Rick wrote:

On Fri, 18 Mar 2005 16:57:10 -0000, "daveasbury"
wrote:


Could anyone help with a very annoying problem.


I recently decorated my dining room which has a five sided bay. I ripped out
the very old window sill and made good
the plater underneath that broke away with plaster board sat on top of
plasterboard bonding (the whaite doughy stuff).


I made the window sill out of cill board (mdf pre coated) and stuck it down
to the plasterboard with a polyurothene adhesive that is used to fix/glue
buses together with. It's basically a very adhesive silicon sealant and
certainly better than no nails.


All went well except every couple of weeks I get the paint cracking at the
joints. I've used decorators filler. But they re-appear.


I'm thinking expansion and was going to drill through the would and screw
the sill in place.


The paint is crown solo - it's very thick like emulsion, and i've given it
about 4 sand and coats now...





I think you will find the bricks expand at a different rate to the
wood, and thats where your problem comes. To keep the wood solid in
one piece, I guess you need to make the window cill into one piece,
with biscuit joints or similar, and then stick it to the bricks with
something a bit flexable.

As to cracks between plaster and wood, the only way I have ever gotton
close to fixing this is by using silicone to fill the gap, as silicone
remains flexable.

Docorators filler goes hard, so will crack if put between surfaces
that have some movement.

Acrylic does retain some flexibility - acrylic decorators caulk is teh
bvees knees, but in very thin cracks it struggles

It is not clear between what elements the cracks are appearing- please
elucidate.
Rick