concrete acts as the finished floor surface.
• Concrete is not generally satisfactory as a finished surface
• Extensive areas of concrete floor may be levelled and finished by power floating as a satisfactory base for thicker floor finishes such as mastic asphalt, tiles and wood blocks.

Floor Screeds

• Screeds provide a level surface to which a floor finish can be applied; screed strips are carefully leveled in both directions to create a precise finish, the main bulk is then spread and leveled between the screeds.
• Cement, sand, and water are screed materials, they are spread, compacted, leveled, and troweled
• Screed laid on a concrete base within 3 hours of placing will bond strongly and dry slowly so drying shrinkage and cracking will be minimized
• A screed on a concrete base should be at least 40 mm thick
• A screed laid on an impermeable dpm the screed should be at least 50 mm thick
• A screed layered on compressible thermal/sound insulation should be at least 65 mm thick for domestic use, or 75 mm thick for others
• For screeds up to 40mm, a mix of Portland cement and clean sand using proportions by weight 1:3 to 1:4.5 should be used
• For screeds over 40mm, a fine concrete mix using proportions by volume 1:1.5:3 of cement, fine and coarse aggregate is used
• To ensure workability, screed should be mixed with a sufficient amount of water
• The material is spread over the base and is compacted by tamping it to its required thickness and level, prior to being finished with a wood or steel float
• Premixed cement screed materials, dry bagged ready for use on the site avoid messy site mixing

Floor Surface Finishes

• Traditional flooring was composed of stone slabs, clay tiles, or brick set on a bed of lime and sand.
• Timber provided insulation against cold and damp rising from the ground; boards attach to battens set in the earth base or set in the concrete
• A solid concrete floor allows for the easy application of floor finishes.
• Flooring materials include clay tiles, linoleum, plastic, stone, and rubber.
• More recently, plastic floor finishes have lost favor, leading to a return to more "traditional" materials, such as linoleum, clay tiles, stone slabs, and timber.

Floor Finishes for Concrete Floors

• Generally, floor finishes should be level, resistant to wear, and easily cleaned; specific areas need non-slip surfaces, smoothness for polishing, resistance to spillage, seamlessness for hygiene and freedom from dust
• Small rooms in houses/flats are chosen based on cleansibility
• Offices, public institutional buildings are chosen based on ease of cleaning with power operated equipment

Broad classification of Floor finishes

• Jointless
• Flexible thin sheet and tile
• Rigid tiles and stone slabs
• Wood and wood based

Jointless floor finishes

• Encompasses cement- and resin-based screeds and mastic asphalt
• Cement floors with sand serve as low-cost finishes for garages, stores, and outhouses

Fibre Reinforced Cement Screed

• Fiber reinforces against drying, shrinkage, and cracking.

Surface Hardeners

• These materials are added to cement to improve surface resistance to wear and penetration of oils and grease

Granolithic Paving

• Consists of a crushed granite mixture carefully sieved so particles are graded from coarse to fine and will be particularly free of voids or small spaces
• If laid as soon as the oversite concrete is hard enough to stand on, only 15 mm can be used.
• clean the surface of newly laid concrete thoroughly by mechanical hacking to remove the surface layer to expose aggregate

Anhydrite Floor Finish

• They must be applied to a dry floor due to their high rate of water absorbentency; not appropriate in damp, wet environments
• Anhydrite hardens without shrinking
• Premixed bagged screed material is a floor finish

Resin Based Floor Finish

• Used where durability, chemical resistance and hygiene are required, such as laboratories and hospitals
• It is made up of epoxy resins as binders with cement, quartz, aggregates and pigments and is spread at thicknesses of up to 12mm
• Resin Emulsion Finishes are not meant for use in small, domestic or home offices

Polymer Resin Floor Surface Sealers

• Specialist floor finishes (thin) are used for their resistance to water, acids, oils, alkalis and some solvents
• Polyester, epoxy or polyurethane resin floor sealers are an example

Mastic Asphalt Floor Finish

• It serves both as water- and vapor-proofing and as floor finish
• Lightweight, hardwearing, dust free, and easy to clean but liable and potentially slippery when wet

Flexible Thin Sheet and Tile

• Linoleum is made from oxidized linseed oil, rosin, cork or wood flour, fillers, and pigments compressed on a jute canvas backing
• Usually laid with butt joints

Flexible Vinyl Sheet and Tiles

• Polyvinylchloride is a thermoplastic used for flexible sheets and tiles as a floor finish
• Resistance to wear and flexibility depend on vinyl content
• Used with a thin bed of epoxy resin adhesive to ensure adhesion

Flexible Rubber Sheets

• Natural or synthetic
• Vulcanized rubber with fillers and pigments
• Bond to a screeded/power floated surface using epoxy resin adhesive w/roller

Rigid Tiles and Stone Slabs

• Can be described as Clay Floor Tiles or Floor Quarries
• The term Quarry is derived from the french "carre" relating to square

Clay Floor Tiles

• Natural clay tiles have been used for centuries as hard, durable flooring options
• The thicker types of tiles are set onto beds of consolidated ground + thiner tiles are set with beds of sand

Floor Quarries

• Have been manufactured in Staffordshire and Wales
• If the clay is of good quality then the tile will be very hard, strong and long lasting

Plain Colours

• Uses natural clays known for their purity to eliminate water use and limit shrinkage which is caused during burning

Vitreous Floor Tiles

• They have a smooth surface that is water resistant
• Tiles are uniform in shape, having smooth semi-gloss or gloss surfaces that do not absorb water or other liquids to which would allow liquid to be easily cleaned with floor mops instead.

Considerations for Laying Clay Tile Choices

• Provision of a material into which the tile may be laid into to take up variations in tile thickness and produce level finish
• Good adhesion to the base for solid support to avoid cracking
• Means of accommodating relative structural, moisture and thermal movements between components

Direct Bedding Method

• Is done on a layer of wet cement and sand spread over a screeded or level finish concrete floor

Separating Layer Method

• Some instances of tiling produce a “arching” in the center due to expansion or contraction of materials relative to each other

Thin Bed Adhesive Method

• Most modern tiles are bedded and laid on and adhesive that is primarily a bond between the tile and the base

Properties of movement joints

• The joints between the tiles and slabs can accommodate some movement of the floor finish to bedding and the concrete floor
• For large structures should be carried through rigid floor finishes
• Joint failures occur from cement rich mixes shrinking

Types of movement joint

• Provide a workable mix by using a small amount of cement and water for minimal drying shrinkage
• Recommendation to form movement joints around the perimeter of floors with elastic sealant

Advantage and disadvantage of joints

• The joint material will be softer and prone to wear on adjacent edges
• Use where necessary

Wood floor finishes Advantages

• Come from the variety, grain, and texture of the wood are the benefits for warm, resilient and relatively quiet flooring

Floor boards

• Both plain edge or tongued/grooved boards can be used

Wood strip flooring

• Boards should be cut in narrow strips to minimize loss of width and shape
• The tongue and groove is there to interlock ensuring there is no twisting

Advantages galvanised floor clips

• The battens and strips will have a fine and springy level of flexibility

Disadvantages of securing battens

• Moisture expansion causing deformation may lift batten and screed

Wood strip flooring and use

• Requires care, thus is suited when wear is only light, such as in a household setting
• Sanded, to remove thin top surface, and polished

Wood block floor finish

• Appropriate choice for heavy-wear surfaces since they provide moderately resilient floor surface texture.
• Blocks should be cut with a half dovetail incision, then the installer spreads a thin layer of bitumen to bind the blocks to the bitumen.

Suspended timber ground floor

• In past, houses with this type of floor was considered economical and satisfactory
• These floors are constructed using a timber platform over joist over columns that sit directly on the ground

Approved Document C Guidlines

• Requires certain measurements to be in place from ventilation access to height and thickness in construction

Wall plate guidelines

• Bedded in mortar upon dpc.
• To level, provide bearing surface and evenly distribute w/ point load

Types of floors:

• Wood floors – Fire and sound resistance is lacking
• Concrete – Greater resistance than timber for fire and sound
• Timber – Framed utilizing sawn softwood timber joists – Spacing depends upon dead and imposed loads
• Regularized joists used with rigid plasterboard for soffit
• To economize material, spans are laid across the least width of rooms

Double Floors

• Steel beams for intermediate support
• Beam is set into load bearing walls with pad stones

Strutting between joists

• Strutting between joists minimizes twisting or winding out of the vertical during timber shrinkage.
• Herringbone strutting: short pieces of timber are nailed between joists.

End Support of floor joists stability

• Ends of joists must be supported by beams or walls.
• Should be built into or across compartment walls where they may encourage spread of fire/ where ends may be persistently damp

Advantages of joist hangers

• Ends are not exposed to outside damp
• Reduced need for bricks around joists

Galvanised pressed steel hangers function

• Hangers used as an alternative to building in ends

Lateral restraint for walls

• Provision of lateral support is key
• Recommends use of strap and joist hangers to give support at each storey

Fire safety (structural floors)

• Required to meet a fire resistance rating
• The rating, to some extent, will depend on boards, joists, and ceilings used in design

Passage of Heat

• Must be insulated when exposed to the outside

Passage of Sound

• The greater the mass, the greater the reduction

Airborne Sound

• Transmission through floor by vibrations of air

Impact sound

• Disturbance brought on by object (such as footsteps) causing floor surface to vibrate.

To reduce transmission of airborne sound.

• Increases mass of the floor to restrict energy and reduce the amount of impact or disturbance
• The traditional method of insulating timber floors against sound is to spread a layer of plaster or sand on rough boards and nailed to a battens, sand on expanded metal, lath and plaster. Layer was called pugging.
• A resilient layer under the floor surface is used to deaden heavy impact
• A combination of resilient materials between levels helps to create a much greater floor design

Types of floors

• For concrete resistance depends on concrete mass

Timber floor components

– Consist of 18mm boards/chipboard, plasterboard, strips of mineral fibre etc.

Reinforced Concrete Upper Floors

• Reinforced concrete floors better resist damage by fire and safely support greater loads.
• Resistance to fire is greater than can be obtained with the use of a timber upper floor.
• Smaller building
• Self centering T-beams and infill blocks
• Hollow Beams
• Monolithic in situ cast floors
• The word centering is used to describe the temporary platform on which in situ cast concrete floors are constructed and supported