How we have done the lime rendering
Our mix is the same as ever 3sand 1Lime 1Sieved torchis, however in the scratch coat we have used “yak hair” to help bind it all together.
I have no idea where to buy it in France as nephew Will gave me a few bundles each one about 5 cms across by 7 long, it was “yak hair” but it feels the same as horse hair.
When you have your mix going you have to separate it up and sprinkle it in, and you use enough so you can “see it” in the mix. You also need to free it from the blades of the mixer as it sticks a bit, but make sure you never put your hand or try and use a spade into a moving mixer as it is a sure fire way to end up badly injured.
I cut the long handle from a garden hoe down to about a meter and used this to free the hair from the blades and to help scratch out any residue in the mixer after each mix as the mud in the mix sometimes makes it a bit sticky for the mixer
Another alternative is to use chopped hemp which I know is readily available in France, not only does this bind and work well as a scratch coat it adds insulation properties to the render. It is excellent to use on the outside as when it dries it looks like it has been there for ever.
Regardless of the hair/hemp, your mix consistency will be about half way between double cream and clotted cream. Once you have given it a thorough mixing give it 10 minutes to settle while you prep the area.
If you are rendering over a torchis (cobb) wall you may need to give it a once over with a flat bladed spade first to knock off any lumps, it will also help you identify any holes. Then take a hose with a spray attachment and give the area you are about to do a good soaking. I don’t mean a little bit damp I mean “wet” then give it a few minutes to soak in.
With stone walls the same applies on getting it wet, but concentrate on the pointing joints and make sure they are “wet”
With concrete block just give it a good wetting down or else it will suck the moisture out of your mix too quickly.
Lime render wont stick to plasterboard so don’t waste your time.
I had to get some “render board” or “cement board” as it is known because it wasn’t possibly to build up the tops of the slanted walls traditionally.
To get the render to adhere we made a watery mix of cement sand mud and coated the board in it. We then cut the board to size and fitted in place then screwed chicken wire to that so it would hold the render. (It worked)
Make sure you have a good solid platform that is at a good height so that ideally you can swing your arm from knee to just over head height. We use gorilla buckets to hold the muck although sometimes for the high bits I was using a long handled “Cornish shovel” and lifting from barrow to his hawk enough for him to work with. Takes a bit of timing but once we got going it was fine.
Using a square trowel or the end of a “float” use your wrist action to flick (at speed) about “half a fist full” sized lumps of render into any holes to build them up level (or near enough) with the main surface. Do this for the whole area you can reach from your platform.
Using your float land a large dollop of muck on the “hawk” (that’s the flat thing about a foot square with a handle underneath) and then work it a few times with your float (that’s the oblong trowel thing with a handle above the blade). The purpose of this is to remove any excess air and make it more workable.
Then in one sweep force the muck onto to the wall and spread it out (normally in one direction. Do this over and over again moving as you go.
Don’t spend to much time mucking about with it as you will just pull it back off the wall again.
I tend to start at the top and work my way along and down trying to get a good even layer onto the wall.
The beauty of lime render is that later on you can “sponge it up”.
The timing of using the sponge is fairly critical as you don’t want to start on it too early as you stand the danger of pulling it off the wall.
Once nearly dry but still will dent if you push your thumb hard against it you use a sponge board to even it out. They are sold in all Bricos. It is about 20 cms by 15 and has a sponge stuck to a board or plastic with a handle on the other side. You dip it in water shake off any excess and start to work the render with smooth circular strokes. You will be amazed as any imperfections or small cracks disappear.
As it is just the first coat you don’t have to worry to much about getting it too fancy a finish.
Once you have finished the sponging and you can scratch it up to give the finish v coat a “key” to adhere too.
I cut a 6 inch length of chevron and hammered some 6 inch nails through it. You then run this over the sponged render going in about half a cm or so. Don’t go too deep or you stand the risk of pulling the render off.
Give it a day or two to dry and then damp it down (don’t get it soaking but damp is ok) starting at your original start point begin the top or finish coat using the same sort of swinging motion.
You use the same mix but using fine sand (0.2) instead of coarse to repeat the operation.
With this final coat the sponging is crucial as if you are too heavy handed you will leave marks.
The more you do the better you get at it and as you practice the technique on the scratch coat you will be much better by the time you reach the top coat.
I still have plenty scratch coating to do and I am getting more and more
confident as I go along.
The bathroom will be lined with water resistant plasterboard and tiled. Even though it will be covered we are scratch and top coat rendering between the frames of the stud work. This is for me to practice my top coating but also so we can then experiment with “lime wash” using different pigments until we finds the right recipe and colour for the various parts of the house.
I hope that explains the process so far but feel free to comment on our render or ask any questions.
Cheers
Bentley
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