Frost damaged pointing

[Carol]

Our new walling has suffered badly under the recent freeze. Much of the surface of the pointing has come away and the rest seems crumbly to the touch. How much will have to be raked back? It was done in the autumn and had about eight weeks before the temperature dropped. My builder has already said they will sort it but I am interested to know if this will compromise the long term future of the walls. Has anyone else had this problem recently?

My neighbour whose builder is of the "I'll just add a handful of cement dear, to make it last" species has not had the same problem. Which is very annoying as I was trying to convert her to the niceties of lime.

PS Builder is experienced and I am sure his mix was not the problem... I think!

 

[MdB]

The idea of lime pointing is that the water ends up in lime rather than in the stone/brick so that when a frost appears, the lime suffers rather than the stone/brick. Consider the lime sacrificial in this respect. The cement in your neighbours pointing will cause the moisture to end up in the stone/bricks causing them to fail rather than the pointing. Your walls will be better off in the long term.

I'm not an expert on this but it appears that 8 weeks isn't long enough for the carbonation to give the lime enough strength to survive the frosts. It might also be worth considering using a weak hydraulic lime next time so as to give it a bit extra strength.

 

[masochists-r-us]

Please can someone elaborate on the 'handful of cement dear' comment. We recently had some repair and repointing done to our stone garden wall and our man said that just a capful of cement would make the lime mix go off more quickly which my husband accepted.
Have we committed the cardinal sin and if so should we insist on no cement whatsoever in future ?

 

[Inspector John]

Our new walling has suffered badly under the recent freeze. Much of the surface of the pointing has come away and the rest seems crumbly to the touch. How much will have to be raked back? It was done in the autumn and had about eight weeks before the temperature dropped. My builder has already said they will sort it but I am interested to know if this will compromise the long term future of the walls. Has anyone else had this problem recently?

My neighbour whose builder is of the "I'll just add a handful of cement dear, to make it last" species has not had the same problem. Which is very annoying as I was trying to convert her to the niceties of lime.

PS Builder is experienced and I am sure his mix was not the problem... I think!

I pointed stonework on a house before we had the constant heavy rain in November and the recent hard frost (lowest was -9c for our area.) Since then I returned two days ago to inspect, and expecting some of the pointing to have blown but I was pleased to see it was still intact also the dubbing on the rear wall which was laid about the same time had not been affected (Lucky I guess)
On the one hand I'd rake out the whole lot and start again on the other hand if the lime pointing that has not been damaged and has bonded well to the masonry and is still very sound then It's may well be ok to just to make repairs

 

[worms]

Our new walling has suffered badly under the recent freeze.

I pointed stonework on a house before we had the constant heavy rain in November and the recent hard frost (lowest was -9c for our area.) Since then I returned two days ago to inspect, and expecting some of the pointing to have blown but I was pleased to see it was still intact also the dubbing on the rear wall which was laid about the same time had not been affected (Lucky I guess)

Wonder if Carol's post refers to her garden wall which she has mentioned before? A house wall would presumably not be as cold as a garden wall and might have not been frosted at all.

 

[MdB]

If it cheers you all up, my neighbours new concrete slab has frost damage all across the top....

 

[Penners]

Tut tut, MdB.

Schadenfreude. :shock:

 

[biffvernon]

Please can someone elaborate on the 'handful of cement dear' comment. We recently had some repair and repointing done to our stone garden wall and our man said that just a capful of cement would make the lime mix go off more quickly which my husband accepted.
Have we committed the cardinal sin and if so should we insist on no cement whatsoever in future ?

He's right to say that the cement will make it go off quicker but that might not be a good thing. There is evidence that a mix with a little cement is actually less long lasting. No cement whatsoever is better.

Somewhat tangentially, I was talking to someone from Bristol today who said that he had noticed a great deal of dust and bigger lumps of buildings lying on the pavements below buildings. It was very noticeable when the pavements were covered with snow. All along all the city centre roads there was a line of debris. A hundred years of winters like this and there won't be much left of the buildings, he said. Anyone else noticed this?

 

[Carol]

Wonder if Carol's post refers to her garden wall which she has mentioned before?

Yes, it's our long planned and awaited garden wall. Luckily the main part, done first in October is least affected. Worst is the wall between us and the neighbour which will need raking and re-pointing.

 

[mm289]

Exact same issue for us but on the house wall. We have removed a concrete plinth on the front as the wall (concrete rendered above) was soaking. As a result found how badly the injected dpc 25 years ago had damaged the brickwork. Also found complete lack of mortar in the bottom courses of brick (replaced by soil - I guess from insects etc) upto a full brick depth.

Repointed/repaired the worst bits late in Oct/Nov hoping it would dry out sufficiently, but with all the wet weather and then the snow it hasn't. As a result the pointing has blown in places.

Will this cold have damaged the mortar in the wall? It was the devils own job pushing/ramming the mortar all the way to the back of the bricks :twisted: having scrapped out the soil, don't fancy doing that again! :shock:

Cheers,

Paul.

 

[MdB]

What type of lime did you use? NHL or putty / hydrate?

The bottom section of my external pointing has never dried as our ground is just too damp and hence the putty lime has never set. I will need to replace it with NHL at some point.

If the inside of the house was heated, I would have thought that most of your wall would be well above freezing and hence no damage.

 

[still_adrianth]

Frost got pointing in my garden wall too. Mortar was putty+sand, often almost pointing a full brick depth. Stuff I did last spring is fine, but even parts I did in August have blown.

Might this be a surface effect, and now unset lime further back in the joint will get a chance at setting if it doesn't wash out first?

Dismayed, I too have been thinking of NHL for the next bit. But the technical guides say you're supposed to use up a whole bag within a few days of first opening it! No way I can work that fast. I found a site where Mike Wye suggested mixing putty+sand mortar that you can store for ages, then adding pozzolan as you knock-up small quantities for immediate use. Seems the ideal solution for small works? Searching lime suppliers suggests that they all used to sell "Metastar" for this, but have switched to "Argical M1000".

Does anyone know if a general builders' merchant that sells lime putty is likely to have even heard of Argical M1000, or is it a mail order job?

http://www.heritagelime.com/mikemetastar.htm

Sympathy to all, but I feel better knowing I'm not the only one!

Adrian.

 

[still_adrianth]

Please can someone elaborate on the 'handful of cement dear' comment. We recently had some repair and repointing done to our stone garden wall and our man said that just a capful of cement would make the lime mix go off more quickly which my husband accepted.
Have we committed the cardinal sin and if so should we insist on no cement whatsoever in future ?

English Heritage's Smeaton Project did a lot of tests to get to the bottom of this. One summary is http://www.buildingconservation.com/articles/cement/cement.htm. My reading is that if you add a small amount of cement (eg. just enough to get a quick set) the cement is likely to segregate from the lime during setting leading to a weaker mortar; that to avoid segregation a high proportion of cement is needed, defeating much of the point of using lime in the first place.