Front of house render material?

[bmartinlevy]

Hi everyone, was hoping someone may be able to help.

We've been trying to figure out what material the render on the front of our house is made out of (image included below). It's an 1862 Victorian terraced house--most information we could get from the neighbours is that the render has been there since pre-WW2 and has been painted over several times (they thought it was just painted over brick but really looks like render to us?). We've stripped back the inside of the house to brick and are hopefully plastering the inside in lime plaster. We are a bit concerned in using lime plaster on the inside if the outside is covered in cement render, as seems like a lost cause and don't currently have funds enough to tackle the front if it is an unbreathable material. It has been painted over unfortunately at least 2 times as well (once with Dulux we found in the cellar when moving in). We are removing the skirting at the bottom which are covering air bricks at least.

Any advice would be appreciated!

 

[Cubist]

Hi Martin and welcome,

Before making a decision as to whether the render is lime or cement its probably wise to look at the paint first as this is most likely to be an impermeable barrier that prevents the house breathing. You say the previous owner left a can of the paint used so you should be able to find out whether it provides a water-proof coating? If it does, then whatever the material below it may be it will not be able to breathe and therefore moisture produced inside the property will not be able to escape through the rendered walls even if the render is a lime mortar. Moisture trapped near the outer surface of the bricks and near the interface with the render material can result in 'blown' render or brick surfaces after repeated freezing and thawing - is there any evidence of loose patches of render or exposed bricks that have been damaged? One way to test for such is to gently tap the surface of the render with a piece of wood whilst listening for any 'hollow' sounds. If you find any its almost certain that the brick face and the render have parted company. On the other hand if you don't find any obviously hollow areas then the render, and its bond to the wall, is probably good, and provided there is no evidence of damp on/in the interior walls, then you have dodged the real bullet and get away with just re-painting the render.

The worst case would be to strip off all the render to get rid of the paint

Hope this help.

 

[malcolm]

Render before WW1 was normally lime. After WW2 normally cement. In-between could be either. If a light tap with a hammer feels soft and there aren't lots of cracks in the render it might be lime.

My upper floor was rendered in 1921 in cement annoyingly. It has since been painted in masonry paint which to all intents and purposes is waterproof. Being an upper floor it hasn't caused problems so the render and paint is still there and I've painted over it with pozilime lime wash which has lasted well.

For plastering directly to internal walls lime is the answer whatever the exterior covering. The modern approach of completely waterproofing walls on both sides doesn't work. The wall gets really wet and goes mouldy like the pub down the road.They have renovated that twice in the last 10 years as the walls keep going mouldy. To me that's a sign that the walls are soaking wet and cold and attracting condensation.

 

[ElectronicFur]

I you have any exposed render then just try the vinegar test, add a bit of vinegar, and if it fizzes you know it's lime.

Even if it is cement, it's not ideal, but not necessarily disastrous. Our house has been rendered outside in cement and painted with modern paints by the previous owners since 1984, and it's still fine. Inside walls are still all lime.