We worked on the sill for our big window in the south wall of the east wing. Two reasons. Firstly it is the last complete opening still missing its sill. Secondly, we cannot finish insulating the east wing until it is done. It is around 3m high and wide and we had left it with the foundation blockwork built up to finished floor level, with tanking membrane laid up the back edge. We decided to leave it as is and to build the sill on top. This will lift the window proper above floor level, reducing the possibility of anyone accidentally running anything directly into the window frame or glazing. In fact, we do not have a sill that is 3m long, we will prepare two of our 1.6m lintels and join them in the middle.
The blockwork at the base is 100mm. This a bit skinny and we wanted to widen it nearer to 200mm. We dug out the ground immediately in front to foundation level and laid concrete above it, to level it up to 200mm below ground. We mortared a second course of blocks in front, to ground level, then faced above it with a thin layer of granite and finally a course of lime mortar above to create a 10-degree slope outwards. Once it had gone off enough, 48 hours or so, we lapped tanking membrane up and over the mortar.
We found two lintels that matched in height and width and processed them as we had our other sills. Propping the sills at a 10-degree angle, we sliced the fronts vertically off with the angle grinder and bush-hammered the faces. Then we cut the undersides at 90 degrees to the front and sliced drip grooves into them. Finally it was a case of slicing them to length, notching either side of the window opening so the ends of the sills slotted into them. We did a dry run installing them, to check the alignment and that they fitted. They lined up well, with a gap of a couple of mm between them. We fitted eight of our chunky steel angle brackets to the blockwork underneath, stuck strips of foam on the base to spread the weight of the sills and put them in place permanently. We used squirty foam underneath the sills then screwed the sills to the angle brackets. And that was it, though we will need to fill the gap between sills, possibly with epoxy resin mixed with stone dust.
East Byreleask Steading 