Why stone walls spall and erode

[@gilessteve]

Thank you for posting that. It's always nice to see new videos from PW.

[@PaulIreland]

Another great video Pete, keep them coming!!

[@paulied1473]

Awesome video, very informative and to the point haha. Thank you very much

[@TheRestorationCouple]

Very informative, thank you. Had always thought that the flakey layer was just the stone breaking up however it does appear to be gypsum on our stonework as you have pointed out. We need to remove cement pointing in a similar way this year, looks to be a labour of love! Do you ever recommend blast cleaning stonework? We have a lot of marks and stubbon remains of old creeper and ivy that doesn't seem to shift by scraping or brushing and thought it may be good to blast clean before we repoint with the lime.

[@WarmDryHome]

+The Restoration Couple Blast cleaning can do a lot of damage - we DO do it, but using VERY low pressure - about 30 or 40 psi. There are 2 processes - doff and torq - by a company called stonehealth, that are approved by Historic england - worth asking for a quote but not cheap! Don't use grinders onstone / brick to remove pointing - can use an 'Arbortech' - we use one with the 6mm carbide blades, its brilliant - but pricey - Costs about £1k... :-(

[@JayCWhiteCloud]

Excellent job as usual Pete...I love sharing this with colleagues here "across the pond." Look for ward to more my friend... Cheers, j

[@alper2007]

This video helped me understand what is going on with our stone pillars. Do you know of a sealer that I can use to stop this from happening? I guess we have gypsum on our stonework that crumbles, but we also have actual stone itself flaking/crumbling. I am afraid we will end up losing enough stone that will require replacement. Again, is there a way to waterproof the stone and grout? Thank you.

[@christopherejankins]

What kind of mix should you use to repoint? I think I heard him say lime?

[@WarmDryHome]

yup - ideally, hot lime - a 2:1 or 2.5 : 1 of sharp sand / hot lime mix. You can use NHL 2.5 hydraulic lime (not hydrated from builders yard - thats rubbish) but we find the nhl is a bit hard to allow breathability.

[@KevinAmatt]

When I work on old houses with cement pointing I always advise the owner that it should be removed. The general response is ' The process of removing the cement pointing will damage the stones.'. If it is not removed it's the building that will suffer. I need more information to convince them to change their minds. Also I've had many meetings with conservation officers about cement pointing on listed houses and why they do nothing about it. They say we do not have the power to make the owner remove the pointing or the power to stop them using cement pointing. Well that makes me think they don't care about old buildings.

[@WarmDryHome]

+Kevin Amatt Many CO's simply don't really understand. I think there is a new breed now who do - you should always reference BS7913: 2013 - Guide to the Conservation of Historic Buildings - it's very good, and you can use it in your presentation to CO's - that way you know more than them! The guy who wrote it used to be the Director of Cardiff Castle for CADW - so really knows his stuff, and supervised the restoration of the castle. The issue of 'stopping' people using cement pointing is a sore one - I'm very active within IHBC and I can assure you it raises hackles. What the solution is I don't know - other than better education. Same for the damp wallies and their injection. You will see in BS 7913 that John advises against timber treatment and damp proofing completely, referring to breathability and removal of impervious materials as the solution. I have an IHBC copy of 7913 - nice and laminated.. Not cheap - about £200 - or can give you a pdf preview :-)

[@KevinAmatt]

+Peter Ward Thanks, I've ordered a copy from ebay for £71.

[@WarmDryHome]

+Kevin Amatt Crikey - someone must be copying them... well found! I paid about £240 for mine.. Trying to get them to let it out cheaper.. Keep us posted with progress - any problems, email me [e-mail] and I'll do what I can...

[@TheNixbrix]

not if it is cut-out .....very carefully using a sparky/grinder.....also ..if you ribbon/strap repoint.....you will incur the same problem,,,,,as a finish i use brushed joints and use veg oil as a weathershield

[@horserider9578]

if wet enters through the stone why does it not exit through the stone.

[@TheNixbrix]

cos its held in cem ribbon pointing

[@cob1965]

Hi Peter is there any circumstances you would use a stone sealer? We are repointing an old sandstone terrace in Lancaster with lime mortar and some of the stone at the base of the wall is spalling, do we need a stabilizer? We are taking the old cement mortar off.

[@WarmDryHome]

No... I'd take the spalled face off - it will have gypsum in it from acid attack - clean back to clean stone and repoint. If really bad, take out and turn the stones. A lot of that sort of damage is from acid fumes off traffic - nitric acid from diesel fumes. Use hotlime mortar not nhl if you can - nhl is too hard for that sort of stone.

[@cob1965]

Thanks for the advice peter. We are cob builders and If you ever need any help with repairs for cob, mud and stud or clay dabbins building let me know. Will post a picture of the work after we have finished. Great videos by the way.

[@WarmDryHome]

Cool - thanks.. bung me some info to [e-mail] and I'll do something on the site - we need references to people like you, and don't often come across them....

[@ChronoVersatur]

Classic looking example you have there Peter.I wouldn't mind if the cement pointing ever actually looked good but it looks god awful and simply wrong. We have many stone walls ruined near me. Cement pointing is caked on in various spots. There's even a once beautiful railway bridge caked in cement with this inch wide strapping that's lifting off. I feel like sending Peter pictures sometimes lol. Lastly I was visiting a National Trust Mansion/Park last year and come across your bog standard sand cement mix being used as filler on the mansion's huge stone blocks and wasn't even feathered in. Absolute eyesore and the last place I thought I'd see it. Hope it was temporary but the work that'd been done on the once amazing towering metal window frames makes me think not. They had wavy lines of gloss all over the glass. I kind of shudder when I think what the original builders and crafts people would say if they were brought back alive.

[@WarmDryHome]

+ChronoVersatur Be interested to know which one - might flip a comment to one or two key folks!