On 23/05/2013 11:49, Peter Percival wrote:
I have inherited a shed made of cast (or moulded, whatever the word is)
concrete for the lower walls on which the rest is built of wood. (It
has a made-up as it was constructed look about it.) The wood is rotten
and I need to replace it. How can I attach the new wood to the
concrete? I could use screws--those things that expand against the hole
they are in when an internal screw is tightened--but that will leave a
crack 'twixt concrete and wood where the rain might get in. So I need
(I think) an adhesive cum sealant. Any suggestions?

Not quite enough description. Do you mean the base is made of those
pre-cast panels which sometimes whole garages are made of? These are
thicker at the edges where there is reinforcing rod, and thinner in the
middle.

Or are you saying that the walls were cast in place with formwork which
was subsequently removed. How thick are they?

And how is the wood fixed? Does it overhang the concrete, or is it
mounted on it.

You *don*t generally want an expanding thingy in the concrete, that is
asking for cracks unless the thickness is substantial. But if you rest
something like a wall plate on top of the concrete, then hang panelling
/ T&G / Feather Edge outside, you could prevent it blowing off in the
wind by having the panel overhanging the concrete, and bolted to it with
normal coach bolts going through holes in the panel below the rebar. For
adhesive / sealant, any sort of external mastic / frame sealant should
do. But I would want some sort of mechanical fixing as well against wind
forces.