Architrave: Sizes, Profiles and Fitting
Architrave frames a door or window opening and covers the joint between the lining and the plaster. Here is how to pick the width, profile and material, how to set the reveal, and how much you actually need per doorway.
By the Calculate My Reno Team / Published
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Architrave is the moulding that frames a door or window opening. It covers the joint between the door lining and the plaster, and that joint is one that always opens: the lining is timber fixed to studwork, the wall around it is plaster, and the two move at different rates for the first couple of years. Architrave hides the gap permanently instead of you filling it every time the house dries out.
It is also the piece that finishes the trim in a room. The skirting runs into it, and if the two are chosen separately you find out at the last minute that they do not meet properly.
What width of architrave
These are the sections most British merchants carry. Ranges vary between suppliers, so check what yours actually stocks before settling on a size, especially in the wider period patterns:
| Width | Where it usually suits |
|---|---|
| 44 - 57 mm | Tight reveals, cupboard doors, and openings close to a corner where a wide section would not fit |
| 69 mm | The common modern default, and the usual partner to 119 mm and 144 mm skirting |
| 95 mm | Larger rooms and taller doors; the usual partner to 169 mm skirting |
| 119 mm and above | Victorian and Edwardian rooms, generally in a deeper moulded pattern |
The proportion that matters is between the architrave and the skirting, not between the architrave and the door. A 69 mm architrave under a 219 mm Victorian skirting looks thin, and a 119 mm architrave in a room with 95 mm skirting crowds the doorway.
Check the space beside the opening before you buy. A door set close to a corner or to a window reveal may not have room for the width you want on both sides, and a lopsided pair of legs is worse than a narrower section used consistently.
Thickness is not a free choice
Architrave is commonly sold in 15 mm, 18 mm, 20 mm and 25 mm thicknesses, and this is the one dimension where taste does not come into it.
The skirting board runs horizontally into the side of the architrave. The architrave has to be as thick as the skirting, or slightly thicker. Get it the other way round and the skirting stands proud of the architrave, leaving a small step at the bottom of the door casing that no amount of filler makes look deliberate.
Where the two come out the same thickness, the traditional answer is a plinth block: a deeper, thicker block at the foot of the architrave that both the architrave and the skirting die into. It also takes the knocks at the one place trim always gets damaged.
The profiles
Architrave is moulded in the same profile families as skirting, and merchants sell them as matching ranges for that reason:
| Profile | What it looks like |
|---|---|
| Torus | A deep rounded convex bead above a step. The most common British profile, and the usual match to torus skirting |
| Ogee | An S-shaped curve, concave into convex. Slightly more decorative than torus |
| Chamfered and rounded | A flat angled cut with a small rounded corner. Plain and contemporary |
| Bullnose | A single rounded-over edge. The plainest of the curved profiles |
| Square edge | No moulding at all. Very modern, and the easiest to cut and fit |
| Lambs tongue / Victorian | Deeper, more elaborate mouldings for period rooms |
Match the architrave profile to the skirting profile, or deliberately pair a moulded skirting with a plain square-edge architrave. What reads as a mistake is two different mouldings meeting at the foot of the door.
The more elaborate the moulding, the more a slightly open mitre shows. On a complicated profile in a house with out-of-square linings, corner blocks are a legitimate way out rather than a compromise.
MDF, softwood or hardwood
MDF is what most of the market buys for painted architrave. It is stable, has no knots or grain to bleed through the paint, comes pre-primed, and takes a crisp mitre. Its weakness is water, so it is a poor choice in a bathroom or utility room, and worth avoiding on a back door that gets rained on when it is open.
Softwood costs a little more and needs knotting solution over the knots before priming, or they bleed through the finish months later. It takes a knock better than MDF and is easier to repair convincingly.
Hardwood such as oak earns its price only where you intend a stained or clear finish. If it is going to be painted, you are buying grain you are about to cover.
Setting the reveal
The reveal is the strip of door lining left showing between the inside edge of the lining and the inside edge of the architrave. It is usually 5 mm to 10 mm, and 6 mm is a common default.
It does two jobs. It leaves clearance for the hinge knuckles and the door furniture, and it turns the edge of the lining into a deliberate line instead of an accidental one. A lining that is fractionally out of square is invisible behind a consistent reveal and obvious behind an inconsistent one.
The number matters much less than the consistency. Set it once and use the same figure on every opening in the house. Mark it with a marking gauge, a combination square or a scrap of board cut to the width, and pencil it right round both legs and the head before you cut anything.
Before any of that, check the lining sits flush with or slightly proud of the finished plaster. If the plaster stands proud, the architrave rocks and will never sit flat against both surfaces - the fix is to ease the plaster back along the line the architrave covers, not to force the trim down onto it.
Working out how much you need
Architrave is counted per opening, not off the room perimeter. That is the whole difference between it and the other two trim runs in a room:
reveal = 5 - 10 mm, the same on every opening (6 mm is a common default)
leg = floor to the inside top corner of the lining + reveal (short point of the mitre)
head = lining width + 2 × reveal (short point to short point)
+ the architrave width at each end (out to the long points)
one side = 2 legs + 1 head
doorway = 2 sides, unless one face is inside a cupboard or an unfinished space
For a standard 1981 × 762 mm door that puts each leg a shade over 2 m and the head under a metre, which is why architrave is stocked in 2.1 m lengths and why many merchants pack it as a set for one side of a door.
The count that catches people is the second side. A door between two rooms is finished on both faces, so one doorway is two sets, and a cased opening with no door in it is the same. Only a cupboard, or an opening into a space that is not being finished, takes a single side.
Add a spare length across the job rather than a percentage per opening. Waste on architrave is not steady trimming loss - it is the occasional blown mitre, and that costs a whole leg.
Two things worth ordering in the same pass: the skirting and any plinth or corner blocks, so the profile, the timber and the primer batch match across the room.
The calculator above sizes the skirting run and an optional second profile at the ceiling. It does not size architrave, because architrave is not a perimeter job - and note the symmetry, because it is a useful check on your own figures: every doorway you subtracted from the skirting run is a doorway you now add back as two sets of architrave.
Cutting and fitting
Work legs first, head last. It is the order that removes cumulative error, because the head is measured between two pieces that are already fixed rather than off a tape reading taken before anything is up.
- Mark the reveal all the way round the lining - both legs and the head.
- Cut the legs. Square at the bottom, 45 degrees at the top, with the short point of the mitre landing on the horizontal reveal line. Stand each leg on the floor, not on the finished floor covering unless it is already down.
- Check the corner angle with a bevel before you cut. Linings get pushed out of square by plastering, and where the corner is not a true 90 degrees the difference is split between the two cuts rather than forced.
- Fix the legs, keeping the reveal exactly on the pencil line the whole way up.
- Measure the head between the two fitted legs at the long points, cut both mitres, and offer it up before fixing.
Fixing is a bead of grab adhesive on the back plus pins or lost-head nails into the lining and into the studwork behind the plaster - the adhesive holds it flat, the pins hold it while the adhesive goes off. Punch the heads below the surface and fill them in the same pass as the mitres.
Glue the mitres. A little PVA on both faces and a pin driven through the corner from the top keeps the joint shut as the timber or MDF settles. An unglued mitre is the joint that opens first.
Fit the architrave after plastering, once the wall has dried, and before the skirting.
The skirting junction
The skirting arrives at the foot of the architrave and has to die into it. Three ways it gets resolved:
- Architrave thicker than the skirting. The skirting butts square into the edge of the architrave and the small difference in thickness reads as a deliberate step. This is the normal modern answer.
- A plinth block. Deeper and thicker than both, it takes the architrave above and the skirting either side, and resolves any thickness difference outright. The traditional period detail, and the most robust.
- Both the same thickness. It works, but it is unforgiving: any bow in the skirting or any variation in the plaster shows up at the joint.
What does not work is skirting thicker than the architrave. Decide the two thicknesses together, before either is ordered.
Common mistakes
- Fitting the architrave before the lining is flush with the plaster. It rocks, and it never sits flat afterwards.
- Marking the reveal by eye. It wanders, and a wandering reveal is the most visible fault on a trim job.
- Buying architrave thinner than the skirting. The step at the foot of the door cannot be fixed later.
- Assuming the top corners are 90 degrees. Check with a bevel; plastering moves linings.
- Cutting the head off a tape measurement. Fit the legs, then measure between them.
- Forgetting the second side of every doorway. One door is two sets.
- Leaving the mitres dry. Glue them and pin through the corner, or they open.
- MDF in a bathroom. It swells if it gets wet and does not come back.
Frequently asked questions
What is architrave?
Architrave is the moulding that frames a door or window opening. It sits over the joint between the door lining (or window board and reveal) and the plastered wall, and it covers the gap and the crack that joint develops as the timber and the plaster move at different rates. It is also the piece the skirting board runs into at floor level, which is why the two are chosen together rather than one after the other.
What size architrave should I use?
Most British merchants stock 69 mm and 95 mm as the mainstream widths, with narrower 44 mm and 57 mm sections for tight spaces and wider Victorian patterns for period rooms. Thicknesses are commonly 15 mm, 18 mm, 20 mm and 25 mm. The width is mostly a matter of proportion - a taller room and a taller skirting carry a wider architrave - but the thickness is not a free choice: it should be equal to or slightly greater than the skirting, so the skirting dies neatly into the edge of it instead of standing proud.
How much architrave do I need for a door?
Work per opening, not per room. One side of a doorway takes two legs and one head, and a door between two rooms needs that on both faces, so a single doorway is usually two sets. The legs run from the floor to the inside top corner of the lining plus the reveal, which for a standard 1981 mm door lands a shade over 2 m; the head runs the width of the lining plus the reveal at each side, plus the width of the architrave itself at each end to reach the long points of the mitres. Add a length for waste over the job as a whole, because a blown mitre costs you a whole leg.
What is the reveal on an architrave?
The reveal is the strip of door lining left showing between the inside edge of the lining and the inside edge of the architrave - usually somewhere between 5 mm and 10 mm, and 6 mm is a common default. It is there for two reasons. It gives the eye a deliberate line rather than an accidental one, and it leaves room for the hinge knuckles and the door furniture. What matters far more than the exact figure is that it is the same all the way round every opening in the house, so mark it with a gauge or a scrap of board rather than by eye.
Should architrave be thicker than skirting board?
The same thickness or slightly thicker, never thinner. The skirting board runs horizontally into the side of the architrave, so if the skirting is the thicker of the two it stands proud and leaves a step at the bottom of the door casing that is very hard to make look intentional. Where the two end up the same thickness, a plinth block at the foot of the architrave is the traditional resolution - a deeper, thicker block that both pieces die into.
Does architrave go on before or after the skirting board?
Architrave first, skirting second. The skirting is the piece that has to meet something, so you fit the frame around the opening and then cut the skirting to run into its edge. Doing it the other way round means scribing or trimming skirting that is already fixed, and it is the usual reason a job ends up with a filled gap at the bottom of the door casing.
How do you cut architrave corners?
The two top corners are 45 degree mitres. Cut and fix the two legs first - square at the floor, mitred at the top - then measure the head between them and cut it to the two long points, which removes the cumulative error you get from cutting all three pieces off the tape. Check the actual corner with a bevel before you assume 45 degrees; a lining that has been pushed out of square by the plastering wants the difference split between the two cuts. Glue the mitre and pin through the corner to hold it shut while it dries.
Can you fit architrave without mitres?
Yes, and there are two ways. Corner blocks (rosettes) sit at the two top corners and let all three pieces butt into them square, and plinth blocks do the same job at the floor - both are period details and both suit a room where the lining is too far out of square to mitre convincingly. The other way is a square-edge section butted at the head, which is a plain modern look. Some contemporary work does away with architrave altogether and uses a shadow-gap bead at the plaster edge, but that is a plastering decision made long before the trim goes on.