This isn't DIY, but you guys were helpful with my last question about my
basement and so I'm hoping you can help again. Sorry for the slightly long
post, but detail might be relevant.
Builders are currently tanking and converting my basement and have installed
a waterproof membrane, drain and well/pump in the main area of the basement.
However they've said that they've had to change plan on the stairwell which
leads to the basement, due to the restricted width leading down there (there
are brick walls on either side of the stairwell). Instead of hacking back
the plasterboard which is dot-and-dabbed to the walls either side, fitting
the membrane, battening and replasterboarding as originally planned, they're
applying a Visqueen liner directly against the existing plasterboard, over
which they're fitting ply and painting. This Visqueen layer will be taped to
another sheet of the stuff which will run down the stairs and which will be
covered by thicker marine ply.
Apparently, the walls either side aren't straight (or square with the
stairwell) and to fit the membrane would require the wall to be rebuilt,
which would cost extra. If I'm mistaken then I'm sorry, but that sounds like
total bollocks to me. Wherever else the wall hasn't been straight, they've
compensated with the battening, which they've fitted ON TOP of the membrane,
before affixing the plasterboard. I don't see what bearing the straightness
of the walls have (within reason) on whether the tanking system works or not
and, although the stairwell certainly isn't dead square with the walls
(carpet had to be fitted in two step sections) it certainly isn't
The stairwell footing is concrete slabs resting directly on the ground (soil
etc beneath the house) and, when the brick walls either side were first
plastered (dot+dab plasterboard skimmed over) and carpet laid over the
concrete steps, I very quickly saw signs of mould and damp coming in on the
plasterwork, near the base. At first this was treated by stripping off the
affected plasterboard, scraping the bricks and concrete steps clean of
mould, applying mould killer, leaving for a week and then applying a rubber
waterproofing solution, before replastering. The mould hasn't returned yet,
but I suspect it will if not fixed up properly, albeit it might take a
longer period of time. Certainly the paint-on rubber solution is already
full of holes and the current solution doesn't strike me as "proper".
My concern is that these tanking systems are built specifically to allow
trapped moisture to drain away at the bottom or evaporate through the top.
Visqueen sandwiched between ply and the plastered wall (fixed as described
above), taped to another sheet of Visqueen running down the stairs, in turn
boxed in with ply, doesn't sound convincing.
Am I being unfair? Is this an acceptable solution when required?
Thanks in advance.