Any structural engineers/architects on the forum?

[NafemanNathan]

Do we have any structural engineers/architects on the forum that would be happy to give some advice on loft conversions? I've got a potential problematic loft space, and a potential solution, but want to know if it's the only solution

Cheers

[bennyboy]

I'm not, but I'm doing the same thing Got the paperwork back from the council just yesterday in fact.
Fire me a PM with details if you like, perhaps it's something I've discussed throughout the process of mine, or I can give you my Structural Engineers contact details.
He's a helpful guy, and whilst not local to you, he may be able to answer your q's without a visit?

[NafemanNathan]

Cheers Ben. I may as well post it on here as other members may also be able to chip in...

Basically I want to be able to do as much of this myself as I can, mostly to keep the costs down, partly because I enjoy DIY, partly because I like a challenge and partly so I can avoid working on the Prelude

I was hoping it was going to be fairly straight forward. I know where I want the staircase, space and headroom is spot on. Nothing is too cramped. I'll lose a teeny tiny bedroom on the first floor, but gain a very good sized landing/study and a huge very nice sized double bedroom or two bedrooms in the loft (for the boys).

The existing ceiling joists are 5x2", so need to be upsized as they're obviously not strong enough. The existing joists will have to remain, so I don't have to tear down the ceilings below, so new joists will have to go in in addition. I don't have a size yet, but they'll most likely be 8" tall to allow for the correct depth of insulation. They'll also be raised off the existing ceiling so as not to damage it.

... My issue though is that my wallplates are a lot lower than my joists. The rafters sit on the wall plate and the joists are tied into the rafters (A Collar-Tie roof I believe it's called).

This is my loft space (Exactly )...



The dark grey along the base is the wallplate.

So, if I was to put in larger joists, I'd also need to tie these to the rafters, but with the existing rafters only being 4x2" they too will need to be upsized/doubled up in order to take the extra load!

Being new rafters will also need to sit on top of the wallplate (Else what's the point?), the only way I see that happening is if all the tiles, felt and battens come off

I do want the roof re-tiled at some point anyway, plus I want the larger chimney stack removed and a few velux windows put in on one face, but new rafters just adds more time and costs that I was otherwise hoping to avoid.

Can you see any other way around it?

[bennyboy]

No.











Sorry!

Ours is a cheap truss roof - it was built under Housing Association (read: lowest bidder for the council...)
I have a builder doing the 'watertight exterior box'/dormer etc and my brother and I will be doing everything inside, staircase, walls, blah blah.
We're putting three steels across and strengthening the joists and roof, same as you My brother did at one point say he was tempted to just build me a new roof

I certainly can't think of another way to what you have mentioned, as if I'm not mistaken, it's the act of actually getting the full length rafters and joists into the void isn't it? Unless it would actually be easier to go up through the ceilings and replace them? Just plasterboard and a skim after all. OK, I know I'm simplifying it a lot, but compared to essentially de-roofing and re-roofing etc it may be cheaper/quicker?

[Tombomb]

I'm a builder nafeman but no engineer buy any means .is that your actual roof drawing my bros an joiner he dose these all the time . I'm nearly sure their is other ways around it il run it past him here to c wat he thinks

[Sailor]

What are the length x width dimensions of the basic floorplan? And what are the current rafter & joist pitches?

[NafemanNathan]

@Bennyboy. Even removing the ceilings below I still wouldn't be able to get the rafters down between the wallplate and the underside of the roof. Possibly if the rafters were in two halves and then sleeved back together.

@Tombomb. Yep, that's my exact roof layout

@Sailor. The floor pan (so inside of rafters is approximately 4920x7770mm. The joist/rafter centres vary most commonly between 400 & 440mm.

[Tombomb]

Nafeman it looks like on your drawing that it roof truss has a small votic ceiling ,witch means that your wall plate is lower than your ceiling joist so u would not be able to rest the new support joist in unless you drop the ceiling height in your house . Going buy that drawing lad

[NafemanNathan]

That's exactly right Tom.

[simonc]

Another building project Nathan?