Removal of cement in old window opening

[KarlB]

Please say this is worth the effort? Currently removing cement render from one of the 3 rendered walls of the house and have just discovered a filled in window (with cement). The brickwork is already not looking the best for keeping exposed and this has further pushed me towards thinking rerender in lime is the only way.

Wondering whether I need to go to the effort of removing the cement in the old window opening and rebuilding the wall up to meet the new window size or if I just have to live with that bit of wall not breathing like the rest. Thoughts?

 

[malcolm]

That's worth the effort. Cement render and waterproof masonry paint aren't good for a building. If you are planning to re-render with lime I would leave the cement infill and just render over it. It shouldn't cause too many problems halfway up a wall. If you are planning a brick finish then the cement would look ugly.

 

[KarlB]

We've been told that a bag rub finish might be a good option and allow us to do the pointing and rendering in one go

 

[malcolm]

Walls breathe through the pointing not the bricks. It's worth chipping out any non-breathable cement from the wall before rendering in lime. Any cement pointing is normally done really badly so there should only be a shallow depth to chip out.

I can see a few deep gaps. It would be best to lime point those before rendering just because it's nice to have a structure structural. For gaps less than 3/8 inch any old lime render would fill them up. Bagging tends to be used where a non-flat finish is desirable - stonework and the like. Doesn't sound sensible for a brick wall unless you are even more eccentric than me.

 

[KarlB]

Yeah I will be removing the cement pointing, it's mostly falling out anyway. The original lime mortar flows freely out of the joints though so I'm not sure how to stabilise that/adhere new lime pointing to it as you just keep brushing at it until the bricks come free

 

[malcolm]

Lime does tend to get crumbly when it's been soaking wet for years. I didn't have much on mine where the loose stuff was more than 1/2 inch deep. If yours is worse it might be worth a quick repoint.

 

[KarlB]

Regarding the bag rub finish, to be honest I don't mind what the finish is as long as it breathes. It just sounded like that would allow us to be able to rake out joints and then just apply render without needing to do a separate repointing step. Time and money are both in limited supply and I wanted a cost and time effective way of finishing the walls. I'm struggling at the moment to get any trades people to get back to me on quotes, it's rather annoying. Hopefully I can at least get the windows refit and weather sealed by the winter, not sure if I need to worry about leaving the walls with render removed through the winter, I presume it's better that they breathe, but also the pointing it shite and I don't know if it will cause more water ingress...

 

[aockenden]

I'm struggling at the moment to get any trades people to get back to me on quotes, it's rather annoying.

No way, this absolutely never ever happens... I refuse to believe this...



As for going through the winter with no render and shoddy pointing, on a thinner-walled brick building it is definitely more of a risk for driving-rain pushing water into the joints and through into the house. If you had 2-foot thick stone walls I'd say you'd probably be mostly fine.