I am currently at the planning stage with my proposed loft conversion which I intend to carry out myself. I have plenty of trade experience as I am an electrician but am unsure of a couple of aspects regarding some of the building regs. My primary concern at the moment is the hanging of my new 9x3 joists for the loft floor. I would like to hang them from joist hangers which will be set directly into the brickwork of the external wall on one side and the same on the other side at the internal party wall. I need to know if the regs allow me to cement joist hangers directly into the masonry, and if so do they also have to be bolted in. I've tried to find this out from books and on the internet but all the photos I've looked at involve fixing a timber beam to the wall first and then hanging the joist hangers from it ??
Also can I get double joist hangers somewhere for where the joists have to be doubled up under the stud and purlin walls, or do they have to be fixed directly into the masonry....I can't seem to find big enough joist hangers for this ??
Joist hangars for mounting into masonry do exist, they are alot more rigid than the flimsy ones that you fix to timber with.
Can you not fit 2 side by side for the doubling up?
I dont think that these joists have to be absolutely tight together, but mus be bolted together to stop them movig apart.
I've bought some BS6178 225x75mm masonry joist hangers from screwfix so that problem is solved at least.
Regarding the doubling up question, if I put 2 single hangers side to side in the masonry it's going to mean that there will be a gap of around 2-3cm between joists which I don't think will be acceptable for the spec, especially under the purlin walls which are going to play a significant part in holding up the roof. I checked another couple of websites yesterday and apparently special sizes of hanger can be made to order which might be a solution for me if I can't find anything else. So far the widest ready made hangers I have seen are 150mm which is good, but they have only been 150mm deep which is no good at all.....I'll keep looking and post again when I have an answer.
as a sparky too who sometimes does building works, I would get B Control out and ASK them for their advice. They are in my experience very helpfup, and keen to solve problems, and in the end it is they who sign the work off if you ever want to sell.