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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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  1.  
    Our 4-bed farmhouse was built in 1860/1900 using lime mortar and has been painted several times over the years since the 80's. The previous owners repainted about eight years ago using, I believe, Sandtex masonry paint judging by a can left in the garage when we moved in.

    I need to repoint and repaint the whole house as we had cavity walltie failure last year (1900 cavity with iron fishtail ties) and the brick stitching repair has left the 1900 part looking like a peppar pot. It also became apparent that a previous owner repointed sections using cement mortar and also what looks like polyfiller!

    Whilst looking into lime repointing I've leant that these masonry paints are latex based and tend not to let the house breathe causing damp problems which we are seeing. I'd like to remove all of this paint, repoint and then repaint with a breathable product. Can anybody suggest a decent method of removing masonry paint other than manual scraping which will take months? I've looked at chemical strippers, heat guns, sandblast, dustless etc. but I want to hear of proven successful methods that others have used.

    Thanks
    •  
      CommentAuthorfostertom
    • CommentTimeJan 1st 2017
     
    Me too - awaiting answers with interest. My guess is that the impervious Sandtex will have penetrated into the pores of the substrate, so nothing less that dissolving it out with chemicals (yuk) or hand-tooling off 2 or 3mm deep will do. Certainly, it's still the only way to remove paint down to clean ashlar stonework.The friction of mechanical methods might well melt it in deeper.
  2.  
    A look at the Sandtex web site shows on its first line - quote -
    "With microseal technology, our masonry paint ensures that surfaces are dirt resistant, breathable and waterproof"

    So if it is Sandtex it should be breathable.

    Before you try to remove what you have - find out what you have ! (e.g. contact the previous owner and ask them).

    I would be surprised if a sealed outer skin on a cavity wall would cause damp on the inner skin. What are the damp problems you are seeing. it could be that during the wall tie repair debris fell down the cavity causing a bridge and thus causing the damp - just a thought, but without details that is just speculation. Also were the damp issues evident before the wall tie work.
    •  
      CommentAuthorfostertom
    • CommentTimeJan 1st 2017 edited
     
    Is this a new formulation of Sandtex, moving with the times? AFAIK it's always been classed as impervious.
  3.  
    Posted By: fostertomIs this a new formulation of Sandtex, moving with the times? AFAIK it's always been classed as imprevious.

    I don't know - it is just what their web site advert says. However even if it is impervious I would be surprised if a sealed outer skin on a cavity wall would cause damp on the inner skin.
    • CommentAuthortony
    • CommentTimeJan 2nd 2017
     
    I would try lime washing a small section, I reckon that the paint won't like it and will curl up and come off. Sand blasting or pressure washing won't work. Elbow grease could and a needle gun in the right hands could make life easier.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 2nd 2017 edited
     
    Is it stone or brick.
    If stone, which is basically impervious, could you just scrape out the pointing (which you are doing anyway) and then repaint?
    • CommentAuthordelprado
    • CommentTimeJan 2nd 2017
     
    I highly recommend Peelaway. It's expensive but works really well. The key is to buy the cheaper one Peelaway 1 rather than 7 as its highly caustic only rather than relying on some nasty chemical
    • CommentAuthorbillt
    • CommentTimeJan 2nd 2017
     
    Posted By: delpradoThe key is to buy the cheaper one Peelaway 1 rather than 7 as its highly caustic only rather than relying on some nasty chemical


    ???????

    Sodium hydroxide and calcium hydroxide (Peelaway 1) ARE nasty chemicals. By comparison water and benzyl alcohol and kaolin are fairly benign.
    • CommentAuthortony
    • CommentTimeJan 2nd 2017
     
    Sounds like lime to me
    • CommentAuthordelprado
    • CommentTimeJan 2nd 2017
     
    Exactly, its not like the stuff that causes harm to aquatic life etc.

    Agreed the parts of peelaway 7 arent bad either but they are much less effective.

    Whereas most paint strippers contains horrendous carcgingenic stuff
  4.  
    Posted By: Peter_in_HungaryA look at the Sandtex web site shows on its first line - quote -
    "With microseal technology, our masonry paint ensures that surfaces are dirt resistant, breathable and waterproof"

    So if it is Sandtex it should be breathable.

    Before you try to remove what you have - find out what you have ! (e.g. contact the previous owner and ask them).

    I would be surprised if a sealed outer skin on a cavity wall would cause damp on the inner skin. What are the damp problems you are seeing. it could be that during the wall tie repair debris fell down the cavity causing a bridge and thus causing the damp - just a thought, but without details that is just speculation. Also were the damp issues evident before the wall tie work.


    I'm assuming it's Sandtex as a can of it of the same colour was found in the garage when we moved here in 2009 but was thrown out yonks ago. However, I cannot tell what layers are below it and the previous owner is gone. The paint is peeling and bubbling in a lot of places. The damp that we have seen is on an internal outside wall i.e. the original outer skin where a single storey extension has been built. Quite a few of the bricks here clearly show damp.

    Knowing that extensive yet isolated repointing has taken place previously using cement, and at times what looks like polyfiller, I'm prepared to repoint the whole lot in original lime mortar. I'll need to repaint anyhow but I just don't want to go through this whole process only to find this paint, or some other layer, is cauing problems.

    The following video sums up what we are seeing with the paint. When peeling the paint off the mortar and brick is damp, mouldy, wood lousey and smelling like the inside of a ping pong ball.

    https://www.youtube.com/watch?v=GLu5WWWIxf8
  5.  
    I'd rather have the house without paint but I fear it hides nasty brick work and the new ties will show with their mortar spots.
  6.  
    Im faced with a sort of similar situation except its a 1960s house with painted render... Ive experimented and washing the walls with a water jet washer and so far its taking off the paint without damaging the render
  7.  
    MonsterMonster I don't doubt that you have bad paint of some sort on the outer skin of the wall but I don't see how any damp would transfer to the inner skin unless the cavity is bridged. Perhaps remove a brick on the outer skin in an area where damp is shown on the inner skin to see how the damp is transferred to the inside.
    •  
      CommentAuthordjh
    • CommentTimeJan 3rd 2017
     
    Presumably there's no DPC in MM/Stuart's original house so rising damp is a possibility. What's the water level like outside the house? Lowering that might be an idea. Or looking for leaks on the first floor? What's the humidity like inside the house? Presumably you've eliminated condensation as a cause.

    But it seems to me that the easiest course is to try removing the paint using one or other of the methods suggested and then seeing what the situation is.
  8.  
    <blockquote><cite>Posted By: Peter_in_Hungary</cite>MonsterMonster I don't doubt that you have bad paint of some sort on the outer skin of the wall but I don't see how any damp would transfer to the inner skin unless the cavity is bridged. Perhaps remove a brick on the outer skin in an area where damp is shown on the inner skin to see how the damp is transferred to the inside.</blockquote>

    The majority of the damp is showing on the outside skin brickwork that is internal within the extension. The other damp is external where the paint is peeling. We have one room where damp is in a corner of a chimney breast (chimney previously taken down under roof line). The chimney breast is opened and is internal so in effect the rear of the fireplace is the external skin making its side a bridge across the cavity. This damp I believe it's from water ingress from the outside skin.

    Apparently the house has had cavity wall insulation as listed on the council building regs website but when opening up the wall when replacing Windows/doors and bricks taken out for tie inspection nothing has been seen. I'm rather hoping that cavity insulation was charged for but not actually done!

    There probably is something bridging the cavity. One interesting point is that the top 6 feet or so of the gable ends are solid brick. The house was built from the ground as cavity and the pointy bit of the gable is fished as solid brick work. Bear mind this was 1900 and cavity walls were just coming into being.

    All this aside my primary aim is to get the exterior paint off before repointing and painting. I think it's going to be a case of testing various methods on small patches and see what works best. Manually scrape where possible as a starter.
    •  
      CommentAuthorfostertom
    • CommentTimeJan 4th 2017
     
    Posted By: tonyI would try lime washing a small section, I reckon that the paint won't like it and will curl up and come off
    The building I'm thinking of has (allgedly) limewash over Sandtex and both remain pretty sound - but the wall shows every sign of being unable to re-dry, which has to be due to the Sandtex.
    •  
      CommentAuthorfostertom
    • CommentTimeJan 4th 2017
     
    The trouble with powered mechanical methods like sand or water blasting, needle gun etc is that you're working on a hard bit and come to soft bit and before you know it you've dug a hole in the masonry.
    •  
      CommentAuthorfostertom
    • CommentTimeJan 4th 2017
     
    MonsterMonster, does your house have 10mm 'bricklaying' joints, or fine 3mm joints like in early part of the video you posted?

    If the latter (and even if the former) then you have potentially very fine brickwork. As you're already talking of cutting out all joints and lime-repointing, it might be worth spending the money on a detailed restoration varying area-by-area, including in some places hand-tooling the paint like restoration stonemasons do, and finding a colour/texture matched way to re-point the wall-tie holes. Areas of surface-damage or spalling, once cleaned of coatings, can look acceptable, like honourable scars!
  9.  
    Posted By: fostertomMonsterMonster, does your house have 10mm 'bricklaying' joints, or fine 3mm joints like in early part of the video you posted?

    If the latter (and even if the former) then you have potentially very fine brickwork. As you're already talking of cutting out all joints and lime-repointing, it might be worth spending the money on a detailed restoration varying area-by-area, including in some places hand-tooling the paint like restoration stonemasons do, and finding a colour/texture matched way to re-point the wall-tie holes. Areas of surface-damage or spalling, once cleaned of coatings, can look acceptable, like honourable scars!


    From memory over 10mm. In some places where a previous owner has noticed the horizontal cracking due to the wall tie failure the mortar is at leat 15mm! I honestly would not say it's fine brickwork but very standard looking in the main. I've manually removed some paint and the bricks vary from yellow to red. Admittedly there are places where some doors and windows have been bricked up using more modern bricks. In these case I suspect they have been laid with cement mortar (and slapped on at that).

    Where the paint has scraped off from old brick there appears to be a powdery white layer.
  10.  
    I've just rediscovered my account on this forum and I'd thought I'd give an update to my masonry paint problem.

    I managed to get the paint off using a high pressure steam machine by these chaps https://tensid.com/

    This was used in conjunction with a paint softener called Home Strip. The system is very similar to the Doff system. It took me a week to strip one side of a five bed farmhouse and was incredibly effective. At the beginning my heart sank when it too me half a day to strip a several bricks. But using the paint stripper to soften the paint progress was rapid.
    •  
      CommentAuthordjh
    • CommentTime5 days ago
     
    Thanks for the update. Has taking the paint off solved the issue?
  11.  
    <blockquote><cite>Posted By: djh</cite>Thanks for the update. Has taking the paint off solved the issue?</blockquote>

    The bottom line is that the house feels warmer and drier after stripping and repointing.

    The paint was removed entirely in Sept 2020 and the whole house was extensively repointed with lime mortar. Prior to this we had some wall vents installed which revealed bridging of the cavity with masonry dust and lumps of mortar. I suspect some of this was possibly as a result of the installation of the new wall tie pins and using SDS drills but I couldn't prove it. The house was shaken for several days! A lot of this material was located at the foot of the wall and was manually removed by hook or crook. Anything that was caught on the new or old ties is still there probably.

    The original paint hid lots of cracks where the mortar lines had separated from the brick courses due to the wall tie failure. There was also a lot of old repointing using cement but has now been removed.

    The house was repainted using a silicate based paint that allows breathing to take place. So far so good.

    I located someone who did paint stripping and lime mortar work and I got them to strip the rest of the house as it took me one week to strip one side and then more to repoint. In all it took about four weeks to do the whole house. They used the Doff system which is very similar to the Tensid one I hired.
    • CommentAuthorvord
    • CommentTime5 days ago edited
     
    I stripped masonry paint off my brickwork. Used the DOFF system and got someone in as it's a horrible job. - paint stripper and a hot water pressure washer. On bricks it doesn't cause much damage but on stone you need an operator who is prepared to be careful.

    You'll find after many years soaking wet the lime mortar will have gone. It doesn't like being soaking wet.

    {quote}The bottom line is that the house feels warmer and drier after stripping and repointing.[/quote]

    It will do. When you get condensation (aka rising damp) it means your wall is sodden wet. Once that is sorted letting the wall dry to the outside you don't get the condensation any more. Probably a few degrees increase in temperature on the inside of the wall equivalent to a fair bit of insulation but more problem free.
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