I built my two storey extension for 20% of builder's quotes

This site shows how - step by step from design to completion

Cutting In the Roofs

With the trusses in place and the gable walls built up it was time for me to cut the new roofs into the old by creating a series of diminishing rafters. The necessary timber had been estimated and supplied along with the roof trusses.

tile_removingMy first job was to remove tiles from the main house where the first roof would join. The tiles are plain 'Rosemary' style tiles. They were fairly easy to remove, but because they form a double overlap there are a lot of the little blighters. Lifting them and carrying them down from the roof on my own was a long, and not particularly fun job.

By using string lines from the trusses, I estimated where the roofs would join, and cut through the old battens. This was a bit scary as I was now messing about with the main house.












Working at a 40 degree angle makes everything more awkward. However, by setting the depth of cut right, and using my circular saw it wasn't too difficult.

I left a section of battens in the centre for the time being as they proved really useful to walk on to reach the apex.

I used a string line from the existing trusses and fixed a nail at the apex point. I then ran another string line from the nail to the eaves so that I could position and fit the layboards (you can just about make out the strings in the picture).

I believe that not all roofers bother with the layboards, preferring to simply lay the new rafters straight onto the old rafters.

Again, the central battens are left just for me to stand on for the time being.

I knew this part of the build would take me a little while. I decided, therefore, to ensure I only started cutting into the old roof when the weather forecasters promised me there was a good spell of dry weather ahead.

rain_roofIt rained! Big time rain - it really chucked it down. About 4am one morning I could hear drip, drip, drip. I couldn't sleep so my wife and I spent a less than fun night strategically placing buckets, pots and pans around the old loft.

I had covered the area in tarpaulin and plastic sheet as best I could but it was one of those windy, rainy nights where water will get anywhere!

The first rafter bottom chord in position. Hopefully the angles make sense now! The timber is vertical - it just looks a bit of weird angle due to my photography whilst standing on a sloping roof.

bottom_chordThe support block was there just to hold the timber in place whilst I measured and worked. The timbers would be nailed in due course.

The layout drawing that came with the truss design showed the position of the three diminishing rafters I would have to make. I measured the position of the first one against the layboards and cut the bottom chord timber.

I cut an angle on the bottom of the timber to match the pitch of the old roof, so that it would sit nicely on the layboard I had fitted. I also cut an angle on the ends of the timber to match the rafter angle of the trusses. (Hard to explain, but hopefully makes sense in context with the following pictures)

It was hard to photograph the diminishing rafters as all the trusses get in the way. This pic should give the idea, however.



angleI fitted a ridge board from the last truss to the apex where the layboards meet. I then fitted three diminishing rafter made up of a bottom chord and two rafters that fix to the ridge board.

I used a long straight edge laid along the trusses to ensure my diminishing rafters were in line.

I then fixed two vertical timbers from the mid point of each rafter to the bottom chord below, to help take the load (as prescribed on the truss design drawings). I also fixed some angled bracing across the diminishing rafters.


cut_valleyIt's hard to make out from the pic because there are so many pieces of timber.

I have two roofs that need cutting in, so having done one, I just did the same all over again (but a bit quicker).

Next I would need to deal with the box valley gutter before I could even felt and batten. In the meantime I covered everything in tarpaulin (courtesy of Freecycle). It kept things dry, by and large, but the rustling noise gets annoying in the wind.