At the end of my last post the builders had taken the old roof off and saved the tiles, which was a straightforward job. This changed the appearance of the house in a very dramatic way. There has been so much discussion leading up to it I thought it would never happen! But as with everything on this build, I would rather they go slowly and get it right than rush it.
The first job was to place two new metal Rolled Steel Joists (RSJs) across the top of the roof horizontally. This will form the basis of the roof, the position of all the Stecio joists will be determined by these RSJs. They do have to be insulated to prevent cold bridging, so are sitting on special insulating pads at either end of the building. I mentioned cold bridging in The Main Start of the Eco Build – Unbuilding and Ripping Down. As you can see, concrete blocks hold these RSJs in place. Each RSJ was bolted to the central metal pole.
The height of the attic floor had to be measured before anything was done, to make sure that the finished attic floor will be just below the base of the central vertical pole, and that the roof will be at the right height. This pole holds up the two middle ends of the RSJs.
We are going to raise the height of the roof by about 240mm to allow for timber Steico I beams. Then insulation will be put in between the I beams, exactly the same process as we will use on the back wall of the living room.
Timber Steico I beams are made up of natural fibreboard, which forms the upright bit of the I, and the oblong ends are made of LVL (laminated veneer lumber). This is formed of multiple layers of thin wood with adhesive in between the layers, it is a very robust material and doesn’t warp, or twist like wood can.
I beams are very eco: they use about a third of the amount of timber than if these beams were made of just ordinary wood. The joists are FSC certified (Forest Stewardship Council.) This organisation was established to promote responsible management of the world’s forests.
The I beams will run up the roof at an angle. Fitting these beams is an art in itself. They meet at all sorts of angles and have to have bits of wood to fill the gaps where they don’t quite meet, so all quite fiddly.
The architect needs to tell the builders exactly where to place each I beam, so that the fixings can be put at the correct intervals. This is important, as the big sheets of fibre board, called Gutex boards, that are going on top of the roof can be vulnerable to suction, when there are strong gusts of wind. So the fixings have to be exactly right so that I don’t lose the roof in strong winds!
As you can tell, quite a lot is going on at the moment, and after all that working out where straight is, in the last post, we now have the main structure of the roof marked out in Steico beams. Now we can get on with the rest of the roof phew!