TECHNICAL

MANUAL
VERSION 11

20: TOLERANCES
20.
Contents
Functional Requirements
20.1.1 External Walls
20.1.2 External Walls continued

Tolerances 20.1.3
20.1.4
Internal Walls
Steel Frame and Timber Frame
20.1.5 Internal Floors and Ceilings
20.1.6 Windows and Door Frames
20.1.7 Finishes and Externals
FUNCTIONAL REQUIREMENTS
Limitations of Functional Requirements

1. These Functional Requirements do not and will not apply to create any policy liability for any remedial
works carried out by the contractor or otherwise, nor to any materials used in those remedial works (not
applicable to: ‘Ground Conditions’ guidance).
2. A more stringent tolerance may be stated within an existing National or European standard, however,
for the purposes of coverage under the relevant Warranty policy, where we have identified a tolerance
requirement, this would be deemed suitable to meet our Functional Requirements (not applicable to:
Ground Conditions, Foundations and Stairs guidance).
3. We only measure tolerances which are identified within this Technical Manual.

Workmanship

1. All workmanship must be within the tolerance requirements in this Section by a technically competent
person in a workmanlike manner so that the required finishes are achieved.

Materials

1. All materials should be suitable for the relative exposure of the building.

Design

1. The design and specification shall provide a clear indication of the design intent and demonstrate a
satisfactory level of performance.

© MD Insurance Services Limited 2023 448 Tolerances

20.
Tolerances
20.1
Tolerances
20.1.1 TOLERANCES: External walls
Method of measurement for straightness in section
Introduction Mortar bed joints ▪ The maximum deviation is +/- 8mm in any storey height, up to a maximum of
3m high.
▪ During construction, masonry units should be laid to ensure the wall will be Masonry bed joints should be satisfactorily straight, with the line of level taken
adequately: plumb, straight on plan and straight in section. along the top side of the brick or block. 25x25mm
▪ Tolerances and appearances should be considered for the entire wall not ▪ Level of bed joints should be +/- 8mm in any 5m length of wall; and, spacing block
individual elements of the construction. ▪ The thickness of a mortar bed should not vary from the average thickness of
▪ Assessment should be made in daylight conditions, and from a minimum 10m the next eight successive joints by +/- 1.5mm
distance from the element. Reference line
▪ Fair-faced masonry should be completed to a reasonable level, ensuring Measure and add 8 successive bed joints and divide by 8 to determine the
texture, finish and appearance are consistent. average size:
▪ A reasonable appearance for single leaf 102.5mm brick walls should be to
have one finished side only. A neat and tidy finish should be applied to the 11+11+12+9+10+10+12+9 = 84 Wall
other side.
▪ Mortar blemishes can occur on individual masonry units. Divide 84 by 8 = 10.5mm
▪ Efflorescence is naturally occurring in certain types of masonry. Its affects are
not harmful and the residue will generally disappear of its own accord over Therefore, the acceptable range of the bed joint below the 8 measured bed joints

Storey height (max 3m)

time. is 9-12mm
▪ Certain masonry products specified within the design have features and
marks inherent to their fabrication.
▪ Minor shrinkage may occur within masonry components. Horizontal +/- 8mm deviation Line of
▪ For fair face natural and cast stonework, finishes should be reasonably reference line for walls 5m long bed joint
uniform in colour and texture.
▪ Fungal growth, and colour variation may occur due to mitigating factors such
as the orientation of the wall, shading, and even pollution.

Tolerances for external facing masonry

External facing masonry includes: 5m (max)

▪ Facing brickwork and blockwork

▪ Natural stone
▪ Cast rough faced masonry Mortar perpend joints Method of measurement for plumb in section
▪ The maximum deviation from plumb in any storey height up to 3m, is a
Location of measurement Tolerance Vertical alignments of perpend joints should not deviate from the perpendicular to maximum of 8mm.
an extent which impairs the structural stability of the wall. ▪ Any walls over 3m height should be a maximum of 8mm from plumb in any
Mortar bed joint Level of bed joints should be +/- 8mm in any 5m storey, and no more than 12mm in total.
length of wall. ▪ Centre lines of perpends should be with +/- 15mm of the centre line to the ▪ Using 50mm spacing blocks the line of the masonry face in plumb must be
next 5 successive perpend joints; and between 42mm and 58mm from the reference line.
The thickness of a mortar bed should not vary ▪ Perpend joints within masonry panels between openings may be offset to
from the average thickness of the next eight accommodate setting-out. The perpend joints within the panel should not
successive joints by +/- 1.5mm. cumulatively displace more than the above tolerance. 50x50mm
spacing block
Mortar perpend joint Centre lines of perpends should be with
+/- 15mm of the centre line to the next 5
successive perpend joints. Reference line
Method of measurements for fair faced brickwork and
Straightness in plan The wall must be relatively straight in plan. A blockwork
maximum of +/- 8mm deviation in any length of
wall up to 5m. Wall
Straightness in section* The maximum deviation is +/- 8mm in any Method of measurement for straightness in plan
storey height, up to a maximum of 3m high. ▪ The wall must be adequately straight in plan. A maximum of +/- 8mm deviation
in any length of wall up to 5m.

Storey height (max 3m)

Plumb in section The maximum deviation from plumb in any
storey height up to 3m, is a maximum of 8mm. 5m (max)

Any walls over 3m in height should be a

maximum of 8mm from plumb in any storey,
and no more than 12mm in total.
Exterior window reveal The maximum deviation is 4mm per 1m straight
edge. 25 x 25mm
spacing block
* The method of measurement for fair faced natural masonry and cast rough
faced masonry is different to that of fair faced brickwork and blockwork. Please
see the additional requirements for the measurement of fair faced natural
masonry and cast rough faced masonry.

© MD Insurance Services Limited 2023 450 Tolerances

20.1.2 TOLERANCES: External walls continued

Additional requirements for the measurement of fair Exterior window reveal Render and cladding
faced natural masonry and cast rough faced masonry
Render
Rather than attempt to use the uneven face of the wall to determine tolerance, the ▪ Render should be applied to achieve a consistent texture, finish, and colour
finished face of the bed joint will provide the datum. This is based on the masonry in line with the designers proposed specification. Some variations in colour
units having a minimum 100mm mortar bed width, achieved at initial laying. appearance may occur due to variation in suction of the background surface
For the purpose of tolerance measurement, this cannot be raked or pointed to to the render, along with orientation of the wall.
reinstate tolerance. ▪ Completed and set render should be free from crazing (crazing is defined
within BS EN 13914-1 as being short, irregular and very fine cracks up to
▪ Temporary but rigid battens at the building angles are to be erected Max 4mm approximately 0.2mm in width). It is worth noting that some localised hairline
approximately 300mm away from the wall face. deviation cracking is likely to occur in traditional, and proprietary render systems.
▪ Lines are to be stretched between the battens. Limited cracking and crazing should not impair the performance of the home.
▪ There should be a constant distance maintained between the line and the bed ▪ Patching and other such repairs may be visible but they should be
joint subject to the permissible deviations. inconspicuous as possible in application.
▪ Where the render coat includes features such as bell-casts then tolerances
are not applicable at these locations.
approx. 1m straight ▪ The surface of the render should be within a maximum of +/- 4mm vertical and
300mm edge horizontal deviation when measured with a 5m straightedge.

Curtain Walling
Storey height (max 3m)

Design should allow for the line, level, plumb and plane of the completed curtain
wall to be within the acceptable tolerances of:
=
▪ Line: +/-2mm in any one storey height or structural bay width, and +/-5mm
overall.
Equal distance between ▪ Level: +/-2mm of horizontal in any one structural bay width, and +/-5mm
lines and bed joints overall.
▪ Plumb: +/-2mm of vertical in any one structural bay width, and +/-5mm overall.
= ▪ Plane: +/-2mm of the principle plane in any one storey height or structural bay
width, and +/-5mm overall.
String lines, stretched
between battens Rainscreen cladding systems

Design should allow for the line, level, plumb and plane of the completed
= rainscreen cladding systems to be within the acceptable tolerances of:

▪ Line: +/- 3mm in any one storey height or structural bay width
Rigid vertical battens, ▪ Level: +/- 3mm of horizontal in any one structural bay width
approx 300mm from ▪ Plumb: +/-3 mm of vertical in any one structural bay width,
wall face ▪ Plane: +/- 3mm of the principle plane in any one storey height or structural bay
width.
Stone external leaf
Tile Hanging
Internal leaf The uniform appearance is to be maintained for panels of tile hanging, especially
at abutments. No significant variations in finish or colour should be present.

Timber cladding

Variations in colour to uncoated timbers exposed to weather conditions are to be

expected, the rate and extent of which may vary.

Brick slip cladding

Tolerances for the finish of brick-slip cladding should meet the same as those
listed for fair-faced masonry.

Cast and real stone

▪ Finishes should be reasonably uniform in colour and texture.

▪ Efflorescence, fungal growth, and colour variation may occur due to mitigating
factors such as the orientation of the wall, shading, and even pollution.

© MD Insurance Services Limited 2023 451 Tolerances

20.1.3 TOLERANCES: Internal walls

Introduction Outer corners to internal walls Service ducts (up to 250mm)

▪ The wall must be relatively flat. Maximum deviation of +/-3mm measured Setting out of corners, duct casings (larger than 250mm), and associated framing
using a 2m straight edge is permissible. should be:
▪ The wall must be relatively plumb. Maximum of 8mm from plumb for walls
up to 3m. Taller walls over 3m should be a maximum of 8mm from plumb per ▪ Square. Setting out of corners, duct casings,
storey and no more than 12mm from plumb in their total height. ▪ Neat and tidy. and associated framing should be:
▪ Allowances should be made for minor textural differences around switches ▪ Provided with appropriate decorative finish to their surface.
and such fittings. ▪ Maximum +/- 10mm deviation in 500mm length of surface. ▪ Square.
▪ Board joints should not be readily visible. ▪ Neat and tidy.
▪ Max +/- 3mm surface deviation when measured using a 450mm straight edge. ▪ Provided with appropriate
▪ Viewed from a distance of at least 2m in natural daylight (no artificial lighting decorative finish to their surface.
to be used). ▪ Maximum +/- 5mm deviation
▪ Jointing tape should not be visible within the finished surface. in 250mm length of surface
▪ Some cracking (up to 2mm wide) may occur at wall, floor and ceiling junctions, relating to the boxing of the
due to shrinkage and differential movement of materials. service duct (for lengths of wall
over 250mm please refer to the
requirement for ‘Internal corners
Flatness and plumb of internal walls of internal walls).
+/- 5mm max

Maximum +/- 10mm Internal openings (for reveals) for windows and doors
deviation in 500mm
length of surface. Internal openings must be:
Maximum deviation Maximum of 8mm
of +/-3mm measured from plumb for ▪ Flat along the length of sills and boards with maximum deviation of +/-3mm in
using a 2m straight walls up to 3m. Internal face of wall every 2m.
edge is permissible. ▪ Heads and sill to be level, with a maximum deviations of 3mm out of level for
Taller walls over openings up to 1.5m; where openings are longer than 1.5m then this deviation
3m should be a may be increased to maximum 5mm out of level.
maximum of 8mm ▪ Reveals are to be plumb, with a maximum deviation of +/-3mm for openings
from plumb per up to 1.5m high; where reveals exceed 1.5m high then a maximum deviation
storey and no more of +/-5mm is permissible.
than 12mm from Internal corners of internal walls ▪ Level within +/- 3mm across the depth of the sill, measured from the face of
plumb in their total the frame (tiled sills may be intentionally laid to a fall to allow moisture run-off).
height. Setting out of corners, duct casings, and associated framing should be: ▪ Reveals are to be square with a maximum deviation of +/- 5mm for reveals up
to 250mm deep (deeper reveals should refer to external corners).
▪ Square.
▪ Neat and tidy. Note: Also see the Tolerances for window and door frames.
▪ Provided with appropriate decorative finish to their surface.
▪ Maximum +/-10mm deviation in 500mm length of surface.

Heads and sill to be

level
Maximum +/-
10mm deviation Internal face
in 500mm length of wall
of surface.
Level across the depth
of the sill

Maximum +/-
10mm deviation
Internal face in 500mm length Reveals are to be
of wall of surface. plumb
Frames must be
Internal face of wall plumb

© MD Insurance Services Limited 2023 452 Tolerances

20.1.4 Tolerances: Steel frame and timber frame

Steel frame: wall panel erection tolerances Timber frame: wall panel erection tolerances

+/- 10mm
per storey

+/- 10mm +/- 10mm over full height

per storey of building

Manufacturing tolerances
The following are our manufacturing tolerances that timber frame manufacturers’ must adhere to:

▪ Length: +/-3mm.
▪ Height: +/-2mm.
+/- 5mm +/- 15mm over full height ▪ Diagonals should be equal, acceptable deviation is +/-5mm.
per storey of wall 3 stories or ▪ Opening dimensions: +5mm.
+/- 10mm in overall
height of wall 2 stories Sub structure
It is important that the tight tolerances for timber frame are understood, getting the location and level of the sub-structure
correct is one of the most important parts of the build process. The sub-structure or upstands that support the timber frame
should be set out to the dimensions noted on the timber frame drawings:
Site tolerances
It is essential that the accuracy of setting out foundations and ground beams are checked well in advance of materials being ▪ Within +/-10mm in length, width and line.
delivered to site. ▪ Diagonals should be within +/-5mm up to 10m, and +/-10mm more than 10m.
▪ Levelled to +/-5mm from datum.
For accurate erection of the frame the following tolerances are required at the level of the base of the wall frame:
Location
• Length of wall frame: +/-10mm in 10m. Sole plates should:
• Line of wall frame: +/-5mm from outer face of plate. ▪ Be levelled to +/-5mm from datum.
• Level of base of wall frame: +/-5mm over complete wall line. ▪ Not overhang or be set back from the substructure by more than 12mm on a 89mm sole plate and 20mm for a 140mm
sole plate. .
Metal stud framework ▪ Be set out within +/-10mm in length and in line within +/-5mm, as defined by the timber frame drawings.
The wall panel usually consists of a head rail, base rail (sole plate) and possibly horizontal noggins at mid-height, together ▪ Diagonals should be within +/-5mm up to 10m, and +/-10mm for more than 10m.
with vertical wall studs.
Wall panel erection tolerances
Vertical tolerances are: Wall panels should be erected to the following tolerances:
▪ +/-10mm from plumb per storey height.
▪ +/-15mm in overall height of wall 3 storey or; ▪ +/-10mm from plumb over the full height of the building.
▪ +/-10mm in overall height of wall 2 storey or; ▪ +/-3mm from line of sole plate, with maximum +/-5mm deviation from drawing.
▪ +/-5mm in storey height (approx. 2.5m). ▪ +/-5mm from line at mid height of wall panel.
▪ Inside faces of adjacent wall panels should be flush.
▪ Adjacent wall panels should be tightly butted.
▪ The sole plate and base rail faces should be flush.

© MD Insurance Services Limited 2023 453 Tolerances

20.1.5 TOLERANCES: Internal floors and ceilings

Floors Internal ceilings

Floors levels ▪ The ceiling must be relatively flat. Maximum deviation of +/- 5mm is
The effects of normal drying out / shrinkage of floors (timber and concrete) may permissible using a 2m straight edge with equal offsets.
result in minor differences in level and can result in squeaking of materials as they ▪ Ceilings must be relatively level. Maximum deviation of 3mm per 1m is
move against each other which might not be able to be eliminated entirely. permissible for ceilings up 6m in length.
▪ Ceilings over 6m horizontal length are permitted to have a deviation of 20mm
▪ The floor must be relatively flat. Maximum deviation of +/- 5mm is permissible across their length.
using a 2m straight edge with equal offsets. ▪ Some cracking (up to 2mm wide) may occur at wall, floor and ceiling junctions,
▪ Floors must be relatively level. Maximum deviation of 3mm per 1m is due to shrinkage and differential movement of materials.
permissible for floors up 6m in length.
▪ Floors over 6m horizontal length are permitted to have a maximum deviation
of 20mm across their length.
Level of ceiling
Maximum deviation of 3mm per 1m
is permissible for ceilings up 6m in
length.

Measured between the furthest points

Floors must be relatively

Flatness of ceiling
level. Maximum deviation of
3mm per 1m is permissible Maximum deviation of +/- 5mm
for floors up 6m in length. deviation is permissible using a 2m
straight edge with equal offsets.

Floor deflection limits

The deflection limit must be 0.003 X the span with a maximum deflection of 14mm
where strutting is provided and 12mm where strutting is not provided. This is
based on the total and imposed loads for combined bending and shear.

The Engineer must ensure that the design of the floor construction does not 2m
deflect greater than the above tolerances, unless the relevant BS or EN design
code requires the deflection to be smaller.

© MD Insurance Services Limited 2023 454 Tolerances

20.1.6 TOLERANCES: Window and door frames

Doors Window frames Scratches on doors, windows and frames

All doors should be installed in accordance with the manufacturers’ guidance ▪ Factory-finished door and window components should not have conspicuous
and recommendations. Door installations should adhere to Building Regulatory abrasions or scratches when viewed from a distance of 0.5m.
requirements for Fire & Ventilation. ▪ Surface abrasions caused during the building-in process should be removed
in accordance with the manufacturer’s instructions, which may include
▪ Frames must be plumb within a maximum deviation of +/-5mm over the total polishing out, re-spraying or painting.
height to the frame. Frames must be plumb within a ▪ In rooms where there is no daylight, scratches should be viewed in artificial
▪ Maximum permissible gap between the door and head/jamb is 4mm. maximum deviation of +/-3mm light from fixed wall or ceiling outlets, and not from portable equipment.
▪ Where double doors meet the gap at the stiles should be within 4mm. for window frames up to 1.5 in
▪ Distortion across the faces of the doors should be limited to 5mm in height height. Maximum deviation can
and 3mm in width. be increased to +/- 5mm for
▪ Gaps to the underside of doors will need to take into consideration frames over 1.5m high.
Joint sealants
requirements of applicable Building Regulations. However, the maximum
permissible should be between 10mm and 22mm. Sealants must be tool finished in order to:
Note: These dimensions are without prejudice to satisfactory performance in Frames must be ▪ Remove any blisters and irregularities within the product.
terms of weather tightness, exclusion of draughts and fire resistance where plumb ▪ Achieve a compressed and smooth, neat finish within its surface.
appropriate.

Door frames

Frames must be
plumb
Glazing
Glass must meet the visual assessment criteria of CWCT Technical Note 35
(TN 35). The total number of faults permitted in a glass unit shall be the sum
total of those permitted by the relevant BS EN Standard for each pane of glass
incorporated into the unit concerned.

Acceptable faults include:

Distortion across the
faces of the doors ▪ Bubbles or blisters.
should be limited to ▪ Hairlines or blobs.
5mm in height and ▪ Fine scratches not more than 25mm long.
3mm in width. ▪ Minute particles.

When assessing the appearance of glass:

Maximum permissible ▪ The viewing distance used shall be the furthest stated in any of the BS EN
gap between the door Standards for the glass types incorporated in the glazed unit. In the event
and head/jamb is 4mm. of doubt, the viewing distance shall be 2m (3m for toughened, laminated, or
coated glass).
▪ The viewing shall commence at the viewing distance, and shall not be
preceded by viewing at a closer distance.
▪ The viewing shall be undertaken in normal daylight conditions, without use of
Gaps to the underside of doors magnification.
will need to take into consideration ▪ The above does not apply within 6mm of the edge of the pane, where minor
requirements of applicable scratching is acceptable.
Building Regulations. However,
the maximum permissible should
be between 10mm and 22mm.

© MD Insurance Services Limited 2023 455 Tolerances

20.1.7 TOLERANCES: Finishes and externals

Skirtings Wall tiling Garages

▪ The gap between the floor (without coverings) and the bottom face of the Courses should be straight and even to form a plane and regular surface, Garages shall be constructed to achieve an acceptable appearance. The floors,
skirting should not exceed 5mm at the time of completion. It should be noted especially around fittings and fixtures. walls, and roofs should be built to appropriate tolerances.
that the gap may increase due to normal drying out, shrinkage, or deflection
(particularly to timber floors). ▪ There should be no cut or unfinished tiles at exposed edges or external ▪ Garages are not considered habitable spaces.
▪ It is possible that there will be joints in skirtings on long walls. When viewed corners. ▪ Gaps up to 2mm wide may be experienced in unplastered blockwork. Caused
from a distance of 2m in daylight, joints will need to show a consistent ▪ Joints should be even and cut neatly. by thermal movement and/or shrinkage.
appearance. ▪ Spacing should be sufficient to allow for expansion. ▪ Garage floors may be installed with falls provided in order to either assist with
▪ It is anticipated that there will be some initial shrinkage of the skirting after ▪ Up to sanitary fittings and fixings, the sealing method should be in accordance drainage, or to satisfy the requirements of the Building Regulations.
occupation of the building. with the design and account for movement.
▪ Proprietary water-resistant grouting should be used in accordance with the
manufacturer’s recommendations.
Fitted furniture ▪ Appropriately designed movement joints should be:
▪ Built into tiling at centres at a maximum of 4.5m, vertically and
▪ Fitted furniture with doors and drawers should be aligned vertically, horizontally.
horizontally and in plan. ▪ Provided at vertical corners in large tiled areas.
▪ Factory finished components should not have conspicuous abrasions or ▪ Located at junctions where there are variations in surfaces or
scratches when viewed in daylight from a distance of 0.5m. backgrounds.
▪ Function as designed by the manufacturer. ▪ 1-2mm where tiles are without spacer lugs.
▪ Adjacent doors and/or drawers with any gaps between them should be ▪ Grouting should be:
consistent. ▪ As specified in the design, including mix and colour.
▪ At the intersection of adjacent worktops, there should not be a visible change ▪ Cement-based epoxy resin or a proprietary product.
in level. ▪ Waterproof in and around shower enclosures and where tiling can be
saturated.

Painted and varnished surfaces Radiators and similar appliances

▪ All surfaces should be reasonably smooth as practicably possible when Appliances displayed in and about the home should be:
viewed in daylight from a 2 metre distance and not by shining any artificial
light onto the surface. ▪ Free from cracks, holes, and splits.
▪ Significant nail holes, cracks and splits should not be seen and should be ▪ Have any joints filled consistent to the main material.
filled to reduce their visible appearance. ▪ Reasonably uniform in colour, texture and finish.
▪ Colour, texture and finish should be reasonably consistent and any joints are
to be filled where necessary. Although it should be noted that some variations
can occur. External plastic and UPVC materials (other than windows
▪ External finishes may dull over time depending on a number of factors.
▪ Some seeping of resin from knots is a natural occurrence that may cause and doors)
paintwork discolouration both internally and externally.
Materials such as fascias, soffits, meter boxes, etc. should be provided to meet
the following:
Sanitary ware
▪ Be reasonably smooth in their finish. Free from nail holes, any cracks or splits.
Sanitary fittings should be free from conspicuous abrasions, scratches and chips ▪ All joints to be sympathetically filled to replicate the main material.
when viewed from a distance of 0.5m in general daylight. Where sanitary ware is ▪ Be reasonably uniform in colour, texture, and finish.
provided in windowless accommodation the items should be viewed in artificial
lighting from the fixed wall or ceiling provisions (not from portable equipment).
Pitched roof coverings
Drives and paths Coverings should have an aesthetically suitable appearance.

▪ Surface variation should not exceed +/-10mm from a 2m straight edge with Tiles and slates should:
equal offsets. However, it should be accepted that localised falls into gullies
and channels are acceptable. ▪ Be reasonably uniform, with a consistent texture and finish.
▪ Design and construction should be completed to minimise the potential for ▪ Be selected from mixed packets to avoid excessive colour banding.
standing water. Sixty minutes after rainfall has ceased, areas of temporary
standing water should be no deeper than 5mm, nor exceed 1m2 in area. It should also be accepted that:
Temporary standing water should not be present adjacent to entrance doors.
▪ Some fracturing or weathering may also appear if using natural stone due to ▪ Some minor blemishes can occur within the surfaces of the tile or slate.
the make-up of the material. This tolerance applies to principle pathways and ▪ Variations in colour, texture, and finish can occur within tiles and slates,
driveways to the building that are required to meet the standards of Part M especially when natural quarried items.
(Access to and use of buildings). ▪ Efflorescence is to be expected.

Drainage system covers

▪ Drainage system covers in hard standing areas should line up neatly with the
adjacent ground.

© MD Insurance Services Limited 2023 456 Tolerances

T 0800 183 1755 E enquiries@labcwarranty.co.uk labcwarranty.co.uk

@LABC_Warranty LABC Warranty LABC Warranty

MD Insurance Services Ltd. is the scheme administrator for LABC Warranty and is authorised and regulated by the Financial Conduct Authority. Registered in England No: 3642459. TS-11A-11.00-010223