At a glance
| Element | Limit in LABC Warranty Technical Manual v11 (2022) | What to allow on the drawing (our note) |
|---|---|---|
| Wall, flatness | ±3 mm, 2 m straight edge with equal offsets. | Plan scribe margins. Never assume a flat wall. |
| Wall, plumb | 8 mm for a wall up to 3 m high. Above 3 m: 8 mm per storey and 12 mm in all. | A 2.4 m unit against a wall at the limit has up to 6.4 mm of lean to scribe off (8 × 2.4 ÷ 3.0); two walls leaning out, 12.8 mm. |
| Corners and openings | Corners ±10 mm in 500 mm. Reveals plumb ±3 mm (±5 mm over 1.5 m). Sills and heads level to 3 mm (5 mm over 1.5 m). | Measure both diagonals, and every opening at three points. |
| Floors and ceilings | Flat ±5 mm over 2 m. Level to 3 mm per metre up to 6 m, and 20 mm over longer runs. | A 3 m run can stand on a floor up to 9 mm out of level (3 × 3): adjustable feet, scribed kick and top strip. |
| Skirting to floor | Gap not over 5 mm at completion; it can grow as the floor dries. | Scribe skirting and plinths to the floor. |
| Door to frame (not fire doors) | Gap at head and jamb 4 mm. Face distortion 5 mm in height, 3 mm in width. | Without prejudice to fire resistance, says the manual. Do not apply to fire doorsets. |
| Fitted furniture | Aligned vertically, horizontally and in plan; gaps consistent; no step at worktop joins. No figure given. | Write your own alignment and gap tolerance. |
These are the limits a new-home warranty scheme treats as acceptable, not design tolerances and not a standard. Our notes and arithmetic are in the third column. A contract or a designer may require tighter figures, and later editions of the manual may differ.
Who says what, and why the numbers move
A tolerance is a number agreed for a job, not a property of a wall. The numbers in circulation come from warranty schemes and trade bodies, and they change. The same warranty provider allowed ±5 mm on a 2 m straight edge for an internal wall in Version 10 of its technical manual and ±3 mm in Version 11. NHBC Standards and the Premier Guarantee manual publish limits of their own which we could not read, so we do not quote them.
We looked for a British Standard that gives allowances between joinery and the building. BS 8000-5 is the code of practice for site carpentry and joinery, but the BSI listing does not mention tolerances and we have not read the standard. BS 5606, the guide to accuracy in building, is listed by BSI as withdrawn in 2022. So the honest position is that no UK standard we could read tells a designer how much scribe to allow. Write the number you measured.
| Source | Wall flatness | Wall plumb | Floors | Status |
|---|---|---|---|---|
| LABC Warranty Technical Manual, Version 11, Section 20 (pp. 452 to 456; dated December 2022) | ±3 mm, 2 m straight edge | 8 mm to 3 m; 12 mm in all above 3 m | Flat ±5 mm over 2 m; level 3 mm per metre to 6 m | Read |
| LABC Warranty Technical Manual, Version 10, Section 1 | ±5 mm, 2 m straight edge; no sharp step over 4 mm in 300 mm | 10 mm in a storey up to 2.5 m; 20 mm above | Not compared | Read |
| Architectural Woodwork Standards, 1st edition (2009), US | Over 6.4 mm in 3,658 mm is not acceptable for installing woodwork | Same | Over 12.7 mm in 3,658 mm is not acceptable | Read (US practice; the 3,658 mm is 144 inches) |
| BS 8000-5:1990, carpentry, joinery and general fixings | Not read | Not read | Not read | BSI listing only; its abstract does not mention tolerances |
| NHBC Standards; Premier Guarantee manual | Each publishes its own limits | Not read: NHBC needs a login, the Premier Guarantee page was not retrievable |
The only source we read that speaks directly to joinery installation is the US Architectural Woodwork Standards: wall, ceiling and opening variations of more than 6.4 mm, or floor variations of more than 12.7 mm, in 3,658 mm are not acceptable for installing woodwork, and it is not the installer’s responsibility to scribe or fit to tolerances beyond them. It is a US standard, and we show it for comparison only.
Scribing, and how much to allow
To scribe is to shape the edge of a panel or board so that it follows an uneven wall, floor or ceiling. A scribe strip is a deliberately oversized piece, cut to fit. The drawing shows a unit in an alcove where the walls, floor and ceiling are all a little out. The unit itself is square and level; the green strips are cut to the wall, the ceiling and the floor, and the plinth stands on adjustable feet and is scribed to the floor. A shadow gap, a deliberate recessed gap at a junction, is the other way of letting a straight edge meet an uneven one.
Work the allowance from the survey. The method is arithmetic, and the example below uses the numbers in the drawing.
| Step | Example (mm) |
|---|---|
| Measure the opening width at three heights and three depths. | Narrowest 2,940, widest 2,958. |
| Choose the carcass width from the narrowest reading, leaving room to scribe. | Carcass 2,890. |
| Work out the margin each side at the narrowest and at the widest point. | (2,940 − 2,890) ÷ 2 = 25; (2,958 − 2,890) ÷ 2 = 34. |
| Make each scribe strip wider than the largest margin, plus material to cut away. | [34] plus [10] to cut = a [44] mm strip. |
The result is a margin that changes along the run, wider where the opening is wider. No standard we read fixes a scribe width. The US standard mentions two numbers for its own cabinet series: scribes at wall-to-wall installations not wider than 38.1 mm, and shimming of a toe base up to 12.7 mm, which it treats as acceptable. We quote them only to show the order of magnitude, not as a rule.
Survey before the drawings are fixed
- Survey when the walls are finished. Measure after plaster or drylining is complete, so that the numbers are those the joinery will meet. Our wall panelling guide says the same: book the survey once the walls are built and plastered.
- Width at three heights, height at three places. For each opening or run, measure the width at floor, mid-height and top, and the height at left, middle and right. One reading hides a leaning wall.
- Plumb and square. Check each wall for plumb with a level or a laser, and measure both diagonals of the opening to see how far it is from square.
- Floor and ceiling to one datum. Take levels at several points against a single level datum, so that the plinth range and the top scribe can be drawn.
- Services and projections. Mark sockets, switches, pipes, radiators, sills, bars of existing skirting and anything that sticks out. The joinery has to go round them.
- Tape or laser. A tape is enough for a small alcove. For a long run or a room of several walls a laser survey gives one set of readings to a single datum.
- Record it on a drawing. Put the readings, the datum and the date on a survey drawing, photograph the site, and have the designer sign it off before production.
Who corrects what
Responsibility is set by the contract, so write it down. The table shows how the US standard divides it and how it usually runs on a UK job. It is general practice, not legal advice.
| Item | Usually with | Write it in |
|---|---|---|
| Walls, floors and ceilings built within the agreed limits | The main contractor and its plasterer or drylining subcontractor. | The main contract, and the assumed limits in the joinery specification. |
| Backing, blocking and grounds in the wall for fixing joinery | The main contractor. The US standard says these are not furnished or installed by the woodwork installer. | The fixing schedule on the drawings. |
| Survey of openings and dimensions | Agree it: the workshop, or the contractor with the workshop checking. | The scope of the joinery package. |
| Scribing joinery to walls, floor and ceiling within the limits | The joinery installer. | The specification: scribe allowances and who fits. |
| Correcting a wall or floor outside the limits | The main contractor, before joinery goes in. The US standard says the installer need not scribe past its limits, and floors beyond 12.7 mm are corrected before cabinets are installed. | A written variation if it is found after the joinery is made. |
| Fire doorsets | Fitted to the certified installation instructions for that door. | The door schedule and the fire strategy. |
What to put on the drawing and in the specification
- Show the scribe. Draw scribe strips, fillers and the shadow gap where the joinery meets the building, with the margin in millimetres, so that the workshop cuts material for it.
- Say finished or nominal. State that sizes are finished, and that the unit sizes are confirmed after the survey.
- Give the plinth a range. State the range the feet adjust through and the datum they are set from, measured from finished floor level.
- State the limits you assume. Say what the walls, floors and ceilings are assumed to be within, and what happens where the survey finds more: the contractor corrects it, or a variation is raised before production.
- Fire doors are different. A fire doorset is fitted to the installation instructions that come with its test evidence. Do not scribe or plane a fire door to suit the opening.
The specification checklist puts tolerances in a clause of their own, and skirting and architrave sizes deals with the junction at the floor.
Specification wording
Paste into your schedule or specification and replace anything in [square brackets] with your own figures. Wording is a starting point: your specification governs.
Dimensions to be verified on site by [party] before shop drawings. The survey to record, for each opening or run, the width at [three] heights, the height at [three] positions, the plumb of each wall, floor and ceiling levels to a single datum, and the position of services. Survey drawing [number] to be signed off by [designer] before production.
Joinery against walls, floors and ceilings to be scribed. Scribe margin of [25] mm at each end of each run, shown on the drawings and confirmed by survey. Walls, floors and ceilings are assumed to be within [3] mm of flat on a 2 m straight edge and [8] mm of plumb in [3] m. Where the survey shows more, [the main contractor is to correct it / a variation is to be raised] before production.
Plinths on [adjustable feet], range [ ] mm, set from a single level datum at [ ] mm above finished floor level, and scribed to the floor. Floor finish to be in place [before / after] fitting.
Shadow gaps [ ] mm, even to [ ] mm, as drawing [number]. Door and drawer margins [ ] mm and consistent; doors and drawers aligned vertically, horizontally and in plan. [Fire doorsets to be fitted to the certified installation instructions; the leaf is not to be scribed or planed.]
Terms used on this page
- Scribe
- To shape the edge of a panel or board so it follows an uneven wall, floor or ceiling; a scribe strip is a deliberately oversized piece cut to fit.
- Shadow gap
- A deliberate recessed gap, usually 6-12 mm, at a junction such as skirting to wall, that hides the irregularities of the wall and reads as a clean dark line.
- Plinth
- The recessed base under a run of cabinets or a wardrobe, which gives toe space and lets the floor be scribed against it.
- Datum
- The single reference level or line that all heights on a drawing and a survey are measured from.
- Plumb
- Truly vertical. A wall out of plumb leans.
- Straight edge
- A long rigid rule, commonly 2 m, laid on a surface to measure how far it departs from flat.
Standards and sources
- LABC Warranty Technical Manual Version 11, Section 20 Tolerances (pp. 448 to 456; (c) MD Insurance Services Limited 2023): 20.1.3 walls, 20.1.5 floors and ceilings, 20.1.6 frames, 20.1.7 skirtings and fitted furniture. Read 5 Nov 2026.
- LABC Warranty Technical Manual Version 10, Section 1 Tolerances: walls and ceilings. Read 5 Nov 2026.
- Architectural Woodwork Standards, 1st edition (2009), Section 10 Casework: 1.2.9, 1.2.20.1.4, 1.5.1, 1.5.2. US practice.
- BS 8000-5:1990 Workmanship on building sites. Carpentry, joinery and general fixings: BSI listing only; not read.
- BS 5606:1990 Guide to accuracy in building: BSI listing: withdrawn 23 Feb 2022; not read.
Questions we are asked
What tolerances can I expect on site for fitted joinery?
Workshop joinery is made far tighter than a building is built, so the allowance goes in the scribe, not in the carcass. We found no UK standard we could read that sets joinery-to-wall tolerances. One new-home warranty scheme (LABC Warranty, Version 11) treats an internal wall as acceptable if it is flat to within 3 mm on a 2 m straight edge and no more than 8 mm out of plumb up to 3 m high. Survey the real opening instead of relying on a figure.
How much scribe allowance should a drawing include?
No standard we read fixes it. Work it from the survey: subtract the carcass width from the narrowest reading of the opening and share the difference between the two ends, then make the scribe strip wider than the largest margin plus material to cut away. The worked example on this page gives 25 mm each side at the narrowest point and up to 34 mm where the opening is wider.
How out of plumb can a wall be before it has to be corrected?
It depends on the contract. LABC Warranty Version 11 allows 8 mm from plumb for a wall up to 3 m high and treats more as outside its limits, but that is a warranty acceptance level for new homes, not a design tolerance. Your specification, or the main contract, sets what the contractor has to deliver, and the joinery should assume nothing better than what the survey shows.
Who is responsible for walls that are out of true, the joiner or the contractor?
The contract decides. The US woodwork standards say that backing and blocking are not the installer’s job, that the installer need not scribe past 6.4 mm in 3,658 mm on a wall or 12.7 mm on a floor, and that floors beyond that are corrected before cabinets go in. On a UK job the usual arrangement is that the main contractor builds to the agreed limits and the joiner scribes within them: write it down.
What is the difference between a scribe strip and a shadow gap?
A scribe strip is a deliberately oversized strip cut to follow an uneven wall, floor or ceiling so that the joinery meets it with no visible gap. A shadow gap is a deliberate recessed gap at a junction, which lets a straight edge sit beside an uneven one and reads as a clean dark line. Both are detailed on the drawing.
Download the factsheet
A two-page A4 PDF with the limits, the dimensioned alcove drawing, the scribe allowance worked through and paste-in wording for the survey, scribing and plinth, to keep with your project file.