I have a bay window to repair with sash windows
and unusually no stone sub sill (see link below) instead their is a
wood sill,
which has rotted and been covered over with plywood.
I dont know if there was a sub sill originally.
My prefered method to repair would be to cast a new sill all round in
concrete, but my concerns are if I use a DPM between existing wall,
sash frame and new sill. It might not hold in place with the weight
of
the concrete (as their might be no grip).
If I dont have a DPM between sash and sill water might soak into the
frame and cause further rot / leaks.
Any suggestions would be appreciated from persons who know what they
are talking about and stick to the point.
Thanks
Martin

On 20 Aug, 21:07, Housemartin wrote:
I have a bay window to repair with sash windows
and unusually no stone sub sill (see link below) instead their is a
wood sill,
which has rotted and been covered over with plywood.
I dont know if there was a sub sill originally.
My prefered method to repair would be to cast a new sill all round in
concrete, but my concerns are if I use a DPM between existing wall,
sash frame and new sill. It might not hold in place with the weight
of
the concrete (as their might be no grip).
If I dont have a DPM between sash and sill water might soak into the
frame and cause further rot / leaks.
Any suggestions would be appreciated from persons who know what they
are talking about and stick to the point.
Thanks
Martin


Dear H Martin
If this were mine I would go back in wood as is using double vac Scots
pine and all the items previously specified on this group for double
hung sash windows

If, however, you want a subsill then unhesitatingly go and get a
thinish preformed one (pre cast) with appropriate stooling and drip
grooves and angle grind it to fit the bays
Make sure it is put in low enough ( you may have to take away a course
of bricks outside to fit a decent timber sill on top
Chris G