Quick answer: choose a door lining by measuring the finished thickness of the wall where the lining will sit. Do not rely only on a rule such as “this stud size plus plasterboard needs this lining”, especially on an existing wall. Plaster, fresh skim, uneven finishes and older construction can all change the final depth.
Measure the wall you actually have, then choose the lining depth that gives the closest practical fit.
Door lining sizes we stock
| Nominal lining size | Approx. finished depth | How to choose |
|---|---|---|
| 32 × 115mm | Approx. 108mm | Choose when the finished wall thickness is closest to 108mm. |
| 32 × 138mm | Approx. 132mm | Choose when the finished wall thickness is closest to 132mm. |
| 32 × 150mm | Approx. 145mm | Choose when the finished wall is deeper and 145mm is the closest suitable option. |
The first dimension is the nominal timber thickness. The second dimension is the nominal depth of the lining. After machining, the actual finished dimensions are smaller than the nominal sizes.
Why we do not recommend choosing from the wall construction alone
You will often see door lining size guides that match a lining directly to a particular stud, plasterboard or masonry build-up. That can be useful as a rough guide when designing a completely new wall, but it is not the best way to choose a lining for an existing opening.
For example, a brick-and-plaster wall may have been skimmed again during renovation. The construction underneath has not changed, but the finished wall is now thicker. If you choose the lining from the original brick-and-plaster rule rather than measuring the finished wall, you can end up with a lining that is too narrow.
Our advice is simple: measure the finished wall first.
What if the lining is slightly too narrow?
If the lining finishes around 2mm narrower than the wall and the frame is being painted, that small difference can normally be dealt with during filling and finishing.
Once the difference becomes more than that, we would normally move to the next lining size up and plane it down to suit rather than trying to hide a larger mismatch with filler.
What if the lining is too wide?
A lining that is wider than the finished wall can be reduced to suit. This is why, when you fall between the stocked finished depths, choosing the next size up and planing it down is usually the better approach than starting with a lining that is significantly too narrow.
When should I measure the wall?
The dimension that matters is the finished wall thickness. If plasterboard, plaster or a fresh skim is still to be added, allow for that finished build-up rather than measuring only the unfinished structure.
Do I need a fire-check door lining?
Our standard stocked softwood door lining kit is not a fire-check door lining. Fire-check door linings are available to special order where the project requires one. Do not substitute a standard lining where a specified fire-rated door set or lining is required.
Choosing your lining
Start with the finished wall depth and compare it with the three finished lining depths: 108mm, 132mm and 145mm. Choose the closest practical size, allowing for a very small finishing difference or selecting the next size up if it needs to be planed down.
