Matching new mortar (for re-pointing) to old

[adamr7747]

Hi All,

I've just moved into an old building which has a long (~3m) vertical crack (~1-3mm wide) in the gable wall. The surveyor didn't seem to be too worried about it and suggested "informal monitoring". To this end (and to prevent water getting in) I'm thinking about filling the crack with new mortar. I know that I need to avoid cement but am not sure about how to work out exactly what mortar to use. Should I just go to B&Q and get some ready-mix of the shelf? How can I match the colour to the existing mortar?

Thanks a lot,
Adam

 

[Shytalkz]

Seriously: get a builder to do it, you'll make it look like a hog's ear and far worse than the crack looks.

 

[adamr7747]

Really? Builders are expensive! It seems like it should be one of the more straight-forward things on my long list of things to do on this new/old house.

As for aesthetics, the current crack doesn't look too bad - will a filled crack look worse than an empty one? In any case, I'm more concerned about stopping water getting in and being able to see if there's any further movement.

Thanks,
Adam

 

[stuart45]

Adam,
Is is stonework or brickwork? Does the crack go through the bricks/stone or is it in the joints?

 

[adamr7747]

Sorry for the delayed reply.

It's stone (Blue Lias). The crack is almost entirely in the joints, though it does go through two stones.

Thanks,
Adam

Here's piccy, in case it helps:

Untitled

• adamr7747
• 3 Jul 2009
• 1

 

[stuart45]

Adam,
It looks to me like it has been re-pointed before with a cement mortar. To match that colour you might have to add a touch of black cementone to the mix. It's quite common in Somerset for the bricklayers to darken the mortar like this when re-pointing Blue lias stone work.

 

[adamr7747]

Thanks, I'll try that.

I think you're right about the cement (that was also my Dad's opinion when he visited the other day).

Adam

 

[^woody^]

Fill it with clear silicone, and move than netting across to hide it with that plant

 

[adamr7747]

Hmm, I'm struggling to reach a conclusion about this. I was settled on buying some lime mortar online and using that (& maybe investigating some dye to mix in) but then I talked to my nearest lime-supplying company...

The guy pointed out that as the lime mortar is more porous than the surrounding cement, I could end up with water getting in through the lime and then getting struck behind the cement

So, short of re-pointing the entire wall (which is not going to happen!), I guess I should use a cement mortar. But that leads to the next question:

• - What mix should I use to ensure the cement mortar is weak enough to avoid pulling the stones apart like the existing stuff?

Any thoughts/advice greatly appreciated.

Thanks,
Adam

 

[onebobo]

Hi Adam.
I have repointed a few stone houses over the years and have just finished an old cottage i own.
I found that 6 sand,1 cement and 1 lime and darkened with some soot (experimental as to how much) did the job without looking new.