At a glance
| Clause | State exactly | If left loose, a tenderer can | Close it with |
|---|---|---|---|
| 1 Scope and drawings | Drawing numbers and revisions; what is in or out; who surveys. | Price an old revision, omit items, assume someone else surveys. | A drawing schedule with revision letters. |
| 2 Species | Botanical and common name; origin if it matters. | Offer a cheaper species or origin that fits the common name. | A labelled sample board. |
| 3 Cut | Through-and-through, plain, quarter or rift sawn. | Choose the cut that yields most from the log. | A control sample showing the cut. |
| 4 Grade and appearance | Allowed knots, sapwood, colour range and grain direction. | Include features the design never intended. | An approved sample and a written limit per feature. |
| 5 Finished sizes | Finished, not nominal, thicknesses and widths. | Price nominal sizes that plane down smaller. | “Finished size” on every drawing. |
| 6 Moisture and movement | Moisture content at dispatch and the room it must suit. | Use timber that keeps moving after fitting. | A recorded reading at dispatch. |
| 7 Board type and grade | Family, standard, grade, thickness, balancing, fire class. | Use a lower grade, a thinner board or no balancing. | The board datasheet or declaration of performance. |
| 8 Veneer and match | Species, cut, grade, thickness, match, sequence, backing. | Use a plainer cut, a random match or a thinner leaf. | An approved veneer sample and layout drawing. |
| 9 Edges and construction | Edge, carcase joint, drawer box, back panel. | Pick the cheapest edge, joint or box that holds. | A construction sample or detail drawing. |
| 10 Hardware | Reference, type, size, finish, quantity, load rating. | Fit a lighter fitting “to suit”. | A hardware sample and its data sheet. |
| 11 Finish and sheen | System, coats, sheen, colour reference, all faces. | Cut the coats, change the system, skip the insides. | A finish sample on the same species and cut. |
| 12 Certificates and evidence | Timber claim, fire or emission evidence, handover documents. | Quote without the paperwork, then charge it as an extra. | A certificate number checked against the delivery note. |
Numbers match the markers on the drawing. Square brackets in the wording are example values to replace.
Twelve clauses on one piece of joinery
Every clause in the table has a place on the piece. The timber top and the stiles carry the species, the cut and the grade. The panels carry the veneer and the match, the carcase carries the board, the drawer carries the construction, and the hinges carry the hardware. The finish runs over all of it, and the certificates sit behind it.
Read the table the other way round and it becomes a test. If someone who has not seen the design can name the species, the cut, the board, the finish and the hinge from your specification alone, the specification is closed. Where they hesitate, a tenderer will fill the gap, and not always the way you would.
What a vague line allows, and the line that closes it
Nobody here is doing anything wrong. A loose line is an invitation to use judgement, and judgement under price pressure goes the cheap way. The remedy is not a longer specification, it is one reading per line. Ten of the lines that most often stay open:
| The loose line | What a tenderer can still price | The closed line |
|---|---|---|
| “Oak” | Any oak species or origin, any cut, any grade, sapwood and mixed grain included. | European oak (Quercus robur or Q. petraea), quarter sawn, appearance as control sample S-01. |
| “Oak veneered doors” | Any leaf thickness, cut and match, on any board, with no balancing layer behind. | Oak veneer, quarter cut, book matched and sequence matched across the run, on [board], balanced on the reverse. |
| “Painted finish” | Any system and number of coats, any sheen, insides left unfinished. | [System] in [n] coats over [primer], colour [reference], sheen as sample S-02, all faces including insides. |
| “25 mm thick” | A nominal 25 mm board that planes to something thinner. | 25 mm finished thickness. |
| “Soft-close drawers” | Any runner, any box material, any joint. | Drawer box [material, thickness, joint] on [runner type and reference], rated for [load], soft-close. |
| “Quality hinges to suit” | Any hinge, any number per door. | [n] [type and reference] hinges per door, [finish], rated for a door of [weight]. |
| “Brass handles” | Solid or plated brass, any section, any finish. | [Reference], solid brass, [finish], [length] centre to centre. |
| “FSC timber” | No claim type and no certificate: the word is quoted, the paperwork is not. | [FSC 100% / FSC Mix / PEFC] claim on named items, with the supplier’s certificate number on the delivery note. |
| “To match sample” | A sample nobody has named, signed or kept, judged afterwards. | To match control sample S-01, signed and dated, held by [party]. |
| “Or equivalent” | A cheaper product priced in, with no named test of what counts as equivalent. | No substitution without written approval before the tender return date. |
Tip: if a line contains a word that could describe two different products, it is not yet a specification.
Sample references fix what words cannot
Wording describes, a sample decides. Give every sample a reference, say what it fixes, and say who holds it. The reference then goes into the specification (“to match S-01”) so the sample and the clause cannot drift apart. The timing of samples is agreed project by project, usually once the scope and the quotation are settled.
| Reference | What it fixes | Rule |
|---|---|---|
| S-01 Timber control sample | Species, cut, colour and grain range. | Labelled with botanical name and cut; signed and dated; one copy kept by each party. |
| S-02 Finish sample | System, sheen, colour and how the finish sits on the grain. | Made on the same species and cut as the production; a sample on another board proves little. |
| S-03 Veneer layout and flitch sample | Match, sequence and character of the figure. | A layout drawing and a leaf from the approved flitch, approved before pressing. |
| S-04 Construction sample | Edge, joint, drawer box and back. | A cut-through or a small assembly showing what is actually built. |
| S-05 Hardware sample | Fitting, size, finish and action. | The fitting itself, with its data sheet attached. |
View finish and veneer samples in the light the room will have. Two colours that match in one light can differ in another, so a sample approved at a desk can look wrong on site.
Drawings, substitutions and changes
Decide what you prescribe and what you describe. A prescriptive specification states exactly what is required and the design team keeps the design responsibility. A descriptive one states the result and leaves the specialist to work out how. NBS notes that under a descriptive approach design responsibility lies with the contractor, which may pass to a specialist subcontractor, and that the choice should be made at the outset. For a bespoke piece, say line by line which one you mean.
Ask for shop drawings, and say who approves them. NBS observes that supplier drawings are in many cases not issued back for comment. Write the approval step into the specification, so that production does not start on a drawing nobody has signed.
Control substitutions. “Or equivalent” is not wrong, but it needs a gate: the alternative is offered separately, with its data sheet and a sample, and approved in writing before the tender is returned.
Treat tolerances as their own clause. Manufacturing tolerances and site tolerances are different things. Agree both with the workshop before the tender, and do not quote a figure from a general guide.
Change by written variation. A change after approval states its effect on price and programme before anyone acts on it.
Certification: what to ask for on timber
“FSC timber” is not a claim. FSC UK’s buyer guidance asks you to request certified products at the point of purchase and to make sure the claim appears on the sales documents. Its checklist for delivery paperwork looks for six things: the document date, supplier and customer details, a product description, the quantity delivered, the supplier’s certificate code and the FSC claim itself. The claim types are FSC 100%, FSC Mix and FSC Recycled, each with its own meaning. Specify which one you want, for which items, and check the certificate number against FSC’s database.
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.
Applies to the joinery on drawings [numbers], revision [letter]. Dimensions verified on site by [party] before production. All sizes finished unless marked nominal. Shop drawings and samples [S-01 to S-05] approved before production. No substitution without written approval from [designer] before tender return; any alternative offered separately with its data sheet and a sample. Changes after approval by written variation (price and programme).
Species [European oak (Quercus robur or Q. petraea)], cut [quarter sawn], appearance to match control sample [S-01]; sapwood [not permitted on visible faces]; knots [none on visible faces]. Moisture content [ ]% at dispatch, [heated] interior. Certification [FSC 100% / FSC Mix / PEFC] on [named items]; certificate number and claim on the delivery note.
Boards: [type, standard, grade], [18] mm finished, [fire or emission class]; datasheet or declaration of performance for each. Veneered panels balanced on the reverse. Veneer: [species], [cut], [grade], [thickness] mm, [book matched, sequence matched from one flitch across the run]; layout drawing and flitch leaf approved before pressing [S-03].
Edges [solid lipping / veneered] as sample [S-04]. Carcase joint [type]. Drawer boxes [material, thickness, joint] on [runner type and reference], [load] rated, soft-close. Hinges: [number] per door, [type and reference], [finish], for [weight] doors. Handles [reference, material, finish], [length] centres. Match sample [S-05].
[System] on [species and cut], [number] coats over [primer or grain filler], to all faces including insides, edges and backs. Sheen and colour [reference] to match finish sample [S-02], made on the same species and cut. [Performance test and class where required.] Samples viewed in [the lighting conditions of the room].
Terms used on this page
- Prescriptive specification
- States exactly what products, materials and workmanship are required. Design responsibility stays with the design team.
- Descriptive specification
- States the result required and leaves a specialist or contractor to design how. Design responsibility generally passes with it.
- Nominal size
- The size timber is sold as before planing. The finished size is smaller, by an amount that varies by supplier.
- Control sample
- The approved sample the maker keeps as the benchmark for production, labelled, dated and signed.
Standards and sources
- NBS: RIBA Plan of Work 2020 and specification: prescriptive and descriptive specification (page read 5 Nov 2026).
- FSC UK: Choose FSC and Is it FSC? buyer guides: delivery-document checks and claim types (page dated 7 Jul 2026).
- BS EN 942:2007 Timber in joinery. General requirements: appearance classification (BSI listing read; standard not read).
- BS EN 1313-2:1999 Sawn timber, permitted deviations and sizes (hardwood): BSI listing read; values not read.
- BS EN 622-5:2009 Fibreboards. Requirements for dry process boards (MDF): BSI listing read; standard not read.
- Make Bespoke Studio journal: How to specify bespoke joinery: the longer guide to briefing a package.
Questions we are asked
What should a joinery specification include?
At minimum: the drawings and revision, the timber species and cut, the permitted grade and appearance, finished sizes, the board and veneer, the construction, the hardware with references, the finish system and sheen, and the certificates required. Fix each with a sample reference so the words and the sample agree.
Why is specifying the cut of timber as well as the species important?
Two boards of the same species can look quite different depending on how the log was sawn. Plain sawn, quarter sawn and rift sawn timber show different grain, so naming only the species leaves the look to the tenderer.
What does “or equivalent” allow in a specification?
It allows a tenderer to price a different product from the one named. It is workable if the alternative must be offered separately, with a data sheet and a sample, and approved in writing before the tender is returned.
What is the difference between a prescriptive and a descriptive specification?
A prescriptive specification states exactly what is required and the design team keeps the design responsibility. A descriptive specification states the result and leaves a specialist to decide how, and design responsibility generally follows. NBS recommends deciding which approach to use at the outset.
What should I ask for to prove timber is FSC certified?
Specify the claim type and the items it applies to, then check that the delivery and sales documents show the supplier’s certificate code and the FSC claim. Check the certificate code against FSC’s database.
Download the factsheet
A two-page A4 PDF with the twelve-clause checklist, the marked-up drawing and the paste-in specification wording, to keep with your project file.