Rising damp in a sandstone house

Discussion in 'Builders' Talk' started by Rachael Large, Mar 29, 2017.

  1. Rachael Large

    Rachael Large New Member

    I've been advised that injection damp proofing does not work on sandstone houses, can accept that. I am planning to use some tanking materials, stripping off all the old plaster first.
    Is this the best way to go or are there any other alternatives? Have looked at vandex bb75 but am not sure that is the right thing to use in an old house, it's a small terrace.
    I will get some surveys done however would like to do it myself if possible and information is always a positive.
     
  2. Wayners

    Wayners Screwfix Select

    You need to get advice from a pro. Find local companies. I see these guys for time to time and they know there stiff. You may need a certificate at some point to. I have seen the new vents they use and injection. Need the right solution for the property though. Not really a thing you can do yourself although I helped a chap with injection kit he hired many years ago. That's easy enough
     
  3. Rachael Large

    Rachael Large New Member

    Thanks, going to get a few companies in to have a look. I've been told that I can't use injection because it's sandstone. I've used that before in a garage and it worked really well.
     
  4. KIAB

    KIAB Super Member

    Stone needs to breathe,sealing it is not a good idea.

    Is it all external ground floor walls, or just one, have you ruled out other causes like leaking gutters, drains, water pipes, soil banked up against wall, water running towards a wall.

    Are ground floors solid or suspended, if suspended are the air vents cleared, if blocked can cause damp/mould problems to timbers & walls.
     
  5. Rachael Large

    Rachael Large New Member

    It's not just the external walls, it's internal ones too, and the back yard is at the same level as is the front of the house so its not been built up. I have thought that finding someone who can do the old lime render and so on May we'll be the best because it's better off breathing ..
    There are two different floors, front room is suspended and back room is concrete .. Not sure what the reason is, but ...
    Will check the vents though, had forgotten about that, thanks.
     
  6. KIAB

    KIAB Super Member

    You need a good through airflow under a suspended floor front to back,wonder if they put ducting in concrete to get this.
    Presume you got a crawl space,might paid to have a nosey down if possible.

    Good thing with lime render it allows the walls to breathe & moisture to escape.

    Have you always had damp or has it just started appearing.
     
  7. sospan

    sospan Screwfix Select

    You may find that the new the new concrete floor is restricting air flow under the timber floor. Typically you need at least two vents one front and one of the back.

    Other things like changing the internal floor covering vinyl, hard boarding a floor before carpeting or putting down a click flooring system will also affect airflow

    The other thing is to look for a slow leak in a pipe/condensation - when I bought my house, I had damp near the front door, it turned out to be a weeping joint two rooms away in the bathroom
     
    KIAB likes this.
  8. KIAB

    KIAB Super Member

    Your thinking the same, lack of airflow, or slow leak.
    Funny thing with water it never takes a direct A to B route, always has to go the long way around.
     
  9. sospan

    sospan Screwfix Select

    And of course sandstone being porous will absorb water like a sponge but also being porous will dry out quickly unless it is topped up by a water source
     
  10. KIAB

    KIAB Super Member

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  11. Mr Rusty

    Mr Rusty Screwfix Select

    Hmm. Working on a similar house. Front was suspended, back was solid floor, and all internal walls around solid floor room showed signs of "rising damp", except I'm pretty sure it wasn't. The concrete floor turned out to be flags on sand only. The old fella who lived there, lived in that one room mostly, solid fuel fire most of the time. Pretty sure the "damp" was actually condensation from vapour released through the floor into the warm air (even though it had 5 layers of lino and 2 layers of carpet on) and vapour from the fire condensing out on the coldest part of the wall. It started drying out straight after the house was unoccupied. We've since reconcreted all the ground floors with insulation and DPM. The house isn't yet lived in and currently has no heating, but all the walls, stripped of their plaster, now seem dry as a bone. If there was "rising damp", it sure ain't there now.
     
  12. Rachael Large

    Rachael Large New Member

    Will get the flooring up as soon as possible and have an investigate and see how it dries out. More investigation needed before any decisions then.
    Thanks for all the advice so far.
     
  13. Mr Rusty

    Mr Rusty Screwfix Select

    Bit more info on my project. When we lifted the flags the sand underneath definitely had some moisture in it - I say sand, but it was really 2" sand over cinders over bare earth. All dug out, and remade as a new concrete floor with insulation and 2x DPM. The front room was suspended. Immediately behind the front wall, the underfloor level was approx 400mm below outside ground, and was wet. The house does have bitumen DPM in both outer and inner skin (despite being 1902) and little sign of "rising" damp. However, there had obviously been a long-term problem with floor joists rotting in the front room because of underfloor moisture. Joists had dry rot, floorboards worm (which also like damp). All stripped, made up, and concreted.

    I expect you may well find the solid floor in the rear room is original and doesn't have a DPM. As others have said, suspended floors need good ventilation, but if the house has been surrounded with hard surface that in any way runs towards the house, it will be difficult to keep the underfloor bone dry.

    IMHO the challenge in old houses is that they were built in the days before central heating (so were colder). Warm air can hold much more water vapour. Condensation is a much bigger risk in a warm house, if there are still any cold surfaces. Also, houses originally had breathable floors - flags over sand, floorboards, that allowed water vapour to disperse without too much condensation. Lime plaster walls that could breathe. There were also more open chimneys providing ventilation. Now we seal our houses up, make them nice and warm so the air can absorb lots of moisture, and we wonder why we have big problems with condensation. To keep a warm house dry, it needs to have internal insulation to avoid cold spots/surfaces and good membranes to keep the external damp outside, plus ventilation.

    Is there a cavity? if so I would think very carefully about CW insulation on an old house, because whereas modern walls with cement mortar are virtually waterproof, older walls with lime mortar are not - that cavity IMHO needs to be ventilated and that means air circulation - you may well find some of the airbricks are just in to the cavity only.

    There are lots of different opinions out there, but my own view, FWIW, is to use insulated plasterboard inside on external walls which incorporates a DP layer. This removes cold spots and hopefully keeps any damp in the walls, in the walls, and hopefully cavity ventilation removes any damp within and keeps the inner skin dry. Floors with DPM should prevent water vapour coming up through the floors. With the rooms sealed to the same standard/extent as a modern house, the only water vapour is then created by people living in it - cooking, showers etc.

    Not a great fan of the "use lime plaster in an old house" argument, unless you go the whole hog and also use old fashioned paints/distempers. I can't see there is much point having breathable plaster and then covering it with vynil silk emulsion!

    I am no expert - so make up your own mind - this is just my opinion.
     

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