How to specify internal doors

How do you specify internal doors?

To specify internal doors, specify a factory-made timber doorset rather than a loose leaf and frame: state the leaf construction and thickness, facing and lipping, frame profile, duty class to BS EN 1192, clear opening width, glazing and any acoustic seals. Confirm with the fire strategy that each door really is a non-fire door, then let the door schedule give each opening its type, size, handing and ironmongery set.

The doors that are not fire doors get the least attention in most specifications. They are often covered by one line, "internal doors to be hardwood-lipped flush doors in softwood frames", with everything else left to the joinery supplier. That line does not say how heavy the leaf is, so nobody can check the hinges. It does not give a clear width, so the accessible WC door is sized from the leaf. It says nothing about the gap at the bottom, which is where ventilation and acoustic requirements meet.

This guide covers internal timber doorsets under Uniclass Pr_30_59_24_97 Wood doorsets, for offices, schools, housing and healthcare where the door has no fire rating. Fire-resisting doorsets use the same code but bring their own certification rules, which are covered in how to specify fire doors. Where leaf and frame are bought separately, the leaf has its own codes, Pr_30_59_23_97 Wood flush door leaves and Pr_30_59_23_98 Wood panelled door leaves.

What does a internal door clause need to cover?

Some properties are specific to internal doors. Others belong in every product clause. A clause that leaves either out gives the contractor room to substitute.

Fields marked Never guess depend on the project and should never be filled from a default or a previous job. If the information is not available yet, the clause should say so with a TBC and a reason.

Which decisions does the clause depend on?

Most properties follow from the product you choose. These depend on the project, so they need a decision from the designer before the clause is written.

Which standards should the clause cite?

Cite the product standard the declaration of performance refers to, the code of practice for installation, and the test method behind each value you set. A value without its test method cannot be checked against a submittal.

BS EN 14351-2

Windows and doors. Product standard, performance characteristics. Internal pedestrian doorsets

The European product standard for internal pedestrian doorsets, excluding fire resistance and smoke control. It lists the characteristics a maker can declare, such as acoustic performance, mechanical strength and operating forces.

In the clause Cite it where the maker declares to it, and ask for the test report behind each property: "Doorset to BS EN 14351-2, declared performance to be submitted".

BS 4787-1

Internal and external wood doorsets, door leaves and frames. Specification for dimensional requirements

UK coordinating sizes for wood doorsets, leaves and frames. Still current, and the source of the familiar 2040 mm height and metric leaf widths.

In the clause Use it when the leaves are standard sizes: "Leaf sizes: To BS 4787-1, as door schedule".

BS EN 1192

Doors. Classification of strength requirements

Classes 1 to 4 (light, medium, heavy and severe duty) for resistance to vertical load, torsion and impact.

In the clause "Strength: Class 3 (heavy duty) to BS EN 1192."

BS EN 942

Timber in joinery. General requirements

Appearance classes (J2 to J50) for timber in joinery, and moisture content at delivery.

In the clause "Frames: Hardwood to BS EN 942, appearance class J10 for clear finish."

BS EN 12600

Glass in building. Pendulum test. Impact test method and classification for flat glass

The impact classes, such as 1(B)1 and 2(B)2, used to show glass is safe in critical locations.

In the clause "Glazing: Class 2(B)2 to BS EN 12600."

BS 8300-2

Design of an accessible and inclusive built environment. Buildings. Code of practice

Guidance on door widths, vision panels, ironmongery, visual contrast and opening forces, in more detail than Approved Document M.

In the clause "Door leaf and frame to contrast visually with the surrounding wall, as BS 8300-2."

BS EN 13501-1

Fire classification of construction products and building elements. Classification using data from reaction to fire tests

The Euroclass system for surfaces, used where the fire strategy sets a reaction to fire class for doors on escape routes.

In the clause "Reaction to fire: Class B-s3,d2 to BS EN 13501-1, where scheduled."

Confirm the current edition of each standard at every issue. Avoice's State of UK Specifications 2026 found a withdrawn standard cited in 40% of specifications at contract issue.

For the regulations behind these choices, see Approved Document M explained, Approved Document K explained, or search the Avoice Regulations library.

How do you write it in CAWS?

In CAWS, internal doorsets are written in L20 as product clauses in the 400s, one for each door type on the door schedule. A wood doorset clause covers the leaf (core, thickness, facings, lippings, finish), the frame and architraves, glazing and beads, ironmongery reference, seals, strength and any acoustic or access requirements. The door schedule then gives each door its type, size and handing.

L20 also has a general clause for non-fire-resisting doors, which sits beside the fire door clause, and execution clauses for fixing doorsets, fixing wood frames, fitting ironmongery and hinge positions. A project with veneered meeting room doors and paint-grade office doors has two type clauses sharing those general clauses.

Clauses the type clause relies on

L20/110

Evidence of performance Test reports and data for strength, acoustic and glazing claims, submitted before ordering.

L20/120

Non-fire-resisting pedestrian doors/ door assemblies/ doorsets General requirement for certified evidence that doors with no fire rating meet the specified performance.

L20/170

Control samples A finished sample door and frame approved before the order is placed.

L20/750

Fixing doorsets Fixing the complete doorset plumb, square and to the maker's instructions.

L20/830

Fixing ironmongery generally Cutting in and fixing hardware without weakening the leaf.

L20/850

Location of hinges Hinge positions and number per leaf.

Clause numbers vary between NBS versions and practice masters. These follow the L20 section of a published NBS-format refurbishment specification; check that each clause your type clause refers to exists in your own L20.

How do you write it in Uniclass?

In Uniclass the door in its opening is a system and the doorset is a product. For a hinged internal door the system is Ss_25_30_20_39 Hinged doorset systems. It describes the doorset in the wall: how it is fixed, the finished floor and undercut, the ironmongery set, and what the installed door must achieve for access and sound.

The doorset itself is a product clause under Pr_30_59_24_97 Wood doorsets, holding leaf construction, facings, lippings, frame, glazing and strength class. Write two product clauses if the project has two leaf types, and point each hinged doorset system at the right one. Fire doors go under the same Pr code but in their own product clauses, so a change to the plain doors never touches the certified ones.

In NBS Chorus, Uniclass product clauses also carry an NBS reference (for wood doorsets, 45-25-28/348); keep CAWS and Uniclass references out of the same specification.

What goes in the spec, and what goes in the schedule?

The specification defines each type once. The schedule and drawings say where each type goes.

For coordination between these documents, see Why your window and door schedules don’t match your specification.

What are the common mistakes?

Most problems are a missing property, a property filled with the wrong kind of value, or a decision left silently open.

• !
  Leaf width in place of clear width. The accessible WC door is drawn at 926 mm and assumed compliant. Once the stop, leaf thickness and lever handle are deducted it may fall short. Schedule the clear width and ask for the calculation.
• !
  "Solid core" with nothing behind it. Particleboard, timber strip and tubular cores are all sold as solid or semi-solid. Tie the core to a BS EN 1192 duty class and to the maker's test evidence.
• !
  Hinges picked before the leaf is known. A heavy veneered acoustic leaf on standard hinges drops within a year. Give the leaf weight to the ironmonger, or require hinges graded for it.
• !
  Undercut measured from the screed. If the floor finish goes down after the doors are hung, a 10 mm undercut becomes 2 mm. Say the undercut is measured from the finished floor.
• !
  Frames ordered before the walls are built. Partition thickness changes with the lining and the acoustic build-up. Fix the frame depth to the wall type, or ask for adjustable frames, before ordering.
• !
  Two descriptions of the same door. The door schedule says "glazed" while the clause says "solid". Keep vision panels on the schedule only and let the clause give the glass class.

How Avoice helps

Avoice drafts internal doorset clauses from your door schedule and plans, and shows which doors it could not resolve.

1. 1
   Drafts from the door schedule

   It reads door types, leaf sizes and ironmongery sets from your door schedule, writes the L20 or Uniclass clause for each type, and fills in the leaf, frame and glazing lines your information supports.

2. 2
   Leaves a TBC where a choice is open

   If the client has not chosen between veneer and paint grade, or the acoustic consultant has not given an Rw for the meeting rooms, the clause says TBC with the reason. Every TBC goes into one project register to close before tender.

3. 3
   Writes in your format

   CAWS L20 type clauses or Uniclass hinged doorset systems with Pr product clauses, adapted from your practice's own master clauses.

4. 4
   Checks doors against the drawings

   QA/QC flags a D12 on the plans with no clause, a plain doorset on a door the fire strategy marks as FD30, a reference to an L20 clause your master does not contain, or a withdrawn standard.

5. 5
   Keeps the evidence with the clause

   Doorset data sheets and test reports sit in the Product Room, linked to the clause. Edit the linked doorset once and every door type that uses it updates. Approved Documents K and M are in the Avoice Regulations library for checking glazing and widths.

Related guides: How to specify fire doors, How to specify door hinges, How to specify door handles.

Software can draft and check. The designer still chooses the product and is responsible for the specification.