Wall and ceiling repairs
Table of Contents
Starting by opening up the cracks and removing drummy areas and any gypsum plaster patching around the three doorways.
The bulging plaster over the verandah doorway may be quite old and possibly resulted from pulling the picture rail off the wall. Total collapse appears to have been avoided by replacing the original lime plaster covering the timber lintel with a strip of cement plaster applied over a grid of tacks hammered into the lintel (images 1). This appears to have been done prior to the grass-green paint.
The light and power wiring chased down the wall from the ceiling has also been removed.
1. Removing bulging plaster over the external door.
2. External (verandah) doorway
Removing loose mortar left a couple of large and deep voids, which will be filled with stone pinnings to reduce the volume of new mortar that goes in and thereby minimise shrinkage that could lead to cracks in the future.
3. Bedroom two doorway
Just a little dubbing out needed along the top of the lintel mainly.
4. Sitting room doorway
A large deep void above the centreline of the door had been filled with mortar and may have contributed to the vertical crack above it. It will be filled with stone pinnings and mortar during dubbing out.
To provide a key, 6 x 6mm wire mesh was stapled to each lintel using the original raised chisel cuts to provide standoff of a couple of millimetres. I'm relying on the timber not shrinking any further than it had already over the past 140 years.
A week earlier I'd mixed 120ltrs of 3:1 sand plus lime putty and stored it in 20ltr pails, 60ltrs of which also had fibres added as a trial batch. Now, after pouring off the excess water used to cover the mix in the pails, the consistency was still homogeneous and good for throwing onto the stone and timber/mesh substrates before trowelling.
5. External (verandah) doorway.
6. Bedroom two doorway.
7. Sitting room doorway.
After a week with initial regular dampening and then allowed to dry out, the scratch coats took a lot of water before they appeared ready to take another coat.
The straightening coat has been completed on all patches but the sitting room doorway patch (images 7) needed a second scratch coat due to the thickness of the original plaster. The window patch also required a second scratch coat applied. The cracks and chases that I'd opened up have been filled.
I've decided not to restore the picture rails and therefore not restore the nailing plugs. I've filled the holes with mortar and pinnings leaving any remaining plugs and will skim a finish coat over. Later I'll install a modern gallery hanging system in all rooms.
There appear to be three layers of paint on the upper section of the walls. Two layers of water based paint, white over chartreuse, which scraped off easily together using a sharp carbide wall stripping blade. The chartreuse had been applied over a beige sand colour layer that could be linseed oil based causing the water based paint to not bind well. I could heat strip the oil based layer but it was much easier and cleaner to brush on a stripper (in this case Dumond SmartStrip) in a thin coat then scrape off after an hour. I had to repeat this all over to get a gummy residue off which could have been some kind of clear sealer primer.
The green layer covers the walls and ceiling entirely and there is a stensiled black painted frieze under the oil layer extending about 200mm down from the ceiling. I believe it's a lily motif. The leaves don't look like strappy tulip leaves and there's the fleur de lis motif.
A final going over with steel wool and a mild solvent should clean the residue off.
9. The original stenciled frieze continues around the room.
The green layer is milk paint
Milk paint uses casein as the binder so to test this I need something that dissolves casein. Modern paint strippers don't work on milk paint and have had no effect on this paint, which is the first clue. So I mixed up a milk paint stripper recipe which does soften this paint, so it is reasonably confirmed to be milk paint on the walls and ceiling.
I'm very impressed by how rebust this paint coating is on lime plaster. It doesn't appear to have deteriorated in the 140 years it's been on except at the top of the wall directly above the fireplace where it was possible, with some effort, to scrape it off with a sharp carbide paint scraper. Everywhere else I made no impression on it at all.
Finish coat patching
The spots where the finish coat broke away as the lining battens were removed have had their initial patching done using a 1:1 lime putty and fine sand mix. Generally this has gone ok but steel trowelling to get a smooth finish to match the rest of the wall was difficult with small areas. I can get it flush but the new plaster is still too rough because the intact surface prevents the trowel from applying the right action to the new plaster to smooth it. I've scraped back these patches and applied some much finer plaster (3:1 old hopefully carbonated dry lime [calcium carbonate], to lime putty), which works well for very shallow depths, e.g. where I only need to smooth over a rough surface, filling pores. In fact this works so well that the texture is identical to the touch with no perceptible change when transitioning from wall to patch to wall again. I've applied the same fine plaster to deeper patches of about 1mm and I will get crazing in these cases, which disappears if I wet and trowel smooth again, provided I don't leave it too long (several hours).
I used the same fine plaster as the finish coat on the large re plastering patches over the doors and window. These areas were a lot harder to get right and I had to keep the trowel and plaster quite wet during finishing, literally spray and trowel, spray and trowel. If the plaster or trowel weren't wet enough the trowel would tend to suck the plaster off the wall at the low angle used.
All the wall patching is now done. A big general cleanup is all that's needed, which will be after the ceiling is done.
10. Finish coat patching
11. Finished patching
The ceiling is not flat but there is no sagging due to render coming away from laths or laths coming away from joists. The major cracks, which are only hairline, appear to be due to joists bowing over time. There are some cracks where there is a slight height difference on either side (approximately 0.1mm), small enough to sand level or skim and feather at worst.
The cracks are quite old and do not appear to have gotten worse since. Some are possibly the result of previous works that were done in the roof space, such as the ventilation ducting in the mid-late 1930's or electrical wiring in the 1950's and 1980's.
The ceiling has the same green milk paint as the walls so the original room was very dark but with the right furnishings and decor would have looked quite elegant. It was later painted over with the same oil paint and colour as on the upper walls, then later with a water based flat white paint. The existing paint layers are in good condition, i.e. not flaking etc so I'm not considering stripping it back at this stage, although it does appear to strip back to the milk paint layer using a sharp carbide scaper blade a little easier than did the walls, but it is still tough going.
12. Ceiling cracks sanded to remove ridges and dissimilar levels.
The old rough patching done around the fireplace needed to be fixed now that the fireplace has been opened up and will be either visible or tiled. It was easy to slap on a flattening coat using my regular render mix. It's convenient having it in buckets ready to go anytime I need some but the finish coat was the first time I've used a mix proportioned differently.
Usually a finish coat is around 1:1 fine sand to lime putty and for me the quickest way to get that was to add lime putty to some of the already mixed flattening coat render.
82. Additional rendering around the fireplace.
One measure of putty to two measures of render gave me a 6:5 sand to putty ratio by volume.
After trowelling the finish coat on it was relatively uneven, so a sponge float was used to even out and flatten the surface. The sponge picks up render from high areas and deposits it in lower areas but it also brings sand grains to the surface producing a gritty texture. In this case this was not the desired finish so it was then steel trowelled to push the grit back into and smooth the render. I used the swimming pool trowel to avoid creating ridges in the surface.
One measure of render consists of 1 measure of sand + 1/3 measure of putty by volume exactly filling the voids. Therefore I had 6/3 sand including 2/3 putty together with the additional 3/3 putty, which gave me 6/3 to 5/3 or 6:5. I could have gone 3 of render and 2 of putty to get a 1:1 mix.