Renovating an existing internal brick wall

[Brosharchitects]

I am currently renovating a Victorian terraced property (c 1880's).
We had to expose the brick boundary wall and found out that the existing bricks are in a very poor condition and very badly laid.
We would like to apply dense 'sand and cement' to the walls with mesh reinforcement in order to bond the brick and level the walls.
I was wondering if this is the right way to go about it or should we allow the wall to breathe and have its natural movement.

 

[LadyArowana]

Welcome, can't help with your question, just bumping this up the topic list so it doesn't get lost. New member posts are moderated and can be missed.

 

[Zebra]

It depends on the hardness and porosity of the bricks. The golden rule is that the mortar must not be harder than the bricks, or else it will trap moisture in the bricks, causing them to spall. Cement mortar is the hardest that there is, so I would never use it on anything except modern brickwork. In your situation I would be looking to repoint with lime mortar - again, the choice of mortar depends on the bricks; either NHL or "fat" lime mortar would be the choice - while replacing the very worst of the bricks with similar reclaimed ones, and/or rotating any spalled ones.
Then, to level the walls, use a lime mortar in coat of around 10-15mm thick. A "dubbing out" coat first will take the majority of the unevenness out. To use a cement mortar will only trap damp in the walls and make things worse, I fear.
Do you have any pictures of the affected area?

 

[malcolm]

Don't use cement - it will be a pain to remove when someone has to fix the problems it will cause.

Is it external render on a boundary wall? A lime render would be best, whitewashed not coated with modern masonry paint, and you would be unlikely to need any mesh. Re-point the bricks first if needed (with lime) and sort out structural issues.

Lime has two advantages - it can move around with the building (which will move a bit as it is unlikely to have modern foundations) and won't crack and fall off so readily. It will allow moisture to evaporate from the bricks. Cement does the opposite - it will crack allowing a surprising amount of water into the bricks, but is waterproof so the moisture won't be able to get out again. The bricks will become sodden wet, you get a cold damp house inside and spalling of the bricks in winter frost.

It's not theoretical - it happens in real life. I'm still to replace a timber frame which was good for 300 years before they invented cement to plaster over it.

 

[MatthewC]

Don't use cement

+1

I am currently renovating a Victorian terraced property (c 1880's).
We had to expose the brick boundary wall and found out that the existing bricks are in a very poor condition and very badly laid.

I would ask why is it like this? Was there some non-original plaster over the inside, or non-original render on the outside? Or is the ground level outside higher than the floor inside? There is no point in fixing the perceived problem unless you also tackle the actual original cause of it.

I had some bricks in very poor condition inside because of "cement plaster", and the line of poor bricks followed the line of this plaster exactly. In other words, where the water could not get out, the bricks were fine but, where it could get out through the older lime plaster, a foot or more above the floor, they were very bad (and the plaster was falling off). The fault here was the use of this horrible cement mix as plaster - had they got rid of the high ground outside, and fixed the gutters to stop water pouring down the wall, and then used lime plaster (which is what I have done), it would have been fine (and it is!).

Matthew

 

[plasticpigeon]

A brick boundary wall. This is around the boundary of the property isn't it? How much boundary wall does a terraced house have? Or is this a party wall between two houses. Meshing and cement rendering a party wall seems a bit drastic, it isn't likely to fall down and it would make it a real bugger to change in the future if need be. If in the garden, if it is so bad, why not just rebuild it?

 

[TheRoost]

If it is the party wall you mean, can you elaborate on 'very badly laid' ?

Are the bricks unlevel, sticking out, gappy, untidy mortar? any current damp or signs of previous?

Our party wall (viewed from the loft) is rough and ready with original lime mortar either spilled out, or gaps with no mortar, but it is still solid, and wasn't meant to be seen,so its appearance wasn't a priority when they built it.