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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthoroink
    • CommentTimeFeb 1st 2018
    Hi all,

    I've moved into an old stone cottage and am looking to get wood flooring in the living room. The floor is concrete, no idea when it was laid. The chap who will be installing the wood floor has tested the concrete and the moisture readings are high; upto 85%. He has suggesting using ARDEX DPM 1C to protect the floorboards.

    My concern is the 'breathability' issue. I'm a complete novice to old buildings but have been trying to educate myself, albeit slowly! Despite having cement pointing externally there doesn't seem to be any damp issues in the walls but my concern is that by stopping evaporation of moisture through the floor it could divert it to the walls, where it would then have trouble finding a way out. I did ring ARDEX and the chap on the phone reassured me that their product doesn't stop moisture passing through, it just controls the rate to a level low enough to protect the floor, while still allowing the moisture through and therefore not forcing the moisture into the walls. He really did sound knowledgeable but I thought it almost sounds too good to be true.

    I was just wondering if anybody had experience using a liquid dpm in an old house, or more particularly, if anybody has had any problems using one? Or if someone had any advice for me?

    Thanks in advance,

    • CommentAuthorIan1961
    • CommentTimeFeb 1st 2018

    I haven't used a liquid dpm in older properties but I've used it myself on a domestic extension and as an architect I've specified it for use dozens of times in fast-track commercial projects where there wasn't enough time in the programme for concrete floors to dry naturally. It works exactly as described by your contact at Ardex in that it isn't a complete barrier to moisture however it slows movement of moisture down to a level where it doesn't cause a problem. I've never had a subsequent problem with moisture transmission affecting sensitive floor finishes such as timber after applying a surface liquid dpm.
    What is the internal plaster on your walls?
    • CommentAuthoroink
    • CommentTimeFeb 2nd 2018
    Thanks Ian, much appreciated

    I'm not 100% sure of the internal plaster. It's difficult because the whole house is a bit of a hotch-potch depending on if it was touched during the 'update' in the 1970s. Upstairs I've redecorated a couple of rooms and the plaster does appear to be lime based but I'm unsure if downstairs, where I'm looking to put the wooden floor, is lime or gupsum.

    I've actually just been in to the livingroom and scraped a small hole in the painted plaster and the top layer of the plaster looks white. Elsewhere on this website someone said that's a good sign that it's lime plaster but as I said before, I'm not 100%. The previous owner mentioned to me that the room was painted in clay paint for it's breathability properties so I think that hints that at least he assumed it was lime plaster.
    • CommentAuthortony
    • CommentTimeFeb 2nd 2018
    This idea of breathable sounds good but what does it mean?

    Draughty, allows the passage of water vapour, allows oxygen through, allows smells to get out, ??

    Certainly a liquid applied damp membrane is not going to be breathable.
    • CommentTimeFeb 2nd 2018
    Posted By: tonyCertainly a liquid applied damp membrane is not going to be breathable.

    So you're saying Ardex are lying?
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