Thorpy's Guide to Lime Rendering for Beginners

Introduction

Most houses have very smooth interior wall surfaces provided by gypsum plaster. This typical pink plaster is a relatively high skill material to work with despite being in an out of building trade for 30 years, I prefer to leave it to specialists. 

Lime render or lime plaster is a sand and lime mix that is easy to work with, and although it does not give the perfectly smooth finish given by gypsum plaster, it has a charm of its own and I like using it, and the finish it provides.  

Lime Rendered Walls with a Slatted Ceiling

For an earthy build, with the right aesthetics lime render can fit very well, but it would likely look a bit odd in a "normal" house. In the above picture I have used a slatted ceiling with lime rendered walls. The two complement themselves rather well. Wooden window frames would have been a nice touch, but they were too expensive.

Fitness. I can cycle about 20 miles in one go over very hilly countryside.  Averaging around 10 miles an hour. . . .. . .  1 day of lime rendering (about 10m2) on my own (mixing, troweling, sponging) and I am dead to the world the next day. So it is best done as a shared job. It can also be a long job. . . . 

Mixing

. . . . .  based on an 0800 - 1700 day your last mix of the day should be about lunch time. Using the method described on this post, you will need 3 or 4 hours setting time before you can finish the work. A load mixed in the mid afternoon might be ready to sponge at 8pm - 9pm. For me that was after dinner! 

Mixing lime render is quite easy. Lime (Natural Hydraulic Lime) and sand (the sand will affect colour!) roughly 3 parts sand to 1 part lime. 

Be very careful not to get any lime in your eye. The worst thing you can get in your eye is a strong alkaline. And guess what; lime is a strong alkaline. If you do get some in I have found that sticking you head in a bucket of water and washing out eye, very very well works to stop any damage. Do not mess about walking to first aid post to get eye wash, or rubbing your eye with a wet towel. Wash out your eye very quickly and well, with tons of water. If irritation persists after washing (it never has for me) then go see a Doctor. 

It is worth keeping a large bucket of water handy for eye washing. My mother-in-law got some lime putty in her eye once, didn't wash it out very well, and the results were quite shocking. The white of her eye ball went bright red and lumpy. Its vicious stuff.  

The below video shows how to mix lime render. It is a warts and all video. The mixing does not have to be 100% precise. 

Put 0.5 bucket of water in a cement mixer. If you don't have one you can hire one. The only thing that goes in the mixer whilst it is switched on is the sand and lime. Do not put your hand inside, do not put your shovel inside. 

Next put in 3 shovels of sand, and a shovel of lime. The end result that you need is something resembling butter creme. It should be soft, and easy to work, but it should keep it shape quite well, when pushed around with a trowel. 

Put in more water or more sand and lime (keeping the ratio 3:1) until it looks right. 

When you are happy with the result tip the lime render in to a wheel barrow, and then scoop some out in to buckets. You then carry these buckets inside.

Tip the buckets on to a "spot" this is any old bit of flat wood. Left over floor boards or a 2ft square of board of any type is ideal. If you can put this "spot" on a table. . . or a stack of blocks it will save your back.

Putting it on the Wall

You will need a hawk and a plasterers trowel as a minimum to put the lime render on the wall. Lime render can be applied as one coat to a concrete block wall. If you are doing partition (wood or steel frame walls) then things might be more complicated. See partition walls for advice. 

Hold the hawk just below the edge of the "spot" and scrape some of the render on to it using the plasterers trowel. It is good to wear rubber gloves. 

If your hawk is aluminium you may notice that it starts to fizz after a while, as the lime render (strong alkaline) eats away at the metal. This serves as a handy reminder not to get any in your eye!

Most people recommend starting at the top of the wall. But to start with just slop it ion the wall, and see how you get on. Perhaps start in a less visible location, so that your first bit of render (likely the lumpiest) will be principally out of view.

Put 4 or 5 hawks worth of lime render on the wall. You will start to see where the lumps are. You can then go back over it. Scraping of high points and filling in low points. You can keep doing this for ages with lime render. Pushing scraping and adjusting until you are happy with the result. This is the beauty of lime render, its workability. 

Once you have it quite flat, then leave it for a few hours until it is firm to the touch. You will then give it a sponge. 

Sponge O'Clock

When you can push the lime render and it only leaves a very fine finger print, and requires a little effort to do so then it is ready to sponge. 

You can use a sponge (decorators sponge) or a sponge float. The latter requires a little more skill, but gives a flatter wall. A sponge float also requires quite a lot of strength to use. 

Refina Sponge Float

I use one of these and a decorators sponge together. You can use the sponge float first to flatten the render and then buff up and smooth little hollows so they blend in using the decorators sponge. Once you have finished sponging simply walk away and leave the render to cure, this will take a few weeks. 

Trust your own judgement, you know what you want you wall to look like. Stand back now and again to look at what you are doing. 

Undo

If at the end of the day you are unhappy with the result, take a shovel and scrape all of the lime render off of the wall. Have another go in a few days time. I did this once. It was a bit depressing, but it good to know you can just start again at any point. 

Partition Walls 

Lime render sticks very nicely to concrete block walls. But things are a little trickier when using stud partitioning. Initially I tried making "lathes" out of thin ply wood. But they were too bendy and it did not work very well. 

Secondly I tried thin plywood with lots and lots of holes drilled in it. This was OK. I think the problem was that I was trying to do everything in one coat (which is easy on concrete blocks), but not so easy on any type of plywood. 

I would recommend using thin plywood, with holes drilled in it . .  ort thin plywood with a sheet of EML over the top. I would then put a thin coat of lime render over this using a notch trowel. Leave it for a few weeks, and then put the top coat on. I did n't have time to do it this way, as I had to get back to my real job. 

Corners

Typically one would use angle bead for corners when gypsum plastering. But lime render is so workable you can use a corner towel if you like. It is hard to get the corners dead straights, but they will look reasonably pleasing when down. 

I used a rounded corner trowel for all corners around windows and else where, and found by the end I found it quite easy. 

Colours

There is nothing stopping you from lime washing the rendered wall when it is finshed. You can get natural pigments and mix them with lime and water to make a creamy lime wash, which you then paint on to walls. 

You can use a roller if you like, but the result will be different to a brush. This is very messy and the pigments will stain your floor boards so put down some sheet. 

Keep that bucket of water handy for eye washing. 

In my honest opinion the lime render is best left naked. It almost feels like you are sitting in nature. I used a yellow building sand which results in a beige colour when mixed with white lime. But you can change the lime colour, and the sand colour to give different affects!

Cost

If you can do the work yourself you can expect a very cost effective result. Materials and tools to render 80 m2 of walls cost me around £300. A plaster might charge £300 to plaster 1 small room. 

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