Hi,
I have a small window which has never had a sill as such - just a flattish plastered bottom to the opening. I now want to tidy it up a bit, so I've bo ught a length of ready-made MDF window-sill and trimmed it to fit.
With the sill in place, it becomes very apparent that the bottom of the ope ning is not level in either direction - it slopes down towards the inside o f the room, and also has a slight slope from right to left. I made a reason ably tight fit when trimming to length (more by luck than judgement, especi ally since the ends are not square either!) so it sits straight and level b y friction with the sides, but there's a gap underneath it of around 10-15m m (varies) across the front, sloping to nothing at one of the back corners and very little at the other.
I imagine there's a proper craftsman's way of fixing this with precision jo inery, but to be honest I can't really be arsed :-). Instead I have visions of spreading some sort of mortar or filler across the whole opening, then pressing the sill down onto it and tapping it down to level a bit like layi ng a big tile. Then smoothing off the front where it will squeeze out of th e gap, to leave a "finished" surface (or as finished as a 15mm strip undern eath a window-sill needs to be).
So, finally, to my question - what would be a suitable material for this, p referably obtainable in a chain shed tomorrow? If it also sticks the board in place then so much the better.
Cheers,
Pete