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Stuart Noble Stuart Noble is offline
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Default waterproofing timber formwork for complicated concrete shape

Andy Dingley wrote:
On 18 Jul, 19:02, tonyjeffs wrote:

Any ideas on a better way to water-protect the formwork?


I tend to use shellac, because it is easy to repair the worn surface
(shellac bonds well to old shellac). Varnish is strong but not so
sticky, so you can find it flaking off.

I also prefer wax (liquid emulsion of wax in wate, as sold to wood
turners) rather than oil. I've had one job where things came out with
an oily rainbow sheen and it didn't shift for years afterwards!

Secondly, I think there is such a thing as a washer with teeth around
the edges, which I could nail over a screw hole so as to ensure that
the screw can only go in the correct place.


T nuts. They're intended to take an M6 screw or similar, but they also
work fine as a hammer-in hole reinforcer for dowel pins - they're
cheap enough too. You might even find that a machine screw is a better
choice than a woodscrew anyway. If you're using MDF, then use a screw-
in threaded insert rather than a T nut.


Vaseline, or anything from the mineral oil family e.g. paraffin wax.
Good waterproofer and a good release agent