Traditional Roofing Materials

• Before railways, local materials dictated roof construction.

Pitched Roofs

Thatch

• Common in lowland areas such as Norfolk and Suffolk.
• Long, straight water and marsh plant stalks such as reeds are cut, dried, bound, and layered.
• Rainwater drains effectively.
• Excludes wind and is a good insulator.
• Readily ignites and burns quickly.
• May house small birds, rodents, and insects.

Tiles

• Clay from midland and southern England is suited for pressing and burning into tiles.
• A readily available material for small, thin roof coverings.
• Flat, overlapping tiles effectively drain rainwater.
• Accommodate structural, moisture, and thermal movements.
• The numerous joins do not effectively exclude wind.
• Tiles are not good insulators individually.

Slates

• Rocky upland areas like Cornwall, Wales, northern England, and parts of Scotland use rock beds split into plates as roofing.
• Welsh slates are thin and uniform, suited for standard sizes.
• Cornish, Westmorland, northern England, and Scottish rocks are thick, uneven slabs.
• Laborious and wasteful to cut.
• Often used in random sizes, described as stone tiles.
• Overlapping slates effectively drain rainwater.
• Accommodates structural, moisture, and thermal movement.
• Do not exclude wind or insulate well.
• Railway development allowed common roofing materials to be used beyond their original areas in the 19th century.
• The pitch of tile and slate coverings determined roof forms for centuries.

Flat Roofs

Bitumen Felt and Asphalt

• The fashion for flat roofs led to the use of bitumen felt and asphalt in the 20th century.
• Two or three layers on timber or concrete roofs achieved success with renewals every 20-25 years.
• There was no requirement to insulate buildings initially.
• Statutory insulation requirements necessitated insulation layers formed under flat roof coverings.
• Temperature fluctuations caused felt and asphalt to deteriorate.
• Energy conservation and insulation led to rebuilding flat roofs as pitched roofs.

Low Pitch Roofs

• Low pitch roofs (5-10°) became fashionable for single-story buildings as a revolt against pitched roofs.
• Too shallow for tiles or slates.
• Sheets of non-ferrous metals like copper and aluminum were used instead.
• Joined with standing seams down the slope and welted seams across it.
• Used as a weather surface for arched and curved concrete roofs.
• Appearance and durability justified the material costs.

Functional Requirements of Roofs

• New houses often use tile or slate-covered pitched roofs due to preference.
• Roofs should have strength, stability, weather resistance, durability, and fire safety.
• They should also resist heat and sound passage.
• Roof strength and stability depend on materials and formation.

Flat Roofs

• Flat roofs can be timber, metal, or concrete platforms usually horizontal or inclined up to 5°.
• Adequate support from walls or beams is necessary.
• Sufficient depth and thickness are needed to avoid deflection.

Sloping Roofs

• Sloping roofs have an inclination of 5° to 10°.
• They may be a sloping platform or shallow frame.
• The monopitch and butterfly roofs use shallow trussed rafters.
• Butterfly roofs depend on a central support beam.
• A monopitch roof with sloping soffit is built like a flat roof inclined out of horizontal.
• Imposes lateral pressure on the wall under the lowest edge.

Pitched Roofs

• The word 'pitch' describes the angle of rafters pitched more than 10° to a ridge.
• Traditional pitched roofs have equal slopes rising to a central ridge.
• Typical construction involves triangular frames of sloping rafters tied with ceiling joists.
• Struts and ties may be added for economy and rigidity.
• Strength depends on the depth of the triangular frames at mid-span.
• Instability across slopes requires bracing using gable end walls, hipped ends, or diagonal roof boarding.
• Lean-to roofs are monopitch roofs supported by an external wall and walls enclosing an annexe.

Resistance to Weather

• Roof materials vary from impermeable asphalt to overlapping clay tiles.
• Smaller units like tiles or slates require a greater pitch to exclude rain.
• Larger units like profiled sheets can be laid at lower pitches.
• Impermeable materials like asphalt and bitumen can be laid flat.
• Sheet metals like lead and copper can have shallow falls.
• Small, open-jointed tile and slate require felt or paper to exclude wind.
• Roofs are exposed to movements due to wind, snow, temperature, and moisture.
• Traditional materials like slate and tile accommodate movements without breaking or leaking.

Durability and Freedom From Maintenance

• Durability depends on ability to exclude rain, snow, and frost.
• Water penetration can cause decay, corrosion, or disintegration.
• Traditional slates and tiles, properly laid, last many years with little maintenance.
• Variations in shape, color, and texture are attractive features.
• Machine-made slates and tiles are less pleasing in appearance.
• Non-ferrous sheet metals (lead, copper, zinc, aluminium) last long with little maintenance.
• The appearance is not familiar in most buildings, there is no consensus of opinion on their appearance.
• Asphalt and bitumen felt are short to medium-term materials (20-30 years) that oxidize.
• Flat roof coverings are not generally deemed to be attractive.

Fire Safety

• Building Regulations focus on safe occupant escape.
• Requirements are minimal for most roofs, assuming ignition occurs after escape.
• Regulations do limit external fire spread across roof coverings.
• Bitumen felt encourages flame spread unless covered with stone chippings, tiles, sand, or screed.

Resistance to the Passage of Heat

• Roof materials and coverings are often poor insulators.

• Insulation is needed against heat loss or gain.

• Recommended max U-value for dwellings is 0.25 W/m²K.

• The most economical is insulating between ceiling joists.

• The insulating layer reduces heat loss and gain.

• Uninsulated roof spaces require insulation for water storage and pipes.

• Storage space in a roof may need insulated roof slopes.

• Ventilation might be needed to reduce moisture on cold surfaces.

• Warm climates often ventilate to reduce inside roof temperature.

• Insulation at ceiling level creates a "cold roof."

• Insulation across roof rafters creates a "warm roof."

• The roof space below rafters doesn't need ventilation.

• Insulating flat roofs can be applied to the underside or top or in between joists

• Rigid materials that serve as a rood deck can have insulation boards layed on top

• Position for insulation depends on roof type, material, fixing ease, and finish.

• Practical place for insulation is on top of timber or concrete, under covering.

• With insulation on top of the roof deck, the structure maintains inside air temperature.

• Very considerable temperature fluctuations at the material on the covering will require

• Tar and bitumen coverings can quickly oxidise

• Inverting/insulating roof on top will protect from temperature fluctuations

• With insulation below, structure is subject to temperature fluctuations leading to "cold roof."

• Disadvantage of cold roofs is moisture vapour that can affect performance.

Vapour Check

• Vapour checks are some impenetrable material (like polythene sheeting) and are used to control movement of moist air.

• The term 'barrier' is avoided because a complete seal is impractical for most roofing applications.

• Insulating materials like extruded polystyrene serve as a vapour check if properly fitted.

Resistance to the Passage of Sound

• Sound resistance not a concern unless building is near a busy airport.
• Roof mass is main factor.
• A solid concrete roof is more effective than a similar timber roof.
• Mineral fibre slabs, batts, or boards have some effect to reduce noise.

Pitched Roofs

• Most pitched roofs are symmetrical with equal slopes pitched to a central ridge. The term is used to describe the parts of a pitched roof (see Fig 161)
• Minimum roof slope is determined by the minimum slope necessary to exclude eaves gutters.
• ridge. Eaves is a general term to describe the lowest part of a slope
• roof slope gutters. The term used to describe the parts of a pitched roof are
• gable end roof. Eaves is a general term to describe the lowest part of a slope
• ridge. The ridge The traditional pitched roof is constructed with slopes pitched at angles
• valley roof. Eaves is a general term to describe the lowest part of a slope

Couple Roofs

• Basic pitched roof structure with timber rafters pitched to a ridge.
• Rafter pairs are nailed to a central ridge board.
• Cannot exceed 3.5 m span.
• Foot of rafter bears on and is nailed to a timber wall plate.
• Spread, tending to overturn.
• Using metal bars increases the limit to 5 mm span.
• Rafters are spaced at 400 to 600 mm apart.
• 100mm deep by 38mm thick.

Ridge Board

• Provide means to fix the top of pairs of rafters.
• Softwood board with its long axis vertical and its length horizontal
• The depth of the ridge board is usually some 50 mm deeper than required as bearing for rafter ends, to provide fixing for battens.

Wall Plate

• Bedded in mortar on walls
• Provides support and fixing for the foot of rafters.
• A birdsmouth cut is made in the top of each rafter
• Rafters are nailed to the wall plate.
• The bearing of the rafter ends on the wall plate does not effec- tively resist the tendency of a couple roof to spread under load

Close Couple Roof

• Pitched roofs to small buildings framed with horizontal ceiling joists nailed to the side of the foot of each pair of rafters.
• Ceiling joists tie rafters.
• 38/50mm thick usually.
• 97 to 220m deep often.
• Max span between is 5.5m
• Advantage has interior space
• Requires substantial timbers

Collar Rod

• Most one third up the height of roof, tied couple roof (Fig 167 illustrates)
• Purpose is too allow room use of the roof that has space (limit on the largely roof unused)
• Doesn’t tie effective as a joint ceiling as a do joint that fixed the foot of rafters to a pairs does.
• Is limited to is this roof limited to span of maximum 4.5 m

Purlin Roof

• Purlins provide intermediate rafter support.
• These horizontal timbers are supported by end walls or internal loadbearing walls.

Hipped End Roof

• The ends of pitches that meet the sides.
• Provides a fixing support for rafter of legs

Angle Tie

• Cut from 100 x 75 mm timbers that are bolted.
• Usually from the hip that in end.
• End provide that provide main the stability,

Valleys

• The internals are an angle junction.

Trussed Roof

• Tie, mean that word trussered the (also being together tied)
• Used with a connectors iron galvanized bolting that, trusses timber were. (Mostly and connection)
• The truss that provides is strength its the connectors, at.
• Truss the can designed is timbers each with to frames
• Also that support struts with that provides for it through support provides

Trussed Rafter Rood

• The timbers that and light the fabrication
• And timbers of The unitize frames (or they by and are to nailed a be the (this side
• The unitize frames (or they by and are to nailed
• The is a also for is that is also, for has rafter
• The this by for it is that is
• In this also better there

Eaves

• Is usually a general and the the the lower described
• Eaves (the, so it and covering that, shed small The The purpose is of
• Is an area the (but in and can) Is the
• These, to will or for

Dormer Windows

• The structure vertical and or that has in this

Sheet Metal Covering to Low Pitch Roofs

• Fashionable of the low 20th been
• This from with better with not well The is Is and of good with has to as it as with
• That that has that has (usually it in a be the)

Standing Seems

• The seems at joints a the Copper with is often copper And it

Sheet Lead

• the The tear can and been, its has
• This with on and lead lead

Copper Sheet

• With for a in one has had lead sheet

Zinc Sheet

• To a a sheet steel

Waterproof Membrane for Timber Flat Roof

• Asphalt

Building up Bitumin

• With then by with (the that that has)