Tanking an Exterior wall

Discussion in 'Builders' Talk' started by limestone, Dec 4, 2006.

  1. limestone

    limestone Member

    Has anyone got any ideas on the best vapour barrier to use on the inside of a permanently damp exterior wall?

    The wall is stone built in 1825, solid, rubble filled, West facing and regularly subject to driving rain in the middle of the Pennines, so I don't think I can do anything to dry it out.

    It has been tanked with a number of cement render type finishes over the years, but because the building is built straight onto clay and is partial to a bit movement from time to time these finishes tend to crack.

    My idea is to use a membrane on the inside, under a dry lining system such as Gyproc with foil backed insulation as a backup and foil backed plasterboard on top of that.

    Does anyone see any potential problems with this and has anyone got any ideas for the best membrane to use?

    Thanks in advance
  2. limestone

    limestone Member

    Now does anyone have an answer to this?
  3. multi trade

    multi trade New Member

    Problem is maybe the floor ? I think the walls would be O.K Could the wall be re-pointed & silicon sprayed to help reduce the effects of the driving rain, silicon works well if the stone is sound (supposed to last several years)
  4. trustmark

    trustmark New Member

    think about this---
    Damp grts into wall damp showes internaly --if you tank internaly wall is still damp if there is enough damp / water it will push your membran away

    always go for external tanking if it works walls are dry if ti dosn't you havent done it properly

    if external tank isnt feasabel then the internal tank will require suport to prevent failure due to water preasure normaly by byilding anadditional inner leaf

    If that isnt posibel then I have yet to have any problrms with a quality SBR applied tank followed by SBR render even under conditions with active water preaasure

    dont confuse rendering with a waterproofing additive to with quality tanking system
  5. trustmark

    trustmark New Member

    haveing re-read your post--- you will have to excuse me ." I,m drunk" don't worry my dad used to say "A drunk man dosn't tell lies"
    anyway-- lots of waterproof render on your wall already so problem could be condensation which the wall can't absorb-- solution insulate
    Your idea and proposal are spot on maybe add a humidistate controled extractorif appropriate for the room.

    Just confirm weather moisture is internal trying to get out see this post or moisture trying to get in (see last post)
    apologies to all O-:
  6. Slimes

    Slimes New Member

    I've used foam backed plasterboard, dot and dabbed, to good effect in a similar situation.

    Cheers, Simes.
  7. limestone

    limestone Member

    Trustmark, you seem to know what you're talking about (drunk or sober), could I just ask what is SBR?

    To give more details to the problem, the building is a grade 2 listed chapel in the Pennines (so no external tanking allowed). The problem being caused by a mixture of lots and lots of driving rain on to the wall, and the same rain running off the roof and being blown onto/into the wall before it can get to the gutter (we're talking really extreme weather here).

    I have a couple of ideas to fix the guttering, but meanwhile the wall is soaking wet. This has obviously been a problem for about a 100 years as it has had all sorts of treatments and coatings over it's history including a type of render that looked as though it was mixed with bitumen.

    The wall should be getting progressively drier once the guttering is fixed as it has now been repointed but since it's about 2 foot thick and seems to be filled with soil rather than rubble this will be a really slow job.

    The wall is to be drylined with 50mm of insulation below the plasterboard to make the place habitable and the idea was to put a membrane on the wall first, cover this with 50mm foiled Kingspan, and finish off with foil backed plasterboard. Do you think that would do the trick or would a render coat be better than a membrane?
  8. yorkshireboy

    yorkshireboy New Member

    I have used this method on very wet walls before.
    Paint inside surface with a couple of coats of ruberoid dampproof.
    Fix treated laths to the wall.
    Insulate over all with 1" kingspan and cover with plasterboard.
    This method isolates the new wall from the old and has worked for me in similar situations as yours
  9. limestone

    limestone Member

    Thanks Yorkshireboy, That's the lines I was thinking about, but it's reassuring to hear from someone who has done it rather than me just jumping in and hoping for the best.

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