Replacing a laundry room roof.
I live in an old house with a laundry room that was a much later addition. The laundry room is pretty small, and the roof for it is completely independent of the roof for the rest of the house. Recently, the roof started leaking, and I saw that the planks that had been used as decking had become pretty badly rotted.
This past weekend, I went up on the roof and tore off the old decking, with the intention of replacing it with plywood, and found a nasty surprise. The rafters are also pretty well rotted. I tried to patch it, and did enough to keep the laundry room dry for now, but I wasn't happy with it the way it was. It looks bad, and I know what needs to be done.
I figure the best way to deal with this is to put up new trusses and go from there. However, it's a small laundry room, about 7'x7' maybe, so I don't need a lot of material. While I've put trusses up on houses before (worked residential construction for a short time a while back), I've never had to figure out much else but where to drive a nail.
First question is, where do I need to measure? I figure I need to measure from the top plate to the peak, and probably the width of the room, but what else? The current rafters are notched to sit directly on the plate, and I'm not real comfortable doing that myself, so I figure to add a soffet for the overhang instead. This would also reduce the steep pitch the roof currently has.
I really appreciate any and all help you guys can give me!