Cement pointing damages stone - perfect example

[@deribrown]

great example made there. the cement pointing was probably done with the best intentions however time has shown the damage. as a builder myself I have been guilty of doing this sort of thing as a young apprentice many years ago, however as I educated myself in the ways of older building methods I always advise my customers to repair old buildings in the same manner as they were originally built and now I am moving over to working on preserving older buildings. it's a shame more builders are not able to educate themselves better.

[@pdbay47]

I'm sure many of us have stone walls which have been cement pointed in this way. It's what builders do, and they are very reluctant to change their ways. My question is "what is the best remedial action, given this situation, and what sort of ball-park cost per square metre (or yard) would we be talking about?"

[@WarmDryHome]

Ballpark - we use a figure of about £90 / m2 - but so hard - stone can be very variable in size - so one house may be very quick to do, another takes a long time.

[@pdbay47]

Thanks for that. I need to do it piecemeal.

[@gleff3345]

Thanks for another informative film. Just finished removing loads of sand and rubble from my cavity wall. Hope this helps against the dampness!

[@WarmDryHome]

Me too - you should really have recourse against CIGA - they are legally obliged to fix the mess..

[@dismaldog]

great display video-i actually cringe now when i see old masonry re-pointed in cement or even old brickwork or tuck pointing painted with modern plastic paints.

[@WarmDryHome]

Yup - and how many builders do you know who take the time to study and learn this stuff???? Not many I'll bet..

[@vinceking7878]

I don't understand how stones can get ruined

[@belgianquill]

Does this apply to cement pointing on old London brick?

[@WarmDryHome]

It sure does.. that's why so much of the brickwork is spalling. It also means that the walls get damp because moisture can't get out - hence the damp industry and their stupid injection holes. Totally not needed! Just remove the cement, let wall dry out, and re-point in lime.

[@felixyusupov7299]

I have to repoint my exterior red sandstone. The house has a ribbon style strap pointing. I was going to use Sakrete type N mortar mix to do the repointing. I'm investigating if that is a lime mortar or cement mortar. Any input would be appreciated.

[@WarmDryHome]

Don't go near it - it's just portland cement. Lime pointing is REALLY simple - 3 parts sharp gritty sand, 1 part lime - we use different limes these days - a soft NHL - a 2.5 (NHL stands for natural hydraulic lime - NOT hydrated lime sold by builders merchants..) Or you can buy pre-mixed from places like Ty Mawr lime. The industry is now moving towards pure putty mixes or hotlime mixes - they are even softer and more breathable. DO NOT use anything with portland cement or additives - it must be just plain lime and gritty sand. You would be advised to do a lime pointing course at Ty Mawr - then you'd fully understand what you are doing and how - its very easy and simple to do, but you CAN get it wrong, and I'd hate for that to happen when you have the best of intentions! Using anything with portland cement in it will just carry on the destruction of your sandstone walls.

[@felixyusupov7299]

Thanks! I found this outfit. I think they can supply what I need domestically: www.lancasterlimeworks.com/products-info/lime-mortar-mix-for-repointing-2/

[@WarmDryHome]

Looks good to me! Good luck :-)

[@KevinAmatt]

Apparently hydraulic lime is just a bad as cement. Cracking the stone due to expansion of the joints.

[@WarmDryHome]

Kevin I'm not sure where this comes from - it does not expand, and it allows breathability. Even an NHL 5 is about 100 times more breathable than cement...

[@KevinAmatt]

Peter, I got that information from Carole Ryan's book: 'Traditional Construction for a Sustainable Future'. If you think NHL is 100 times more breathable than cement, what evidence do have? Where did that come from?

[@KevinAmatt]

It's in the chapter 'The Pathology of Traditional Buildings' page 324.

[@FinnsEpicVidz]

Peter, informative video. What would the detail to remedy if a house has cement strap pointing, would I reinstate as strap pointing style but in lime? The property next door also have strap pointing, and i was think for continuity to keep the same. Thanks

[@WarmDryHome]

Hi.. It needs raking out to a depth roughly equivalent to 2.5 times the joint width. NOT with angle grinders which irreparably damage the stone / brick. You CAN use the arbortech masonry saw with a 6mm heritage blade.. Lime should be a matched mortar - try to come up with something similar to what was there before. Ideally you use a hot lime mix, or slaked lime in a 3:1 mix - where 3 coarse, gritty sharp sand, and 1 quicklime, mixed to a putty consistency - will take about half hour to mix, and dont get too wet. Nowhere near as wet as cement. Alternatively you could use NHL 2.5 hydraulic lime - (NOT hydrated builders lime which is just a plasticising chemical for cement) - again a 3:1 mix with the NHL will work. Bang into the joints with a stiff brush, and brush off - you dont want a horrible flat, tooled finish - the old boys rarely did that unless very fancy brickwork. Lime from Ty Mawr or similar lime suppliers. Note that we are starting to move AWAY from using NHL limes - to using hot lime / quick lime mixes, as they are more breathable and fill the joints better when pointing.

[@tompiccirilli7987]

Hi, Thanks for your very helpful videos, I'm having a few worrys with our new house which is built from stone and 100+ years old and unfortunately rendered outside and inside, we had a few patches of blown plaster and salt coming through which was due to cracks on the outside render, I stripped back to bare stone on the interior wall and applied some salt neutraliser or antisulphate before re rendering but after a few days I noticed some spalling appearing on the stones, the stones where in good condition before but after I applied this antisulphate is caused the stones to spall, the patch is 1m square. I'm a little worried about it and wanted to know of it was anything to worry about? Cheers

[@WarmDryHome]

Hard to say without seeing it. I'd not use any chemicals - no need. Scrub down, remove any chemicals, leave to dry. Then re-point using a soft lime mortar...

[@tompiccirilli7987]

Thanks for your reply, really appreciate the help. Do you think the mild spalling is anything to worry about or will the stone still be ok? Cheers

[@julianround4893]

Hi Peter, thanks for your video's - I've watched the lot! This question is from the other side of the globe, Hobart, Australia. I recently purchased an 1899 built weatherboard home in the 'Federation' Edwardian style of build, common to the area. The house sits on a combination stone foundation (internal walls are bluestone and external wall facing the outside world is sandstone). The block is approx 15% decline. At some point in the 50s or 60s, a sunroom was added which is on a large concrete slab. At this point they have painted the concrete and thinly rendered then painted the stone foundation too (so to create continuity in the look- and it does work from a visual perspective). After watching your videos I am wondering if this is healthy for the sandstone? Keeping in mind the crawl space sides remain exposed and natural, appear very dry and the ventilation is good under the house. So much so I feel a slight draft when I'm in the crawl space. If you are curious to see images, I can email to you. + there is no bulging paint, It remains intact and appears to have been so for decades.

[@WarmDryHome]

Spent 24 years in Perth, so know the Ozzie conditions - although Tassie is cooler and wetter.. You are right in all you say - ideally paint should allow sandstone to breathe - but if there are no problems, I wouldnt make too much of a fuss. If you got paint off and replaced with limewash, or one of the silicate based breathable paints from Keim - not sure if you have them over there - it would be even better. Maintain good ventilation under the crawl space - if that is good, you should have very few problems. I could almost walk around under mine - biggest issue was termites!

[@julianround4893]

Peter Ward Thanks Peter. I investigated further and discovered what I thought was sandstone is actually an old 1inch thick concrete render over the foundation stones. I removed a portion and behind were stones with what I'm assuming is a local mortar mix. The mortar was so wet I could pull it out with my fingers. I've since removed about one square metre of concrete exposing around 7 or 8 stones. They quickly became a different colour in the afternoon sun. I'm going to continue removing the concrete which I estimate is circa 1950s or 60s. I'm also going to create more crawl space vents in the bottom weatherboard (the joists are at this level) as I could see one of the rooms towards the rear of the house where the block levels off has evidence of moisture in the wood. You can see the moisture line half way up the joists. The joists have been sistered as the original 1900 wood has bowed however it does not look in any way rotten. The house is luck it is built on a nice gradient slope giving it a large crawl space at the front and enough ventilation to avoid what I've seen in your videos! There is a lot of lovely original lath and plaster which I'd like to protect. Only question I have is will I cause structural issues removing the render. I'm guessing I won't as it is not load bearing. Some nice features like 1 foot wide Victorian style cornices I'd like to not disturb. Thanks for your replay. I've found suppliers for lime based mortar in Hobart (not Bunnings lol). Planning to re point as required once the wall is dry. also the concrete only requires a light tap with a hammer and chisel wedged between the stone and render to dislodge. Very granular mix in the concrete. Thankfully coming off easy.

[@WarmDryHome]

No - removing render will be fine - as you say, let it dry out underneath - just make sure the mortar is ok - might need to rake and repoint in lime - I think you should be able to get NHL lime - its called natural hydraulic lime (not the hydrated lime in builders yards) and mix 3 sharp gritty sand with 1 lime... nice and dry like plasticene and push into joints - brush off and let dry - but keep damp for a week or two ata least so it carbonates.. Just read on - yep - avoid bunnings !!! Keep us posted - be good to see an antipodean example on the webiste - [e-mail] !!! Have a great Xmas!

[@julianround4893]

Thank you sir. Very helpful.

[@gigs000]

Great videos, keep it up!

[@WarmDryHome]

Thanks - we try - hard work keeping up!

[@JamesJones-jy8vs]

Have the stones been damaged beyond all hope, or have they just lost a veneer and once pointed with the proper stuff will be ok. I have an old house which has been subjected to ignorant builders, and that's exactly what's happening to mine.Thanks for the enlightenment!

[@WarmDryHome]

Not beyond hope - just a bit tender. They need re-pointing in a soft lime render and should be ok now - but what a pity.. Just remove any spalled material and point in a soft lime..

[@dbcleaningservices]

Great video thx