What was original
How we tell what was original from what was added
An old wall is a stack of decisions made by different people. Before we repair it, we read the stack.
We start with a flat hand and a knuckle: a dull sound is plaster that has let go of its lath. Then we look at the wall in raking light, with a lamp held low and to one side, so that every patch, wave and old crack throws a shadow.
Where a wall is already open, an edge shows the layers in section. The lath, the scratch and brown coats, the finish coat and the paint sit in order, and a later patch shows as a coat that doesn't fit the sequence. Original lime plaster often has animal hair in its brown coat. A cement patch is harder and greyer than the plaster around it.
We photograph every layer we open and mark each one on the survey as original, added later, or not sure. The note on the next section is a sample.
Reading an outside wall
A second sample note
An outside wall, read from one corner. Each number is a layer, marked as the survey would mark it.
- 1
Later: a sand-textured coat
A rough, cement-heavy coat, probably added to even a worn wall. It is shedding from the top down.
- 2
A hard edge
Where the coat has lifted from the brick. A coat that breaks along a line like this is often holding water behind it.
- 3
Original: the brick
Soft brick with its face still intact. It is part of the wall and stays as it is.
- 4
Original: the mortar
Pale lime mortar between the courses. Repair mortar has to be softer than the brick it sits in.
Sample content.
Layer by layer
What is usually original, and what we do with it
| Layer | What we do with it | When we replace it | What is usually original |
|---|---|---|---|
| Wood lath | What we do with itRe-fasten loose lath and re-key the plaster behind it. | When we replace itWhen strips are rotted by a leak or broken across a whole ceiling. | What is usually originalNarrow strips nailed to the studs or joists with gaps between them, so the plaster can push through and key. |
| Scratch and brown coats | What we do with itPatch with a matching mix. Where the plaster is soft but still bonded, consolidate it rather than cut it out. | When we replace itWhen it is powdery or fully detached from the lath. | What is usually originalTwo coats of lime or gypsum plaster over the lath, often with animal hair for strength. |
| Finish coat | What we do with itSkim only the repaired area and blend it into the surface around it. | When we replace itWhen earlier skim coats have failed in layers and can't be keyed back. | What is usually originalA thin, hard coat, trowelled smooth, that carries the wall's texture and sheen. |
| Cornices and medallions | What we do with itClean, consolidate and re-attach. Cast or run only the lengths that are missing. | When we replace itWhen most of a run is gone. We make the profile from what remains. | What is usually originalRun in place from a profile or cast in a shop and fixed with plaster. |
| Paint | What we do with itTest before raising dust, clean by wet methods and fill, rather than scrape the detail away. | When we replace itWhen the build-up hides the detail and cleaning can't bring it back. | What is usually originalDistemper, then oil and latex over many years. Under it, often, detail. |
The survey you keep
What is in the survey note
A photograph
Every layer we open, taken straight on and in raking light.
A location
The room, the wall and the spot, marked on a sketch of the plan.
A finding
Original, added later, or not sure, with the evidence beside it.
A recommendation
Keep, repair or replace, and why, in plain words.
The paint note
What we found under the paint, and how the work will be done in a house built before 1978.
A scope
The order of work, the drying time between coats and what you will see on each day.
Have the wall read before anything is touched
A survey is a look at your walls and a written note. It does not commit you to the work.