Damp penetrating through concrete floor

Discussion in 'Building' started by Amphibian, 31 Jul 2011.

  1. Amphibian

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    I have damp to the base of an internal partition wall. I believe the cause is manifold, but believe it is caused primarily by the fact the outside floor level is the the same as the concrete kitchen floor and that as the drain pipe discharges onto the external ground the water penetrates through the base of the wall into the concrete floor and then on to the internal wall.

    Now the obvious solution would be to lower the external ground until I find the damp course, if indeed the house has one, it's a Victorian house built on the base of a Georgian cottage so it may not.

    The problem is that the ground outside is a concrete path that runs down the rear of the terrace, it is a shared access path and runs in a single piece for the entire length of the terrace. I suspect it was laid on top of an older path and that's why it is too high, but if I was to just lower my piece I would be lower than my neighbours and without new drainage it might turn into a paddling pool putting more water against the wall.

    Installing a new drain might solve the problem, the SVP enters the ground through the concrete so a drain must lie below, close to the wall, I hope that's not the source of the damp, though under the new laws it would likely be the responsibility of the water company if it was. I know you're not meant to drain your roof in to the sewer, but there is nowhere to construct a soakaway as my garden is not contiguous with the property.

    If it was impossible to lower the path, what are my options? Is it possible to dig a trench and waterproof the wall on the outside then reinstate the path? What if I took up the concrete floor in the kitchen and tanked the wall before reinstating it with a DPM underneath? Though if I did that where would the water go instead?

    What if I took up the path, inserted a French drain at the far edge, sloped the path towards the French drain and filled above the trench with gravel. What is the closest to the house you can use a French Drain? The path is probably only 3-4' wide.

    Really unsure how to proceed with this.
     
  2. RedHerring2

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    OMG, slow down and take it easy, there's no rush!

    How do you know you have damp at the base? Partition wall? what does it partition?

    Wrong use of the word manifold really. A manifold is something else to do with plumbing.
    And your assumption might be correct. But more info' will be needed for a proper diagnosis.

    Are you serious? And what drainpipe?

    If what you've said so far is true, then, yes probably.

    Might be a good start. It's called "intrusive investigation". "Un-intrusive investigation" is taking measurements, researching history, etc.

    Probably. Do your neighbours have a problem?

    It might. Have you given this much thought?

    If you understand this much, it suggests that this might be a wind-up.

    Has this been the problem always, or just appeared? In which case we're talking repair, not alternatives.

    Don't know yet.

    Yes, but is that the best option. Don't know yet.

    One option. The best?

    Don't know yet.

    Where would the water go? BTW, a French drain is a trench filled with gravel.

    As close as you can get. Where would the water go?

    BTW, this post really should be in the "Building" forum. Ask the mods to move it for you.
     
  3. Amphibian

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    Okay, sorry. Thought I'd give as much information as possible rather than just say, I have damp and wait for others to tease the information from me.

    The damp has been thrown up on a survey (it's a house only just coming into my ownership) The partition wall lies in the middle of the house between the livingroom and kitchen and runs parallel to the front and back wall at a right angle to the party walls. I have spent little time in the property but saw little evidence of visible damp when there, it has been very wet recently so I don't think we're talking a big issue, just one I'd like to resolve.

    Manifold has uses in car mechanics too, but also has a perfectly valid definition meaning 'many and various'.

    The main drainpipe running from the roof to the ground and yes I am serious (it is an old cottage, probably built for estate workers probably on the cheap at the time)

    A lack of air bricks into the solum would further exacerbate the issue too.

    I am afraid i don't know, I don't have possession of the property yet.

    Not at all, I can use google but I am not a builder.

    It may always have been a problem, I don't know. The path was probably lower in teh past, the house heated with multiple open fires and plenty of drafts to dry the walls out etc...


    Oops sorry. I'll ask.
     
  4. RedHerring2

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    I'd wait until you're living in the house and then assess the situation.
    Has the house been left empty for a while? This could be a cause of condensation.

    Damp surveys nearly always find some damp, that's how they get their work.

    It seems highly unlikely that the exterior wall is not damp but an interior wall is. And you say there's little evidence of damp, so far.

    You can't install airbricks without lowering the exterior ground level, and anyway they're no good for solid floors.
     
  5. Amphibian

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    Sorry, the airbricks would be for the front wall of the property, the living room has a suspended floor, the kitchen at the rear is a solid floor. As the damp is to the rear wall and the wall dividing the two rooms internally I though airbricks might help vent the solum under the living room and improve the damp to the dividing wall. The ground at the front of the property is a good 3' lower than at the back, the property is built into a slope.

    The front wall is dry, as are the party walls, the damp is to the internal wall and rear wall and the solid floor in the kitchen.

    The property has not stood empty.

    the survey was not a damp survey and was not carried out by a tradesman.
     
  6. RedHerring2

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    I'd still wait until you've been living in the property for a little while. This will give you at least two advantages:
    You'll be better able to assess the severity and perhaps the cause.
    You'll be better able to assess your neighbour's situation.
    You'll be better able to assess the possible remedies.
     

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