Brick Stitching on Heritage Properties - Lime Mortar ?

[Ivor Windybottom]

The horizontal cracks in your second photo just look like render that's detached and shrunk. It may look OK on the outside, but it's probably just hanging in the air. Which is good news, as it means there's probably no structural issue beneath. But also bad news as it means the render is no longer part of the building. If the render's cracked and the building hasn't then this can only occur if the two aren't attached, probably over a large area.

You should start by chiselling the render off along the cracks. You'll find out for yourself how attached the surroundings are once you start. If it's prone to all coming off then do exactly that - take it all off. Don't go filling a hole if the surroundings are hanging in the air, you'll be wasting your time, it will crack again and look worse than if you'd done nothing. Plus you'll now have a patch of well stuck new render you'll need to get off before doing it all again properly.

A hammer and chisel will tell you a lot more than an internet forum!

 

[^woody^]

It's cracked along a joint. Render cracked like that is typically caused by the wall moving - either thermal or structural movement.

Not age

 

[rideforever]

It's cracked along a joint. Render cracked like that is typically caused by the wall moving - either thermal or structural movement.

Not age

Indeed, it has been slowly growing since I had it more than 20 years, it's just the bay moving in the wall. At the top its a thin section of wall.
So my plan is to hack of render around cracks, repoint 4cm deep if there are any gaps or cracks in the mortar otherwise leave that. Then re-render. And see what happens. the cracks at the top been there before I got it, so fixing them up will make a big difference.
On the inside corners of the bay there are a few hairlines so will do the same internally.

 

[rideforever]

Well ... I did some work on Tuesday, the 2 cracks on the RHS of the window, I opened them up on the left.
The top one big one, I took out about 1.5kg of material and put in Lime Putty. I wanted to make sure real lime mortar was in the deep crack.
There was more hollow render above, but was not moving, but I left that.
Now waiting for 1 week to dry. Under the render, on the crack line about 2" the mortar was crumbling all the way through the wall. But on either side it went through about half, then it was just the render.
Around the window frame was some membrane or felt or something so it was hard to do more than I did without dismantling things.
I just stopped and didn't do too much.

On the second line underneath it was better, mostly just render and I took out about 1/2 kg and filled it with toutpret masonry repair. I wanted to put something solid in.

Unfortunately the chiselling I did made the render on the interior on that side come away from the window frame so I just put some filler on that line as well on the interior. That render is mostly not blown apart from an area on the level of the line.

Exterior : Above the window on the R those 2 lines on the small section of wall must be the origin. The short section of wall has cracked there; and the bay is a bit loose in the wall and that small section seems to have moved a little bit backwards, 0.5cm. I covered all the other cracks in ct1 for the winter.

On the interior on the other side, and adjacent the window, is the boiler cupboard and I put a band of mortar down it aside the wall render just for security.

Anyway ... looking more closely it has worsened this year, and I am slightly concerned.
But because it's lime (1890) it's not easy to know what to do.
I called up 3 lime bricklayers today, left message.
But that "well regarded" builder told me that he would do it in 2 days, and put a section of helicalsteel in resin in the crack line. And I think he does take a lot of care with his work. However that must mean he uses rapid set mortar, and as for steel and resin in a wall from 1890 ?
I thought the whole idea was to use lime because it moves with the wall.

My experience with the bricks here is that using toutpret it adheres so strongly to the bricks that if you try to get it off the surface of the bricks actually tears off. Its very different from lime. This house is pretty old.

I heard about some Metakaolin / lime render that goes off more quickly, wondering if I should use that and continue piece by piece week by week shoring it up until its sound.
That first builder said he has a window in July 2027 ....
Brighton everywhere you go is scaffolding and its October.

Heritage MK Mortar quicker setting ... anybody tried it ?

Cornerstone Heritage MK Medium Mortar and Render | Cornish Lime

Shop Cornerstone Heritage MK Medium Mortar & Render online at Cornish Lime. A high-free lime mortar offering a breathable & porous alternative to hot mix.

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