Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)


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.

Buy individually or both books together. Delivery is free!

powered by Surfing Waves

Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.

    Any ideas on the greenest solution to tanking a new build basement? Many thanks in advance, Mike
    • CommentAuthorsquowse
    • CommentTimeApr 3rd 2010
    a concrete basement ? waterproof concrete i would have thought, the additives are relatively innocuous chemicals - needs a lot of care and supervision to get the joints right though, compared to the standard that most builders will work to these days.
    • CommentAuthortony
    • CommentTimeApr 5th 2010
    I didnt tank mine :smile: and it isnt damp yet
    I thought concrete was waterproof already. I had dug a hole in my basement floor (for various reasons) and the ground was wet - when I poured concrete to fill the hole, everything has been fine since - the concrete is completely dry. All that said, on the new house (where 5 feet of the basement wall is below ground level and on a hill where water flows down) - the outside of the concrete was sprayed with tar (probably not so green though). French drains were installed around the footings and everything has been fine and dry since construction.

    Paul in Montreal.
    • CommentAuthorowlman
    • CommentTimeApr 6th 2010 edited
    Do it on the outside before you backfill. I watched a German "kellerbau" company do one some years ago. The memory is a bit hazy but I seem to think the outside was first spray primed with tar/bitumen, then a layer of bitumenised metal or plastic foil was applied all round, I haven't seen it in the UK but it was in 1 mtr wide rolls, a bit like the small rolls of flashing, only bigger. Next a thick layer of insulation, sort of a tar impregnated polystyrene, and then backfilled, with a drain inserted around the bottom.

    • CommentAuthorowlman
    • CommentTimeApr 6th 2010
    Posted By: Paul in Montreal, I thought concrete was waterproof already.

    But Paul, I understand not vapourproof. It's the water vapour that moves freely through concrete,
    Have you already built the basement?

    Paul: ordinary concrete is not waterproof. Permeability improves with density. (Waterproof concrete can be produced by special additives and manufacturing techniques - usually at local ready-mix plants under direction of specialist hired-in technicians)
    Seems I over estimated the performance of regular concrete! This interesting article http://www.epicuro.co.uk/uploads/waterproofconcrete.pdf shows how waterproof concrete can be produced and how it's cheaper than waterproofing regular concrete. I guess that concrete barge I saw in the River Humber years ago must have been made out of special concrete!

    Paul in Montreal.
    • CommentAuthorsquowse
    • CommentTimeApr 6th 2010
    good quality concrete is waterproof - most of the problem is at the joints. additives do help in reducing the permeability right down. also you get a guarantee from the manufacturer.
    the outside tanking system is grace bituthene (i dare say there are other brand names). again it's the joints that are the problem. personally i would do the concrete top quality through supervision, joint strips and additives.
    • CommentAuthordazza
    • CommentTimeApr 6th 2010
    i have actually seen one tanked with stainless steel. they where in the stainless steel buisness and had a large tank that had been removed from somewhere for scrap. suppose it made sence to use it.
    • CommentAuthorCassie
    • CommentTimeApr 7th 2010

    Do you want the greenest solution or the cheapest solution, and what soil type are you in?

    Not sure on the greenest but we have looked into all sorts of solutions and I will happily offload - bit boring though!
    Hi Cassie. I would love to get the benefit of your research. Anything you can share would be great. I would like to spec the greenest but there is always a budget to keep to....
    • CommentAuthorCassie
    • CommentTimeApr 8th 2010
    Mike, I have sent you some info via e-mail

    • CommentAuthorCrofty
    • CommentTimeMay 16th 2010
    Cassie, would you mind sharing your information with me also?

    I'm only building a semi-basement integral garage (1m below ground level) with a bedroom above, but have no idea how to make it waterproof. Thanks:bigsmile:
    • CommentAuthorCassie
    • CommentTimeMay 17th 2010

    We used Grace Bithuthene 8000 with a drainage sheet ( which also acts as a protection barrier )but we got quotes from others. We never did get the quotes through from Visqueen for the torch on stuff.

    The Grace product is like Blue Peter sticky-back plastic !

    You brush on the bithumen, then peel of the backing of the membrane and stick it onto the bithumen, add the drainage sheet ( which is like mini plastic egg cartons) and backfill.

    Sounds easy but the sticky membrane is very very sticky and it you get it in the wrong place, or catch something against it then is sticks instantly and you cannot peel it off and have another go.

    I've got lots of info sheets etc so if you whisper your e-mail address I will send you some over.

    Here's a photo so you can see what I mean
    • CommentAuthortony
    • CommentTimeMay 17th 2010
    What happens to the moisture in the basement? -- concrete is vapour permeable and to me the vapour-proof layer should be on the inside?

    presumably you have no problems?
    • CommentAuthorCassie
    • CommentTimeMay 17th 2010

    On the other side of the concrete wall you can see, there is a cavity ( insulated ) and then internal skin. Then its my living space with MVHR and normal air movement caused by general living, doors and windows opening etc, passive solar and then woodburners, so all in all should dry out quickly and remain that way.

    I will let you know if there are problems after being in there for a winter!

    The tanking is to stop a potentialy large amout of water getting through that concrete wall, we are in heavy clay here, and there is no way on this earth I would have got mortgage funding without it.
    Posted By: tonyWhat happens to the moisture in the basement? -- concrete is vapour permeable and to me the vapour-proof layer should be on the inside?
    It stays in the basement ... or, really, it just enters the air in the conditioned living space.

    Our (new) basement is treated in the same way - all the waterproofing is on the outside (again, due to high water pressure due to underground streams coming down a hill). Nothing on the inside, and nothing under the floor either for that matter. Everything is bone dry inside.

    Paul in Montreal.
    • CommentTimeMay 17th 2010
    Property care association - structural waterproofing

    (turn speakers down before clicking on 'online guide')
    • CommentTimeMay 18th 2010
    The waterproofing ought to be on the 'wet' side of something strong/rigid - so that if there's hydrostatic pressure it will press the membrane against its backing - if not so, then the pressure may want to blow the membrane off, only resisted by its stickiness. Remembering that 1m height of saturated ground against a vertical membrane will be exerting an inward hydrostatic pressure of 1 tonne per m2 at its top, in addition to the pressure due to the mass of the solid material. In theory, if the ground can be guaranteed unsaturated, e.g. by french drain, then it should all get much easier - but all the regulatory influences want to discount that and assume the worst.
    This is the method we went for. http://www.bbacerts.co.uk/PDF/2278i2_web.pdf See page 5 detail for external tanking
    in 99.9% of cases a good quality precast basement does not need tanking and will be supplied with a full warranty for a number of years.
    • CommentAuthorRich T
    • CommentTimeJun 8th 2010 edited
    We've used visqueen torch on for the soil side of our basement, although the technique was slightly different to what Cassie had to do, our experience was similar. It was a horrible job. First you prime the wall, then peel off the backing paper, stick the visqueen on and then blow torch it.
    The visqueen is very sticky and once you've peeled off the paper backing and let it touch something, there's no going back. It is a two coat application which provides a homogenous coating.
    Once we'd applied the visqueen it was then covered with a protection board to stop damage from things like stones etc.

    On the inside of our wall we have used vandex BB75, which is great to put on, even for a couple of DIYers. It's permeable, and we will go on to vandex our foundation slab.
    Our building inspector has been very keen for us to use this method of tanking.

    Edit: We've also put in a top perforated drainage pipe along the bottom of the basement wall, and also one at approximately 400mm deep.
    You use concrete first so do it well.
    Concrete, waterproof concrete, is the only waterproofing measure that cannot be destroyed by others later.
    The membrane in the photo above doesn't stand a chance against a digger backfilling or the wacker plate compacting the soil. There won't be any left.
    • CommentAuthortony
    • CommentTimeSep 13th 2014
    or against moisture in the air inside being drawn through the concrete in vapour form and condensing on the back of it when it is very cold outside. Even waterproof concrete is not impermeable to water vapour.
Add your comments

    Username Password
  • Format comments as
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   

© Green Building Press