Log Cabin DPC Help

Discussion in 'Carpenters' Talk' started by Knobby, Jan 29, 2017.

  1. Knobby

    Knobby New Member


    I build a wood cabin about 2-3 months ago.. I need some help with DPC..

    Its constructed with a concrete base, then a DPC layer, treated bearers and then the log cabin built on top of this.

    I have damp rising up the walls inside in the corners and now its started going mouldy.

    Any suggests on how to fix this?


  2. GordonK

    GordonK Member

    Sure it's not water coming in the roof and running down to the corners ?
  3. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Yep most likely the water at the corners running down, settling at the bottom - last thing to dry out.

    Mr. HandyAndy - Really
  4. wiggy

    wiggy Screwfix Select

    Does your exterior cladding go down past the slab?
    Did you breather membrane the walls?
    How is the exterior corner detail finished?
  5. Knobby

    Knobby New Member

    Thanks for the replies..

    The roof is pretty well waterproofed.. felt shingles, OSB, celotex, vapour layer, roof boards.. Both gable end weather boards and siliconed well.

    Unless its water hitting the side of the building.. Its only the corners showing damp.

    Its slab, bearers, cabin, no cladding goes past the slab.

    No beather membrane, its single wall construction.

    Here is an example picture.

  6. wiggy

    wiggy Screwfix Select

    Water could be splashing up?
    Treat it with some sort of clear waterproofer.
    I can't see where there could be a problem other than ingress at the corners
  7. sospan

    sospan Screwfix Select

    Condensation ?
    wiggy likes this.
  8. wiggy

    wiggy Screwfix Select

    How long has it been up?
    The timber could be drying out, with no ventilation in there would cause condensation
  9. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    If the corners are like that in the picture, that's a bad design and definite rain-trap.

    Mr. HandyAndy - Really
  10. Knobby

    Knobby New Member

    Most log cabins have this construction.. Its painted with Sadolin Superdec so should waterproof on the surface.

    The damp comes and goes.. During dry spells it goes. Its certainly linked to rain/damp spells.

    It's been up for 2-3 months. There is zero condensation on the underside of the roof, glass in the doors and windows also have zero condensation. I've insulated the floor and roof to stop condensation. Under the floor boards under the vapor membrane the moisture is high.

    I am yet to treat and paint the inside, wanted to fix this problem first as I thought there was a risk I was just trapping the moisture in the logs..
  11. wiggy

    wiggy Screwfix Select

    How far up the wall or down the wall is the mould
  12. wiggy

    wiggy Screwfix Select

    Just 're read your op. Up the walls.
    It has to be rising than.
    You say you doc down. Is it under every joist. Could be worth creating some airflow under there. Lift it an stick it on bearers. Should be easy Enough to do.
  13. Knobby

    Knobby New Member

    A few pictures of the actual build to show you the construction..

  14. Knobby

    Knobby New Member

    See above picture.. It under every bearer thats in contact with the floor.. I know some in the picture don't have DPC under them but it was added later.

    How do you suggest lifting? The complete structure?
  15. wiggy

    wiggy Screwfix Select

    Get a spade under one corner and Jimmy it up. Stick a brick under it or something.Then go to next corner on the short side and do the same. Then slide a bearer under there. Do the same on the other end and then the middle. Run your bearers the oposite to your joists.
  16. wiggy

    wiggy Screwfix Select

    Just seen those other pictures. Water is getting under there for sure. Almost guarantee creating airflow under there will solve it. If you ever do similar stop the slab under the building. Yours sticks out a couple inches by the looks of it
  17. GordonK

    GordonK Member

    You need an air flow under the floor. It doesn't look like you have any air gap to let things dry out after rain etc ... think of your hous and air bricks etc.. I'd put money on it needing to be raised up. My last cabin I had a gap of about 4" between the floor bearers and the ground ..no dampness at all and it was up for about 10 years before I moved house..

    Hard to see but is that timber floor frame just inside the walls... the walls look like they sit right on the concrete... if so that's a no no..
  18. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Yes, water is in contact with concrete, concrete is in contact with cabin.

    Mr. HandyAndy - Really
  19. Knobby

    Knobby New Member

    So under my floor between the bearers and supports I have small bits of treated batten, celotex, then a vapour membrane and then the floor boards on top.

    Between the concrete and bearers is a DPC layer, the bearers and log cabin are in direct contact. Others have said a DPC layer would help.

    The manufacture suggests the concrete base be the same size as the bearers and the log cabin protrudes slightly so water drips off and misses the bearers and base.

    Where is this air flow coming from?
  20. wiggy

    wiggy Screwfix Select

    Your concrete looks like in protrudes past the frame. Water is getting under your building. You need to lift it up to create airfolw.

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