casting a concrete window sill.

[Housemartin]

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 [IMG]

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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