Rendering

[JKavanagh]

How hard is it to render an external wall? And how do you do it? I am being charged an extortionate sum for what looks like a very simple job. So..step by step..how do I do it..what do I need and what are worst things to watch out for?

[Quizmonster]

The problem, JK is that any job "looks very simple"...when you watch a tradesman doing it! If you click here, that will link you to a web-page which gives an account by an amateur, like yourself, doing some rendering. Have a look and see what you think.

[andy hughes]

If you think you are being overcharged, get a couple of estimates and compare, or have a chat with a large building firm and see what their subcontractors charge, this will give you an idea. As QM says, a tradesman can make anything look easy. Years ago on 'The Generation Game' they had a man plastering an arch. It loked like a doddle, until the contestants tried it, and their plaster fell off in big lumps. By coinicidence, we had an arch made at the same time, and I watched our man do it, same thing - doddle. I had a go, and looked very silly, and respectful, at the same time. If you are not an expert, pay up and smile, it's not wirh the grief to try it yourself.

[Maude]

The problem with external rendering is cracking and crazing. This is a very serious matter, allowing moisture to enter, make walls damp, looks unsightly, chunks often fall off following frosty weather and sometimes the brickwork beneath is destroyed. The specification that you should follow is (1) cover the external wall with stainless steel expanded metal lathing (XML) well fixed to the wall with stainless nails (2) apply a first coat of cement and sand 1:6 well pushed into the XML and covering it by about 12mm (3) leave the first coat for two or three days and then apply a second coat of cement and sand 1:3 again about 12mm thick finished with a wood float if you want it looking like coarse sandpaper, or a steel float if you want it smooth. Make sure that you finish the rendering up to something that will prevent water getting behind at the top and sides, and form a small bellmouth to act as a drip at the bottom. Leave for 2 or 3 weeks and then apply suitable paint from any well known manufacturer. If you want the very best, apply Keim paintwork. If you follow this specification (either with a contractor or DIY) you will have trouble free rendering, but if you apply any rendering direct to the wall there will be trouble ahead. If you are tempted towards DIY, the secret is that you must lean heavily on the rendering to apply a coat. If it seems a bit sticky, stir in some Fairy Liquid every now and again.

[Maude]

PS. The sand should be sharp sand, not soft. Control the water carefully so that the mix has the consistency of treacle. It is better that the mix should be stiff, and not under any circumstances runny. To finish the top coat properly with a steel or wood float you may first have to wait by the wall for an hour or two until the rendering has passed its first set and is able to take the finish.