Hi,
I'd be really grateful for some opinion on my roof, because I'm clueless when it comes to structures made of random bits of wood nailed together...
formatting link
a diagram and supporting photos...
It's been like this for 30 years ish, except for the stairwell which was altered maybe 8 years ago. However, the overriding question is:
Is anything there dodgey (I think possibly)? If so, now is the time to fix it, not in 2 years when I've redecorated and fitted the place out(!) ;->
Ultimately, if it should be fixed, I'd rather fix it. If I'm worrying unnecessarily, then I'll leave it.
The specific things I'm concerned about:
a) Dodgey bearing plates?
In the photos 2,4 and 5 we see the correct approach to strengthening the floor (blue joists on diagram). Clearly, there's a wooden plate on top of a single brick centre wall. This looks OK to me. Other ends of joists sit on plate on perimeter wall (inner leaf of cavity wall).
But, in pictures 6 and 7, we see that the joists seems to be sitting on the plasterboard that makes up the ceiling below. I've poked it with a screwdriver and it's plasterboard alright, and there is definately something solid and hard under it (brick in all expectation).
Why anyone would do this is beyond me. I would have though it would be harder to work a full sized sheet of PB in there whilst jugging joists on top, compared to just putting in a wooden plate, fixing joists, then fixing PB.
It doesn't look like it's compressing, but should it get wet I suspect the floor upstairs might go down 10mm in a hurry.
In order to fix, I'd have to take a section of PB out from below, dig and clear the top of the wall and slide a bit of wood in. Not a stupidly difficult job, but it's more work and I'll mess up an otherwise OK ceiling.
I believe the affected areas are where the centre wall is marked yellow in the diagram, though I haven't verified all of it.
Panel's option - should I fix it?
b) Roof tie
In the last two pictures, is the beam marked by red text a "roof tie", designed to stop the roof spreading apart? At first glance I though so. But I'm not sure. Originally, as indicated by the purple lines on the diagram, there were two, at about 1/3 and 2/3 spacing. They've been cut where the dormer is, so I'm not sure how effective they are. Probably relying on being nailed (maybe!) to the dormer frame.
Not really very easy to fix, probably need to put tension bars in threaded steel through the middle of the 8x2 joists.
Should I worry?
c) The original question of inserting 8x2 joists in the alcove areas. Seems I can't easily do this without cutting the "tie beam" (or whatever it is) back further, which scares me a bit.
I ran up Superbeam earlier and assuming the 4x2 joists are C16, I reckon, over a 3.4m span, each one would take a load of about 40kg before deflecting 14mm. I'm not smart enough to make allowances for the extra 4x2 on top spreading the load. I'm >100kg (fat b*stard) and standing on a single joist doesn't seem to cause perceivable deflection. Maybe they are better than C16 and perhaps the frame of the dormer is tying them together.
I would envisage putting maybe 300-400kg of load in the alcove on the bottom left of the diagram in the form of books and tools plus me.
Should I worry?
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All of the above can take a tristate answer of yes, no, ask the BCO. I can ask the BCO to have a look first time he's there, but one is always mindful of the "let sleeping dogs lie" addage :) However the BCO is likely to get an eyeful when I get to the re-insulate-the-roof phase in 18 months, so that would be a very bad time for him to notice lots of stuff he wants fixed...
Many thanks indeed for your thoughts.
Cheers
Tim