SITEWORK STANDARDS
EXTERNAL WALLS - TOLERANCES
Some of the materials used to construct external walls are not uniform because of their manufacturing process, nor are they intended to be. In consequence, some external walls will have variations and irregularities. Where reclaimed materials are used there may be even greater irregularities and these characteristics are often intended as an aesthetic feature. The recommended tolerances are intended to be applied in the spirit of this overall context.
Commentary
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bricks and other materials vary in size and appearance for a number of reasons and in consequence the tolerances and finishes stated may not always be appropriate, especially where reclaimed stock is used. Such materials will need to be considered separately
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the tolerances described generally apply to entire areas of walling, complete panels and the like, and not to the elements of the construction, such as individual bricks
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the toleranaces do not apply to design features and similar constructional details which are not intended to lie within the limits stated in this document (e.g. quoins, soldier courses, plinths).
Items to be taken into account include:
Fairfaced masonry
(a) level of bed joints
± 8mm maximum deviation for walls 5m long (a pro rata tolerance is applicable for walls less than 5m long).
± 12mm maximum deviation for walls over 5m long.
(b) thickness of bed joints
The thickness of an individual bed joint should not vary from the average of any 8 successive joints by more than 5mm.
Commentary
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bricks and other materials vary in size and therefore some variation in the thickness of bed joints is likely.
(c) straightness on plan
± 8mm maximum deviation in any length of wall up to 5m.
(d) perpend alignment in external walls
Vertical alignment of perpend joints should not deviate significantly from the perpendicular.
Commentary
- because bricks do vary in length as a result of their manufacturing process, not all perpend joints will align. However, there should not be a cumulative displacement of the perpend joints in a wall.
(e) plumb of wall
Maximum 8mm out of plumb for walls up to 5m in height, limited to 8mm in a storey height (approx 2.5m).
Maximum 12mm out of plumb for walls over 5m in height, limited to 8mm in a storey height (approx 2.5m).
(f) straightness in section
± 8mm maximum deviation in any 2.5m height of wall.
(g) straightness of external reveals
4mm maximum deviation.
Render
(h) vertical and horizontal flatness
±8mm maximum vertical and horizontal deviation from flatness in 5m (excluding features).
Commentary
- areas of render in close proximity to features (e.g. bell casts),are excluded from the tolerance
- flatness is measured in a similiar way to straightness on plan and plumb of masonry.
Curtain walling
(i) line, level, plumb and plane
± 2mm maximum deviation in any one storey height or structural bay width and ± 5mm maximum deviation overall.
These tolerances apply unless otherwise specified in the design.
Rainscreen cladding
(j) line, level, plumb and plane
± 3mm maximum deviation in any one storey height or structural bay width.
These tolerances apply unless otherwise specified in the design.
Brick slip cladding systems
(k) vertical and horizontal flatness
± 8mm maximum vertical and horizontal deviation from flatness in 5m.
(l) level of bed joints
± 8mm maximum deviation in the bed joints in a 5m length (a pro rata tolerance is applicable for walls less than 5m long).
EXTERNAL WALLS - APPEARANCE
1.2 - S2 External walls shall have an appropriate appearance
Appearance should be considered for entire wall areas, panels, interfaces and the like and not for individual units. Consequently, the wall being considered should, where possible, be viewed in daylight from a distance of not less than 10m.
Some variation in colour and texture of external walls is inevitable and in certain cases is a feature.
Items to be taken into account include:
Fairfaced masonry
(a) appearance of fairfaced masonry
Fairfaced masonry should be reasonably uniform in texture, finish and colour. Excessive colour banding should not occur.
With certain walls, such as half brick walls, a fairfaced finish can only be achieved on one face. The other face should be left neat and tidy.
Mortar should be reasonably uniform in texture, finish and colour.
Facing brick units should not have significant cracks in them or other damage such as chips and marks greater than 15mm in diameter.
Commentary
- some mortar blemishes will occur on individual masonry units
- some variation will occur in the texture, finish and colour of mortar
- some variation will occur in the colour of individual masonry units and generally over the wall
- colour banding of fairfaced masonry should be avoided by mixing batches and consignments of bricks
- efflorescence occurs naturally in some types of masonry. It is not harmful and usually disappears over time
- some brick products have natural or design features which may be in excess of 15mm in diameter
- some minor shrinkage cracking may occur between masonry units (bricks and blocks) and mortar joints.
Render
(b) apearance of render
Rendering on walls should be reasonably consistent in texture, finish and colour.
Commentary
- some hairline cracking and crazing is likely to ocurr in both traditional render and proprietary render systems. Such cracking and cracking should not impair the performance of the render
- crazing, which may occur in the render surface, should not be more than 0.2mm wide
- there may be some colour variation in appearance. This may be due to differences in suction of the background and orientation of the wall
- daywork joints, patching and other repairs may be visible but should not be unduly obtrusive.
Curtain walling
(c) appearance of curtain walling
Installation should ensure that curtain walling systems are within reasonable tolerances and appearance for the materials involved.
Rainscreen cladding
(d) appearance of rainscreen cladding
Installation should ensure that rainscreen cladding systems are within reasonable tolerances and appearance for the materials involved.
Brick slip cladding systems
(e) appearance of brick slip cladding systems
Installation should ensure that brick slip cladding systems are within reasonable tolerances and appearance for the materials involved.
Timber cladding
(f) appearance of timber cladding
Some variation in colour may occurr in uncoated timber exposed to the weather.
The rate and extent of colour change will vary between species and can sometimes vary even within the same species.
Commentary
- the effects of normal weathering may cause certain uncoated timber, over time, to develop a silver/grey colour.
Tile hanging
(g) appearance of tile hanging
Panels of tile hanging should be reasonably uniform in appearance, particularly at abutments.
Commentary
- certain handmade tiles vary in size and may not be of a uniform appearance
- some variation in colour may occur in tiles.
Cast stone sills
(h) appearance of cast stone sills
Conspicuous surface abrasions and chips caused during installation should be removed in accordance with the manufacturer's recommendations which may include filling, polishing out, re-spraying or painting as appropriate.
Commentary
- cast stone is manufactured with natural products and colour variations are inevitable
- efflorescence, fungicidal growth and colour variation may occur due to orientation, shading and pollution.
EXTERNAL WORKS
1.2 - S3 External works shall have appropriate finishes
Items to be taken into account include:
(a) drives, paths, decks, terraces and balconies - variations in surface finish
Variations in the surface should not exceed ± 10mm maximum deviation from a 2m straightedge with equal offsets provided correct gradients have been used.
Commentary
- some minor variations in surface levels including scuffing and pitting may arise due to settlement, natural ground movement and car and light vehicle use. In gravel and other loose surfaces, displacement of stone etc. will occur
- localised falls into gulleys and channels are acceptable.
(b) drives, paths, decks, terraces and balconies - standing water
Surfaces should minimise the potential for standing water.
Commentary
- one hour after rain has stopped, areas of temporary standing water should not be deeper than 5mm or exceed 1m² . Temporary standing water is not permitted adjacent to entrance doors.
(c) covers to drainage systems
Covers to the drainage system should align with the adjacent ground or surface finish.
Covers to drainage channels should be set below the adjacent ground.
Commentary
- in hard landscaping, some settlement of the area immediately around the cover may occur. The difference in height between a cover and the adjacent hard surfaces should be set to allow for future settlement
- in soft landscaping, such as lawned areas, some settlement of the ground may occur.
DOORS AND WINDOWS
1.2 - S4 Doors and windows shall be installed to appropriate tolerances
Items to be taken into account include:
(a) openings in walls (including external openings viewed from the inside)
(b) gaps and distortion
Glazing
1.2 - S5 Glass shall be free of undue defects
The following are acceptable if they are neither obtrusive nor bunched:
- bubbles or blisters
- hairlines or blobs
- fine scratches not more than 25mm long
- minute particles.
The above does not apply within 6mm of the edge of the pane, where minor scratching is acceptable.
Commentary
- glass should be viewed in daylight from within the room and at least 2m from the panes (3m for toughened, laminated or coated glass) facing the glass.
WALLS AND CEILINGS - TOLERANCES
1.2 - S6 Wall and ceiling finishes shall be built to appropriate tolerances
Items to be taken into account include:
Plastered and dry lined
(a) wall and ceiling surfaces
The deviation of board joints in walls and ceilings should not exceed 3mm when measured using a 450mm straightedge with equal offsets.
Duct casings
(b) squareness
Skirtings
(c) gaps
The gap between the floor finish (without coverings) and between the bottom of the skirting should not exceed 5mm.
Commentary
- the gap between the floor finish and the skirting may increase because of normal drying out, shrinkage and/or deflection, particularly in timber floors
- a gap may occur between the wall finish and skirting due to drying out, shrinkage and fixing position.
WALLS AND CEILINGS - APPEARANCE
1.2 - S7 Wall and ceiling finishes shall have an appropriate appearance
Items to be taken into account include:
Plastered and dry lined
(a) appearance of wall and ceiling surfaces
Surfaces should be reasonably uniform although there may be minor textural differences around lights and other fittings. There should be no visible gaps between fittings and the wall/ceiling (e.g. around switch plates).
In plastered walls and ceilings some tooling marks may be visible.
Commentary
- in general wall surfaces, some cracking (up to 2mm wide) is likely due to shrinkage and differential movement of materials
- at wall, floor and ceiling junctions where there are changes in the construction materials, small cracks (up to 2mm wide) may appear in the surface as a result of shrinkage and differential movement of materials
- jointing tape should be fully covered and not be obtrusive in the finished wall or ceiling surface
- small cracks may occur in wall finishes which pass across floors (e.g. in staircase walls)
- where stair strings abut a wall, a crack of up to 4mm may appear as a result of shrinkage of materials.
Duct casings
(b) appearance of duct casings
Duct casings, access covers and any associated framing should be neat and tidy and have an appropriate decorative finish.
Blockwork walls in garages
(c) appearance of blockwork walls in garages
Cracks (up to 2mm wide) in unplastered blockwork walls may be evident due to thermal movement and drying shrinkage.
Skirtings
(d) joints
Joints in skirtings are likely in long lengths of walls. Joints should present a continous appearance when viewed from a distance of 2m in daylight. Some initial shrinkage of the skirting may already be evident at completion of the property.
Commentary
- gaps in skirtings may appear at joints and corners due to shrinkage.
FLOORS
1.2 - S8 Floors shall be built to appropriate tolerances
Items to be taken into account include:
(a) level of floor
Maximum 4mm out of level per metre for floors up to 6m across, and maximum 25mm overall in any other case.
Commentary
- the effects of normal drying shrinkage on screeded floors may cause minor cracking
- timber floors and staircases naturally shrink as they dry. As this drying occurs, it may result in squeaking components as they move against each other. This is natural and to be expected, and cannot be totally eliminated.
(b) flatness of floor
±5mm maximum deviation from a 2m straightedge with equal offsets.
(c) underfloor service ducts
Service ducts should be constructed so that the cover is level with the adjacent floor finish provided by the builder.
Commentary
- drying shrinkage of the floor may result in minor differences in level between the floor and duct cover. This may become evident with some types of thin floor coverings, and the choice of covering should take this into account.
CERAMIC,CONCRETE,TERRAZZO AND SIMILIAR TILE FINISHES
1.2 - S9 Tiling shall have an appropriate appearance
Items to be taken into account include:
(a) tile joints
Tile joints should be straight in alignment unless the tiles are, by design, irregular in shape.
The width of floor tile joints should not be less than 3mm, unless otherwise specified by the manufacturer.
The width of wall tile joints should not be less than 1mm. This relieves any local stress that may occur.
Joints in floor tiles should generally not exceed the tile thickness, but wider joints, up to 10mm, may be necessary to accommodate dimensional irregularities in some tiles.
Where tiles have dimensional irregularities the joint dimensions should be "evened out" to maintain a regular appearance.
(b) overall variation in surface level of wall and floor tiles
± 3mm maximum deviation from a 2m straightedge with equal offsets.
(c) variations in surface level between adjacent wall or floor tiles
1mm for joints less than 6mm wide.
2mm for joints more than 6mm wide.
JOINT SEALANTS
1.2 - S10 Joint sealants shall have a neat and tidy appearance
Items to be taken into account include:
(a) appearance of joint
Sealants should be tooled to remove blisters and irregularities, and achieve a compact, smooth neat surface finish.
Commentary
- joints should normally be viewed from a distance of 2m (e.g. external window and door frames), but may be less depending on the location (e.g. showers and baths).
OTHER SURFACES AND FINISHES
1.2 - S11 Other surfaces and finishes shall have an appropriate appearance
Items to be taken into account include:
(a) painted and varnished surfaces
Surfaces should be reasonably smooth and free from nail holes, cracks and splits. Open joints should be filled. Colour, texture and finish should be reasonably uniform.
Commentary
- surfaces should be viewed in daylight from a distance of 2m and not by shining artificial light on the surface. Wall lights or uplighters should be switched off
- painted and varnished surfaces should be free from conspicuous runs and prominent brush marks. There should be no bare or starved areas
- timber surfaces may show limited raised grain and the colour and texture may also vary
- drying shrinkage of timber may cause cracking of the paint finish, particularly where joints occur in plaster and woodwork
- where painted surfaces are touched-up, minor colour variations will occur
- external finishes will dull over time depending on a number of factors such as exposure to sunlight, rain and pollutants.
(b) knots in timber
Some exudation of resin from knots may occur and may cause discoloration of paintwork, both internally and externally.
Commentary
- because timber is a natural material some resin is likely to exude from knots even though modern primers contain a knotting compound to limit the effect.
(c) garage floors
Where garage floors have not been sealed, dusting may occur.
(d) socket, switch and other service outlets
Where there are two or more adjacent outlets they should be aligned horizontally.
FITTED FURNITURE
1.2 - S12 Fitted furniture shall have an appropriate appearance
Items to be taken into account include:
(a) appearance
Doors and drawers of fitted furniture should be visually aligned vertically, horizontally and in plan, and operate as intended by the manufacturer.
Gaps between adjacent doors and/or drawers should be uniform.
There should be no significant difference in level at the intersection of adjacent worktops.
Commentary
- no dimensional tolerance has been set for gaps between adjacent doors and/or drawers or for their alignment because some variation will be necessary to take account of adjustments as part of the fitting process
- no dimensional tolerance has been set for the abutment of adjacent worktops because of the variety of materials available and because minor variations, even with manufactured products, are inevitable and small differences in height may be unavoidable
- fitted furniture should normally be viewed from a distance of 2m.
(b) scratches
Factory-finished components should not have conspicuous abrasions or scratches when viewed in daylight from a distance of 0.5m.
Commentary
- conspicuous surface abrasions caused during installation should be removed in accordance with the manufacturer's recommendations which may include filling, polishing out, re-spraying or painting as appropriate
- in rooms or areas where there is no daylight, scratches should be viewed in artificial light from fixed wall or ceiling outlets and not from portable equipment.
