When you choose a pocket door frame, the most important number isn’t the door width. It’s the finished wall thickness. Get it right and the pocket wall lines up neatly with the rest of the partition, the jambs fit first time and the architrave sits flat. Get it wrong and you’ll be packing out studs or trimming linings on site.
This guide explains how finished wall thickness is worked out, and walks through three common builds: 100mm, 115mm and 145mm.
What is finished wall thickness?
Finished wall thickness is the total depth of the wall once it’s built and boarded: the stud or pocket door frame in the middle, plus the plasterboard on each side. Skim plaster adds a few millimetres on top, but kit makers generally quote the boarded thickness.
The basic sum is simple:
Frame or stud depth + board on side one + board on side two = finished wall thickness
With a single layer of standard 12.5mm plasterboard on each side, you add 25mm to the stud size. With two layers each side, as fire-rated systems often require, you add 50mm.
Why it matters for a pocket door frame
A pocket door frame replaces a section of studwork, so it needs to match the depth of the studs either side. If it doesn’t, the plasterboard won’t sit flat across the frame and studs.
The finished wall thickness also decides:
- which jamb or lining kit you need, as these are sized to the finished wall
- how much room there is inside the pocket for the door to slide without rubbing
- whether the system can be fire-rated, since FD30 builds usually need extra boarding
The 100mm build
A 100mm finished wall is one of the most common partition thicknesses in UK homes.
How it’s made up
Rocket Door Frames publishes the build for its 75mm frame: 75mm timber studwork with a single 12.5mm plasterboard layer each side gives a 100mm finished wall.
Which pocket door frame?
Our 75mm pocket door kit is designed for 75mm and 100mm timber studs. With 75mm studs you get a 100mm finished wall. Jambs are available as an option sized for a 100mm wall.
The Ermetika Absolute Evokit frameless pocket door system is also suited to 100mm walls if you want a frameless finish with no architrave.
Related builds
The same 75mm Rocket frame can go into 100mm timber studwork, giving a 125mm finished wall. For a slimmer wall, the 70mm pocket door kit suits 63mm CLS or 70mm steel studs, giving a 95mm finished wall. Rocket notes that with 63mm CLS you add a 6mm plywood layer to one side to bring the stud up to 70mm.
The 115mm build
A 115mm wall is common where builders use 89mm CLS timber, a widely available stud size.
How it’s made up
According to Rocket, 89mm CLS studwork with a single 12.5mm plasterboard layer each side gives a 115mm finished wall. With 92mm steel studs, the finished wall is 115-117mm.
Which pocket door frame?
Our 90mm pocket door kit fits 89mm CLS or 92mm steel studwork. It suits 35-44mm doors up to 60kg.
The Easi pocket door kit with soft close is also designed for a 115mm finished wall, for doors up to 914 x 2032mm and 40kg, with soft close included.
Why choose 115mm?
A 115mm build matches partitions framed in 89mm CLS, which is a common stock size at builders’ merchants. It also lines up with a wall built from 89mm CLS, so you don’t need to change stud size around the opening.
The 145mm build
A 145mm finished wall is usually linked to fire-rated pocket doors, where two layers of fire-rated board are needed on each side.
How it’s made up
P C Henderson’s Pocket Door Pro fire liner kit is a good example. Its specification gives a 120mm frame width before boarding and states that two layers of 12.5mm FD30-rated fire board must be installed on both sides, giving a 145mm finished wall. MB Direct lists its Enigma FD30 pocket kit with the same total: a 95mm frame with four layers of 12.5mm plasterboard in all.
Rocket’s FD30 equivalents
Rocket’s FD30 kits use two layers of 12.5mm board each side too, so the finished walls are thicker than the standard versions:
| Rocket frame | Standard build | FD30 build |
|---|---|---|
| 70mm | 95mm | 120mm |
| 75mm | 100mm | 125mm |
| 90mm | 115mm | 140mm |
We stock the FD30 70mm pocket door kit for a 120mm finished wall, alongside FD30 75mm and 90mm versions for 125mm and 140mm walls.
Large doors
Wall thickness can also go up for very big doors. Eclisse, for example, states that for its bespoke pocket systems, door widths over 1300mm and heights over 2600mm need a finished wall thickness of 150mm.
How to choose your pocket door frame
- Measure your existing studs if you’re working with an existing partition, or decide the stud size for a new one.
- Decide on boarding. One layer of 12.5mm board each side is standard; fire-rated or acoustic walls may need more.
- Add it up to get your finished wall thickness.
- Pick a frame made for that stud size and finished wall.
- Order matching jambs for the finished wall, if they’re not included.
- Check the door against the frame’s thickness and weight limits.
Common wall thickness mistakes
- Forgetting the second layer of board on fire-rated walls, which leaves the jambs too wide.
- Mixing stud sizes either side of the frame, so the plasterboard bows across the pocket.
- Ordering jambs for the wrong wall, for example 100mm jambs on a 125mm wall.
- Using over-long screws through thicker board layers, which can poke into the pocket and scratch the door.
- Not allowing for tiles. In bathrooms, tiles add thickness on one face, so plan the architrave or trim detail before you start.
Quick reference
| Finished wall | Typical build | Example frame |
|---|---|---|
| 95mm | 63mm CLS + 6mm ply, or 70mm steel, + 12.5mm board each side | Rocket 70mm |
| 100mm | 75mm timber + 12.5mm board each side | Rocket 75mm |
| 115mm | 89mm CLS or 92mm steel + 12.5mm board each side | Rocket 90mm, Easi |
| 125mm | 100mm timber + 12.5mm board each side | Rocket 75mm |
| 145mm | Fire-rated frame + two layers of 12.5mm fire board each side | Henderson Pocket Door Pro fire liner |
Frequently asked questions
What is the minimum wall thickness for a pocket door?
It depends on the kit. Rocket’s 70mm frame gives a 95mm finished wall with 12.5mm plasterboard each side, and Eclisse offers systems from 95mm finished wall thickness.
Can I fit a pocket door frame in a 100mm wall?
Yes. A 75mm frame in 75mm timber studwork with 12.5mm plasterboard each side gives a 100mm finished wall.
Why are fire-rated pocket door walls thicker?
FD30 systems usually need two layers of fire-rated board on each side, adding 50mm rather than 25mm to the frame.
Does skim plaster change the finished wall thickness?
It adds a few millimetres, which is usually absorbed by the jambs and architrave. Check your kit’s instructions if you’re using thicker plaster.
What if my studs don’t match any frame?
You can pack studs out, for example with ply, or rebuild the section of wall around the pocket. Ask us before ordering if you’re unsure.
Find the right pocket door frame for your wall
Browse our pocket door systems, or call us with your stud size and door size and we’ll help you choose.
