renovation of our lounge

The walls were still lime plaster, some on masonry and some on lath but all were painted with purple emulsion. They were pitted, some of the top coat of plaster was peeling off and the walls had been chased for re-wiring so it obviously needed attention.

When we bought this house I realised I needed a pretty good plaster recipe, I was not going to be re-plastering everywhere because we are living in the house and removing old lime plaster is a dusty job. I also wanted to avoid the time and cost of complete re-plastering.

My plan was to skim over the walls with a thin coat of lime and then paint with clay paint, repairing what needed to be repaired, patching what needed patching but keeping as much as possible.

The breathing issue is not so relevant with lath and plaster stud walls but is relevant with masonry walls.  But what is important is a good key so I pecked all the walls or scratched them were pecking was a bit too disruptive for the lathing. Pecking or otherwise breaking through the emulsion coating to some degree allows the plaster to breath and with a good coat of lime over the top this is helped further. To aid further adhesion I gave the walls a coat of grip primer.

Once the walls had been prepared I needed a high performance plaster to work with. I devised my own recipe jblime finishingplaster

the walls pecked and primed ready to skim

The first coat of plaster was 3 parts lime putty, one part sharp fine sand and lots of short horse hair applied about 2mm thick.

the beginnings of the final coat of plaster – tinted brown

When the first coat had dried off a bit it was time for the second, 3 parts lime putty to one part sharp fine sand and plenty fine manufactured fibres. I added some brown pigment to create a contrast between this coat and the first so that it was easy on the eyes seeing if I had missed any bits.

The first wall done

The next day I was able trowel the plaster flat and smooth, compressing it and tidying up the edges, it is time consuming but very important.

When it had dried, and being no more than 4mm thick, it didn’t take long the new plaster was painted with Earthborn clay paint. I bought white and tinted it with black pigment to get a light grey, I tend to tint all our paints in the house, one room was tinted with iron oxide I found oozing out of the sea cliffs west of Westward Ho! another room uses paint tinted with Bideford Black also got from the sea cliffs. This time I bought my pigment from heritage cob and lime  who supply my excellent lime putty and sand.

with the furniture in and ready for me to lounge in.Once it was painted and began to dry it was obvious were the damp was as those places were drying much more slowly, I knew they were damp anyway but it is always nice seeing the new plaster dry out after years of not being able to.

Any way thats another room done and now I only have the ground floor to tackle but that wont be until late spring 2018 so we will be living with crumbling plaster and wire chases for a while yet but at least we can watch telly in relative comfort and style.

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The 1:3 ratio

http://www.buildingconservation.com/articles/mythmix/mythmix.htm

This article by Gerard Lynch was published in 2007.

It’s been ten years and still the ready mixed lime mortar producers haven’t fully taken it on board.

The most enlightening statement for me is this:

“under analysis, the majority of historic lime mortars are not commonly found to be 1:3 but typically vary between 1:1½ and 1:2, just as the original mortar makers and craftsmen intended. This is borne out by extensive analysis carried out over many years by The Scottish Lime Centre Trust. (At the last count the organisation has analysed around 4,500 historic mortar samples, approximately 80 per cent of which were from Scotland, 10 per cent from England with the remaining 10 per cent from various other countries.) The average lime:sand ratio on the organisation’s entire database of historic mortar samples is around 1:1½.”   

 

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Stamped plaster work

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Stamped plaster work. Initial trials of stamping lime plaster with wooden blocks using an innovative plaster recipe. The plaster can be used as an ultra fine lime finishing plaster which can be applied 3-4mm thick and simply trowelled smooth but which can also be imprinted with quite detailed patterns.

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the block used here is 3.5 inches square.

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the bigger block is 6 inches square.

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This is a close up of the border of the bigger block showing the detail .

 

 

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how to plaster a wall (first coat)

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start with a bare wall, loose material removed, brushed down and lightly wetted .

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apply plaster around the edge like a frame ; i got the left hand one flat then some horizontal ribs to project the levels to the other side, then complete the right screed

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fill in the blank areas bring level with the frame. This is only the first coat but it is brought level, if it isn’t what is the point? After trowelling I went over it with a couple of straight edges; one long, one short – up and down and side to side sawing movement across the surface just to take off the high spots.

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key with a comb ready for the next coat, which will be easy as this is already more or less level, some shrinkage will cause this first coat to be less level than it was at the start, this wont crack because there is enough hair in it to stop that but it will still shrink.

So there you have it, a very small bit of wall I know but the principles are the same all the time, get the plaster level with the first coat not the second, the second coat just brings the plaster to the correct depth. If your first coat is not level what was it’s purpose?

 

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my Japanese plastering trowels

my-plastering-trowels

These are the only plastering trowels I use.  Starting at 9 on the clock: a medium sized Jigane laying on trowel,  next a little really flexible polishing trowel, at the top a larger jigane, recently used for laying on the finishing plaster, at 3 a medium sized Honyaki finishing trowel which I also use for the finishing plaster. at the bottom a smaller Honyaki which I use both for laying on and compacting the finishing plaster, then at 8 on the clock, my new Honyaki trowel solely for compacting and smoothing. Also three small corner trowels.

 

 

 

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Renovating old domestic plaster surfaces

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applying the first coat of finishing plaster

A testing job for my own recipe JBLime finishing plaster but one that any other lime plaster may well have not managed so easily.

The walls are generally old lime plaster but have been painted with emulsion, wall papered and patched and in places over skimmed with nice pink gypsum. The main patches were done with limelite.

In the picture you can see the new finishing plaster going on (the darker grey)  Areas where limelite was removed and replaced with a new lime plaster and the green is the wall prepared with a grit primer after the wall paper was removed.

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The fire place was a bit of fun. The three walls are gypsum apart from the one on the left which is half plastered in cement. They were all painted with emulsion which was easily scrape off. I keyed the gypsum to get a good mechanical fix for the plaster skim.

The wall can be seen with the grip primer, I did not want to entirely rely on the grip coat so I also keyed the old plaster with my spiked roller (lime plastering plasterboard. with the correct tool and material it works well.)  which has come into its own for breaking through the surface of painted plaster. It takes a fair bit of force but it soon does the job and gives a decent key without making a great lot of damage, it is also useful for stressing the plaster all over so that any loose or suspect bits of plaster are soon found out and can be replaced.

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The final coat applied, all smoothed and flattened. It is still drying here and there; on a job like this, with all the different substrates to contend with, drying is very uneven. The new lime patches at the bottom reached trowelling condition within a couple of hours, the plaster on the cement took two days. The plaster on the gypsum was reasonably quick being trowelled the following day, which just called for patience because as I said, the left hand side was gypsum down to half height then cement, which, to add a little extra difficulty, was set back from the gypsum half about 3mm so it needed and extra coat of plaster. The rest of the grit primed plaster reached trowelling condition about 24 hrs after application.

When I say trowelling I mean flattening, smoothing and compacting.  The window of opportunity for trowelling is quite wide, although there is a sweet point when it is perfect. If you try too early the plaster can form the occasional little bubble and it is very difficult to remove the trowel marks, trowelling too soon is best avoided but there are times when you need to do it, this is when I know that if I leave the trowelling overnight it will go too far and be almost too dry for the trowelling to be easy the following morning, in that situation I can carefully trowel the plaster smooth and then in the morning all I need do is go over again for the final compacting and smoothing.

Of course all this is so much easier when the plaster is flat, undulating plaster is such a chore and for that I find I have to use the really flexible, venetian plastering type trowel, but for all other plastering the trowels I use are rigid, that appears to be the Japanese tradition, rigid trowels for laying on, with practice you can get the plaster pretty flat without the need for floating, and even on this job, which was mainly skimming I used a very rigid Japanese Jigane trowel.  ( http://japaneseplastering.blogspot.co.uk/p/blog-page_10.html)

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Honyaki finishing trowel – the blade is quite rigid with only the slightest amount of flexing under pressure. It compacts and flattens to achieve a very hard wearing lime plaster surface.

 

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Recipe for course stuff

My recipe for course stuff:

3 parts lime putty

1 part horse hair about 30mm long

6 parts sharp sand

method:

put the lime putty in a mixing tub such as a large trug, add the hair and stir it in so that the hair disperses. add half the sand mix with a plaster whisk then add the rest of the sand and mix again.

Some hair will get tangled on the whisk this needs to be taken off before it is used again.

I use a propellor whisk from Refina

MR8 120G Impellor Paddle this grabs less hair than a basket whisk.

 

 

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Tricks of the trade number 1

ribs

This wall, being damp, had over the years been repaired with a host of materials, plaster board, metal lath and cement, universal one coat and gypsum. All that was removed and the wall was pretty undulating and there was a lot of depth to be made up. To make things easier I made five vertical ribs with the plaster and brought them up to the required level for the first coat. I was pushing it a bit as it was plain at least three coats where required but time was not available so I had to do it in two coats and a finish coat i.e a scratch and a float coat. So given the depth I opted for this age old method; with the ribs giving me clear indication  of how much depth there was I got some plain terracotta roofing tiles and built up the thickness with them.

dubbing out

dubbing out with broken roofing tiles

The tiles take the place of some of the plaster and the ribs make sure you don’t pack the wall out too far, the ribs were all on the same level so that I knew that I would end up wit a flat wall.  There were places were no packing was needed and places were two layers were needed. but the process was easy and quick.

make sure the tiles are tapped deep into the plaster

At the end the wall was level and the next day I was able to put the float coat on. Thereby successfully applying an inch and half of plaster in two coats with no risk of cracking.

This technique has been used for centuries and can even be seen in Pompeii.

ready for the float coat

ready for the float coat

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Lime for beginners training course. Cotswolds Rural Skills.

So another course has come and gone.

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We had fun. and sun.

and got a lot of work and learning done.

So what happens on a John Byrne led lime workshop? We start with an introduction to the ingredients: limestone, quick lime, hydrated lime (lime putty), sand. mortar, old mortar, and completing the lime cycle – stone again.

Calcium carbonate, calcium oxide, calcium hydroxide, calcium carbonate

we mix up some mortar, talk about recipes, and where to buy ready mixed mortars ,and when and how, we add horse hair to make  plaster. Then we practice pointing and practice plastering, dubbing out the wall, getting it level or at least not so uneven. The following day we look at finishing the pointing, pressing back and brushing off, we apply finishing plaster to our first days plastering,  smoothing the surface, plastering corners  All this is done on a real building not in some workshop on a concrete block wall, all the work produced by the participants  becomes part of the fabric of the building and builds, course on course, until the building has been repaired, pointed, plastered. The only recycled work is the Plastering on a lath panel. but its good to be able to see both sides.  Then we have a break from plastering and look at limewash and its pigmenting and application, and we end with lime slaking, which lays down lime for the next course.

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I like this too

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