A made-to-measure concealed door lets you put a flush, frameless door almost anywhere: a tall opening, a doorway that’s an odd width, a floor-to-ceiling feature or a hidden door in panelling. The catch is that, unlike a standard door, there’s no architrave to cover small mistakes. The frame is built into the wall and plastered in, so accurate measurements are everything.
This guide explains which measurements a supplier needs, how to take them, what can go wrong, and how to build lead times into your project so the frame arrives before the plasterer does.
Do you need made to measure, or will a standard size work?
Start by checking whether a standard size fits. Most UK internal doors come in a handful of common sizes, and our UK standard interior door dimensions guide lists them. Standard concealed door sets are usually quicker to get hold of and simpler to order.
Made to measure makes sense when:
- The opening is taller or wider than standard, or an unusual size you don’t want to alter
- You want a floor-to-ceiling door
- You’re matching several doors along a corridor to one design height
- The door needs to align with panelling, joinery or a feature wall
Remember that with a concealed door the frame goes in before plastering, so you can often adjust the opening to suit a standard frame during building work. It’s worth weighing up both options with your builder.
Know which size you’re measuring
Door suppliers use several different measurements, and mixing them up is the most common ordering error.
- Structural opening: the raw gap in the wall, brick to brick or stud to stud, and floor to the underside of the lintel or head. Latham’s Steel Doors describes it as the opening measured without any tolerances removed.
- Frame size: the outside dimensions of the frame being manufactured. It has to be smaller than the structural opening to leave room for fixing and packing.
- Door leaf size: the door itself.
- Clear opening: the usable gap you can walk through once the door is open.
When you send measurements, say which one you’ve measured. For concealed doors, most suppliers want the structural opening plus the finished wall thickness, and they work out the frame and leaf sizes from there.
How to measure for a concealed door
You’ll need a good tape measure, a long spirit level and a notepad. Measure in millimetres.
1. Measure the width in three places
Measure the width of the structural opening at the top, middle and bottom. Write all three down and use the smallest figure. Walls are rarely perfectly straight, and an opening that’s wider at the top than the bottom will catch you out if you only measure once.
2. Measure the height in two or three places
Measure from the floor to the underside of the lintel or head, on the left, on the right and, for wide openings, in the centre. Again, use the smallest figure.
The crucial question is: what floor are you measuring from? If the final floor isn’t down yet, you need to know its full thickness, including screed, underfloor heating, underlay and the finish itself, and allow for it. A door that clears the bare subfloor can scrape once tiles or engineered boards go down.
3. Check the diagonals
Measure corner to corner both ways. If the two diagonals are noticeably different, the opening is out of square. A competent installer can pack out small variations, but significant problems, such as a sagging lintel or a twisted stud, should be fixed before you order a made-to-measure frame.
4. Check plumb and level
Hold your level against each side of the opening and across the head. Concealed frames must be fitted plumb, level and square, because the door sits flush with the wall and any error shows. If the walls themselves lean, tell your supplier.
5. Measure the finished wall thickness
Measure from the finished face on one side of the wall to the finished face on the other, including plasterboard, skim, tiles or panelling. If the wall isn’t finished yet, list the build-up instead: stud or block size, board thickness on each side and plaster thickness. Concealed frames are designed for specific wall build-ups, and some have minimum wall or stud sizes. Our Frameless Hidden Door, for example, specifies a minimum 63mm stud.
6. Note the wall type
Tell your supplier whether it’s timber stud, metal stud, blockwork or brick. It affects how the frame is fixed. Our SF-LINE aluminium flush door frame is made to size and comes with wall anchors for both plasterboard and solid walls.
Decide on opening direction and handing
With a concealed door, the door is flush with the wall on one side only, so you need to decide:
- Push or pull: whether the door opens away from you or towards you when you approach it from the flush side
- Left or right: which side the hinges are on
Italian manufacturer Invisible Door’s technical data sheet describes a simple way to define this: imagine standing outside the room you’re entering. If you push the door to go in and the hinges are on your right, it’s a right push door.
Several of our concealed sets are reversible, which takes some pressure off this decision. The Concealed Omega Primed Door Set and the xREVERx flush reversible hinged door system can both be set up as left or right, push or pull. The xREVERx is only available in standard dimensions, though, so check it suits your opening.
For more on why the flush side matters for skirting, adjacent doors and drawings, see our guide to concealed door frame details.
Other details to confirm before ordering
- Door weight and finish: if you plan to clad the door with panelling or mirror, tell the supplier so the hinges can be specified to suit. Our concealed door hinges guide explains why weight matters.
- Door thickness: concealed systems use particular leaf thicknesses. The Omega set is listed with 45mm and 56mm leaf thicknesses, while the SF-LINE frame needs a door at least 40mm thick.
- Handle or handleless: handleless doors need a push-to-open touch latch rather than a standard magnetic latch.
- Fire rating: if the door must be a fire door, you need a tested fire-rated set, not a standard concealed door made to a special size.
- Fitting tolerances: don’t assume a fixed deduction from the opening. Each manufacturer specifies its own tolerance between structural opening and frame, so let the supplier calculate the frame size from your structural opening measurements.
A simple measurement sheet
| Measurement | Reading 1 | Reading 2 | Reading 3 | Use |
|---|---|---|---|---|
| Width (top, middle, bottom) | Smallest | |||
| Height (left, centre, right) | Smallest | |||
| Diagonals | – | Compare | ||
| Finished wall thickness | – | Note build-up | ||
| Floor finish to come (mm) | – | – | Add to height |
Take a photo of the opening with your notes and send both with your enquiry. It helps the supplier spot anything unusual.
Lead times: plan ahead
Made-to-measure frames and doors are manufactured to order, so they take longer than stock items. At the time of writing, our product pages list:
- Concealed Omega Primed Door Set: bespoke sizes around 30 days, with stocked standard sizes 2 to 5 working days
- Bespoke Concealed Door Set: made to measure up to 3m high, with a 4 to 6 week manufacturing lead time
- SF-LINE aluminium flush door frame: approximately 15 working days, made to size up to 3m high and 1m wide
Always check the current lead time on the product page or with our team before you commit to a programme, as they can change.
Because the frame has to be fixed before plastering, work backwards from your plastering date. Order early enough that the frame is on site when the opening is ready, and allow time for checking the delivery. The door leaf can follow later, since it’s hung after the wet trades have finished.
Frequently asked questions
Should I measure the old door or the opening?
Measure the structural opening, not the old door or frame. For a concealed door, the old lining and architrave will be removed, and the new frame is sized from the raw opening and wall build-up.
What if my floor isn’t finished yet?
Find out the full thickness of the final floor build-up and give that to your supplier. The frame is set to the finished floor level, so this figure directly affects the door height.
How tall can a made-to-measure concealed door be?
It depends on the system. Our Bespoke Concealed Door Set and SF-LINE frame are both listed as available up to 3m high, while the Omega set lists leaf heights up to 2,500mm.
Can I measure up myself or do I need a fitter?
Many homeowners measure up themselves using the steps above. If the opening is out of square, the walls aren’t plumb or the floor build-up is uncertain, it’s worth having your builder or fitter check the figures before you order.
Can a made-to-measure concealed door be returned?
Made-to-measure products are manufactured to your sizes, so they’re usually treated differently from stock items. Check the terms on the product page and ask our team before ordering.
Get a quote for your concealed door
Send us your measurements, wall build-up and photos, and we’ll help you choose the right made-to-measure concealed door. Explore our made-to-measure service or browse concealed and flush to wall doors.
