Hello,
I'm repairing an old barn roof which I've been trying to keep as dry as possible with a succession of tarps for about 10 years. I've given up on tarps since Storm Darragh - fed up with them being shredded and horrified by bits of plastic being blown all over the place...
I've been strengthening the existing rafters, some of which are badly rotten. The existing rafters were cut to finish at the edge of the wall plate rather than extending beyond it with a birdsmouth. The roof ridge dips a bit at the centre, and between the A-frames and gables. The old rafters dipped with the purlins which have sagged between and either side of the A-frames, but obviously the new ones don't so they just run straight from wall plate to the ridge. I've screwed the old and new rafters together. The rafters are 3.385m at the shortest points, whereas those at the gables are 3.440m so there's a difference of 55mm to absorb.
The roof pitch is 40 degrees and faces south.
I'll fit the fascia board to the wall plate using spacers to give a 10-15mm air gap behind it.
With a 50mm tile overhang into the gutter, 20mm for the fascia board, 15mm air gap the maximum roof 'depth' (I'm not sure of the right term for that dimension? Can't be span, width or length..?!) would be 3440 + 85 = 3.525m
I'm re-using the old double romans, and will buy more. They're around 410mm long, with a few mm variance between different tiles.
If I've got this right, I calculate that a 90mm headlap means each tile will cover 320mm, so 11 rows will cover 3.520m
Q1: Is that right?
Q2: Is 90mm headlap enough for these tiles?
If I add an extra row of tiles, each tile will only need to cover 3.525/12= 293.75, say 295mm, which would give a 115mm headlap.
Q3: Would that be too much..? If not, is this better than 90mm? And is it necessary?
Q4: Is the batten gauge the same as the tile coverage, i.e. 320mm for the 90mm headlap / 11 rows, 294mm for 12 rows / 115mm headlap?
Q5: What's the best way to "absorb" the differences in rafter length / roof depth?
Many thanks, in anticipation, for responses..!
I'm repairing an old barn roof which I've been trying to keep as dry as possible with a succession of tarps for about 10 years. I've given up on tarps since Storm Darragh - fed up with them being shredded and horrified by bits of plastic being blown all over the place...
I've been strengthening the existing rafters, some of which are badly rotten. The existing rafters were cut to finish at the edge of the wall plate rather than extending beyond it with a birdsmouth. The roof ridge dips a bit at the centre, and between the A-frames and gables. The old rafters dipped with the purlins which have sagged between and either side of the A-frames, but obviously the new ones don't so they just run straight from wall plate to the ridge. I've screwed the old and new rafters together. The rafters are 3.385m at the shortest points, whereas those at the gables are 3.440m so there's a difference of 55mm to absorb.
The roof pitch is 40 degrees and faces south.
I'll fit the fascia board to the wall plate using spacers to give a 10-15mm air gap behind it.
With a 50mm tile overhang into the gutter, 20mm for the fascia board, 15mm air gap the maximum roof 'depth' (I'm not sure of the right term for that dimension? Can't be span, width or length..?!) would be 3440 + 85 = 3.525m
I'm re-using the old double romans, and will buy more. They're around 410mm long, with a few mm variance between different tiles.
If I've got this right, I calculate that a 90mm headlap means each tile will cover 320mm, so 11 rows will cover 3.520m
Q1: Is that right?
Q2: Is 90mm headlap enough for these tiles?
If I add an extra row of tiles, each tile will only need to cover 3.525/12= 293.75, say 295mm, which would give a 115mm headlap.
Q3: Would that be too much..? If not, is this better than 90mm? And is it necessary?
Q4: Is the batten gauge the same as the tile coverage, i.e. 320mm for the 90mm headlap / 11 rows, 294mm for 12 rows / 115mm headlap?
Q5: What's the best way to "absorb" the differences in rafter length / roof depth?
Many thanks, in anticipation, for responses..!
