Housing - Renovation: Wrong type of mortar used - suggestions?

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- CommentAuthorsuperfurry
- CommentTimeMar 22nd 2021
Hello all. Wondering what to do and would appreciate some advice. We have a 1901 property with a rear extension which looks original but might have been built a little later. Anyway the parapet wall facing our neighbours side needed some localised repointing at the top - a 5 course of bricks from one end to the other. It is a south facing exposed wall and I expect this top section was getting the worst of the elements as the mortar had failed. Anyhow to cut a long story short the repointing was carried out last week in cement based mortar in a weather struck style. I was told this was to match the existing wall pointing which he told me was done in cement (I think this is true as others have confirmed). Anyway, since then I read up about how lime should have been used to replace. I am wondering if I should have him redo it. The only thing is he needs to work on my neighbours side - they also keep bees - and have already endured two days of disruption when the original job was carried out on a scaffold. I am also wondering if trying to remove it now will do more harm than good as I expect its hardened up and not weakened over years like the previous mortar so will be tough to remove. Just been reading so much stuff on the heritage sites about the devil of cement it has made me really anxious.
- CommentAuthortony
- CommentTimeMar 22nd 2021
Pragmatic approach now would be to leave it and hope for no problems - you would have to pay and likely do more harm than good. Would have been a better idea to have used lime.
- CommentAuthorrevor
- CommentTimeMar 22nd 2021
Agree with Tony best leave alone now. For anyone else contemplating repointing many years ago I had my previous house a late Victorian semi repointed and that was done with a lime cement mortar. The builder had a cement works make up a lime sand mix tinted with the correct shade of black to match the original. The mix came bagged and was mixed on site with cement added (forgotten ratio) It worked out very well. I sometimes visit my ex next door neighbour and now 29 years later it still looks same colour. A neighbour had their house repointed the owner was a quantity surveyor (and should have known better) had his house pointed with a sand cement mix and powdered dye added on site. It looked great for a while but then started fading after a few months until it looked a real patchy mess of greys. I think the lime plays a part in fixing the dye i.e. acts as a mordant much like an additive in cloth dyeing works. End of lesson!!.
- CommentAuthorsuperfurry
- CommentTimeMar 22nd 2021
Thanks both. It has opened my eyes to lime for sure. What is interesting is that I spoke to the chap today. He said where he repointed the existing sand and cement joints were unusually wide - 20-25mm when they should be more like 10mm. He thinks the parapet wall was rebuilt at some stage as he didn't think the original victorian build would have had such oversized and irregular joints. I got the feeling he didn't think a softer lime would work in joints that wide and the wall section would need a complete rebuild to create more appropriate size joints for lime pointing. He said he sprayed the bricks and joints with waterproofer. So fingers crossed it won't be a complete disaster. Revor interesting you said you used a lime/cement mix. I read people who say that adding any cement at all to the lime mix basically cancels out all the soft and breathable properties of lime. I am glad it worked so well for you though.
- CommentAuthorArtiglio
- CommentTimeMar 23rd 2021
Iâ€™ve a building built 1870, in what would have been a well to do area at the time, the idea that the builders of olde were incredibly skilled and diligent in what they did would be dispelled as soon as you see the brickwork. Looks fine at a quick glance but the mortar joints vary from a couple of mm to 20ish. Pretty much seems they only really levelled it up every so often , usually where it was needed for cills or lintels.
- CommentAuthorChrisinYorkshire
- CommentTimeMar 23rd 2021 edited
I went about repointing the front of our 200+ year old sandstone cottage last summer, after getting fed up with the amount of freeze/thaw damage. It had big chunky cement strap pointing all over it (like many houses in West Yorkshire).

I realised quite quickly that at some point a large section of the wall had been taken down and rebuilt as a cavity wall. There were gaping chasms between some of the stones, they'd really stretched the joints and it had been rebuilt with a very hard sand/cement mixture. This meant endless days chipping it back to a reasonable depth to take new lime mortar.

The solution to wide joints for lime pointing is stone pinnings, in our case I made hundreds of small sandstone pinnings which I pressed into an initial layer of lime mortar and then pushed additional lime mortar over the top.

Time will tell whether it helps evaporate moisture from the wall!

I'll try and upload some photos.
- CommentAuthorChrisinYorkshire
- CommentTimeMar 23rd 2021 edited
Before
- CommentAuthorChrisinYorkshire
- CommentTimeMar 23rd 2021 edited
After (but still wet to aid curing of the mortar, NHL3.5)
- CommentAuthorDominic Cooney
- CommentTimeMar 23rd 2021
Beautiful job. Some parts of our house are like that - the bits that have been easy to get to by previous owners.
The more inaccessible parts haven't been ruined! Its on the list to chop it all out and repoint with lime, but its very low down on the list... below fixing roof leaks and insulating everywhere!
- CommentAuthorkristeva
- CommentTimeMar 23rd 2021
Posted By: ChrisinYorkshireAfter (but still wet to aid curing of the mortar, NHL3.5)
Nice work Chris.
- CommentAuthorkristeva
- CommentTimeMar 23rd 2021 edited
Large swaths of my house have been repointed with cement render, it was picked up by the surveyor straight away. Like Dominic its low down on my list of priorities behind roofs, bathrooms, kitchens, etc, but I can't wait to get out there and start! Unlike Dominic however the high up inaccessible parts are just as affected as the rest so I'll be borrowing my mates scaffolding.

I'm quite fortunate as I live 30 mins from the Lime Centre in Winchester, I sent them a sample of the original mortar and they matched it for strength and colour (soft-medium). My house is built on clay so it moves a lot through the seasons as the ground heaves and contracts I guess. I started off doing interior repairs, etc, there were quite a few holes where the house had been altered over the years and the usual rubble falling away under window sills, etc. Over the months I've got quite proficient at it - knocking up and application - which is probably good if you're going to tackle the exterior where appearances matter!

The walls to the Oast house are particularly bad and in need of repair, I can see evidence of the dampness / salts in the lime plaster.
- CommentAuthorkristeva
- CommentTimeMar 23rd 2021
Posted By: ChrisinYorkshireI went about repointing the front of our 200+ year old sandstone cottage last summer, after getting fed up with the amount of freeze/thaw damage. It had big chunky cement strap pointing all over it (like many houses in West Yorkshire).

I realised quite quickly that at some point a large section of the wall had been taken down and rebuilt as a cavity wall. There were gaping chasms between some of the stones, they'd really stretched the joints and it had been rebuilt with a very hard sand/cement mixture. This meant endless days chipping it back to a reasonable depth to take new lime mortar.

The solution to wide joints for lime pointing is stone pinnings, in our case I made hundreds of small sandstone pinnings which I pressed into an initial layer of lime mortar and then pushed additional lime mortar over the top.

Time will tell whether it helps evaporate moisture from the wall!

I'll try and upload some photos.

Just a few questions Chris if I may?

What did you use to chip away the cement. I'm guessing it wasn't easy?

And have you tackled any spalding bricks yet? If so, how easy were they to remove whole and turn around?

Cheers
- CommentAuthorChrisinYorkshire
- CommentTimeMar 23rd 2021 edited
I used a plugging chisel and a lump hammer to begin with.
Where the stone had receded the strap pointing came off easily, it's just surface pointing and barely plugs the joint.

The problem was the strong bedding mortar being cement based, which I hadn't expected. That meant an SDS mortar raking chisel, tungsten tipped. If you're careful with an SDS (lightweight) you can minimise damage to the stone. Obviously the width of the joints comes into effect

The photo below shows the joint raked out to a reasonable depth.. I also removed as much of the mortar that you can see stuck to the inner faces (top and bottom) as I could. The SDS was useful for this...

I haven't removed any large stones as such on this wall. However I have on an internal wall, where they were loosly bedded in haired lime or even mud/clay. That was easy, but quite different from brick work I'd imagine...
- CommentAuthorsuperfurry
- CommentTimeMar 23rd 2021
Posted By: ChrisinYorkshireI went about repointing the front of our 200+ year old sandstone cottage last summer, after getting fed up with the amount of freeze/thaw damage. It had big chunky cement strap pointing all over it (like many houses in West Yorkshire).

I realised quite quickly that at some point a large section of the wall had been taken down and rebuilt as a cavity wall. There were gaping chasms between some of the stones, they'd really stretched the joints and it had been rebuilt with a very hard sand/cement mixture. This meant endless days chipping it back to a reasonable depth to take new lime mortar.

The solution to wide joints for lime pointing is stone pinnings, in our case I made hundreds of small sandstone pinnings which I pressed into an initial layer of lime mortar and then pushed additional lime mortar over the top.

Time will tell whether it helps evaporate moisture from the wall!

I'll try and upload some photos.

Chris that really is a fantastic job you have done there. What a labour of love. You would be in high demand in London where most of the brickies don't want to work in lime it seems!! I find it very interesting how the 'state of the art' in many respects gets rolled back on to the old ways which turned out to be better. I read somewhere that in France of all places during the cement mortar boom all their historic buildings were repointed in the stuff too. Around here lots of Victorian terraces have been repointed - in fact there are patches of different colour pointing all over many houses if you look closely enough. I expect a lot of the new pointing is cement. I do find it hard to tell though - still not got a real eye for lime although I know it is generally a more off white colour.
- CommentAuthorsuperfurry
- CommentTimeMar 23rd 2021
Posted By: Dominic CooneyBeautiful job. Some parts of our house are like that - the bits that have been easy to get to by previous owners.
The more inaccessible parts haven't been ruined! Its on the list to chop it all out and repoint with lime, but its very low down on the list... below fixing roof leaks and insulating everywhere!

Dominic - I think I have been a somewhat naÃ¯ve homeowner in that I always thought when problems arose I would have the means (financial and mental) to get them sorted straight away. I am now starting to realise that as a historic homeowner (1901 built) I can't do that as there is always something to do and more stuff revealing itself as you do the other stuff. Along with the possibility that addressing something could actually be even more detrimental than what you are trying to fix. For example we had that patch repointed on the parapet wall where the mortar was failing and covered in moss. Then I realised that all these years the area has been getting wetter than perhaps it should due to the coping stone not having quite enough width on the wall side for all the rain to run off effectively. Luckily not noticed any damp ingress in the almost 8 years we have been here, and all repointed and sprayed with waterproofer now but something to add to the list of issues to think about taking on along with everything else we have going on....A builder said to us that removing the coping stones from the parapet wall of that age could cause some pretty serious damage and we might be better leaving it. Thinking of a way to extend the coping stone without actually ripping it off....
- CommentAuthorrevor
- CommentTimeMar 24th 2021
A mortar pick is a very useful tool once you have got through the top hard bit of mortar by other means. There are other ways other than SDS chiselling an angle grinder with a carbide or diamond "router" type bit is very useful a disc is prone to cause damage so best avoided.
- CommentAuthorDominic Cooney
- CommentTimeMar 24th 2021
Posted By: revorA mortar pick is a very useful tool

We still have one that SWMBO used when she chipped out all the mortar and repointed the last place. I reground it to a sharper point a few times, its now worn down so short we call it the "Shawshank"

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