Blown render - remove and paint wall directly?

[Tony Jackson]

OK, here's the story: :)

We have a house that is stone built on three walls, and brick built on the rear wall (solid 9" jobbie, south facing).

The previous owners saw fit to built the most hideous extension known to mankind, and then render it along with the brick rear wall.

This house is 1930s ish and built with lime mortar. Clearly the guys that rendered the extension and rear wall didn't have the word "lime" in their dictionary as it's now pretty much all blown and cracked.

Now, with any other house I would expect the bricks under the blown render to be shot as well. However, the bricks used in this wall are all nearly as hard as engineering bricks. They're that hard that hammer drills won't touch them and SDS is the only way.

Now, due to exception levels of no-money-at-all for the forseeable future, there is no way we can afford to have the wall re-rendered.

I've been thinking about either:

a) Drilling it all over and injecting gripfil or latex self-levelling compound etc (whatever will stick the render back onto the wall)

b) Removing all the old render myself and painting the wall directly.

Currently b) is my preferred option because I believe the bricks will be OK under the blown render.

Would this be a big mistake?

Please advise. :)

[Mike]

Yes. Paint it with limewash temporarily but render it with a lime render gradually as time permits.

[N. Thornton]

Any cracks at all in render will let water in but not let it evaporate out, so this is not an option.

b should be fine, if the bricks are mostly in one piece, and you make sure the pointings ok. But better would be let the render fall off and dont paint the bricks. If theres render on them, as there will be, knock the lumps off, gently enough to not break any bricks, wire brush whats left down to 1mm or so, (rotary brush in angle grinder) then use brick acid to remove what remains. Yes its extra work, but it will look miles better, perform better damp-wise, need far less maintenance than paint, and since its only cosmetic work there's no rush to do it.

In fact, if the wall underneath is ok, theres no rush to do anything at all, just a matter of cosmetics.

BTW your other option is to remove loose render and rernder in lime, but I wouldnt myself, unless I was desperate for time.

If OTOH the wall underneath is structurally precarious, eg the bricks are badly disintegrated, it may be necessary to rerender.

NT

[Tony Jackson]

I think I will do as you suggest - let most of the render fall off and then remove the rest, clean the bricks and re-point (assuming the bricks are in good condition - but they are very hard in that wall). At the moment we have damp penetration due to the blown render trapping water against the wall. I assume with bare brick and proper pointing this will cease?

Thanks for your advice, anyway.

Tony

[N. Thornton]

In nearly all cases, yes. If its a weak 4" thick wall though, I would be less sure. Even if the bricks are not in perfect condition, if there arent too many broken they can generally be repaired in situ by drilling a few small holes into the crack and injecting resin. In some cases its also an option to cut them in half in situ, and mortar them just like 2 smaller bricks.

The only caution is that if there are substantial structural problems with the wall, such as gross mortar loss, it might be wise to repoint in patches, only removing small areas of render at a time before pointing them.

Theoretically, and more than unlikely, if it were a 2.5" brick wall supporting 3 stories, it might be in real need of a thick coat of render. I've never seen such a thing in the real world though, or even heard of it.

NT

[tony.jackson]

Pleased to hear that. :)

Thankfully the wall in question is 9" (not including plaster/render).

wall (to run through waste pipe), the mortar appears to be in good condition too.

Will continuing damp in the wall (while the render stays up) make the lime mortar deteriorate?

[bigcat]

yes, it makes everything deteriorate. Freezing is what does the most damage. But its not as if a week would make a significant difference one way or another.

One could go round with a hammer and tap the loose lumps off. The wall will take quite a while to dry out.

NT

[bigcat]

yes, it makes everything deteriorate. Freezing is what does the most damage. But its not as if a week would make a significant difference one way or another.

One could go round with a hammer and tap the loose lumps off. The wall will take quite a while to dry out. An SDS would work well too, but if using one dont go too mad, dont want to break up the wall behind the render :)

NT

[bigcat]

yes, it makes everything deteriorate. Freezing is what does the most damage. But its not as if a week would make a significant difference one way or another.

One could go round with a hammer and tap the loose lumps off. The wall will take quite a while to dry out. An SDS would work well too, but if using one dont go too mad, dont want to break up the wall behind the render :)

NT