Joists for a loft conversion?

[york33]

Hello!
I'm hoping for a bit of advice re. a loft conversion. I'm just at the stage of figuring out how to do it, what to get others to do for me, how much, etc!

Whilst I've got a good idea of most other areas, an outstanding issue is the new floor. Whilst I'll probably get a carpenter to actually put them in for me, I'd quite like to get it straight in my head what I need them to do. I had initially assumed I would get new joists laid from the front wall through to the centre wall of the house and then the same again to the back wall.

Having had a dig round the eaves I've realised this may be rather tricky. Above the front and rear walls there is only a few inches clearance between the top of the wall and the slates. I'd initially thought perhaps cutting the ends of the new joists at a slight angle or removing a corner would allow them to fit in. However, it looks like this would remove so much 'meat' from the joists it would seriously weaken them?

So what to do to get round this? I assume this is a common problem? My inexperienced head thinks I'd either have to lower the ceilings below, eek! Or install a rather large trimmer (if that's the right word) between the two side walls of the house (about 15ft) and hang the new joists off that?

Thanks in advance for any thoughts.
Dave

 

[noseall]

What is the pitch of the roof?

 

[york33]

Thanks for your reply, if I've got my trigonometry correct, bearing in mind I've not done any for 10 years It's approx 33 degrees.

 

[dextrous]

Probably worthwhile using a couple of steels as your "trimmers" and hanging joists off this. Whatever you do, it will no doubt require structural calculations, LABC involvement and local planning permission. Probably worth getting an architect round to assess the preliminaries for a few hundred pounds, I'm afraid.

 

[york33]

Thanks for the reply, I was getting suspicious I'd be heading the way of steels in there. Would I be right in thinking a structural engineers report is needed when things like that are involved?

You mention planning permission? That shouldn't need to be involved, unless I've missed something? Building control will be involved anyway as I want it as a proper room.

 

[Chukka63]

depends if youre building outside the current roof line as far as im aware.you will need calcs.

 

[york33]

Everything's contained within the existing roof line, only real external difference is 2 Velux

 

[dextrous]

Everything's contained within the existing roof line, only real external difference is 2 Velux

LABC will want calculations for any alterations to the structure of the house - supporting a couple of steel beams on the existing walls will no doubt be considered to be adding weight etc etc. They may even want specifications regarding any padstones that may be required to rest the beams on, or any alternative method of supporting them. The structural engineer will be able to work this out and advise. He'll also be able to advise on any strengthening od the existing rafters for the velux windows and the weight of whatever plasterboard you'll be adding. Insulation, means of escape etc etc are often overlooked.

If you're going to do it right, it's worth spending a bit getting the specs all written out - then at least you know what your LABC will be happy with.

It's worth a phone call to the planning department to ensure that what you have in mind doesn't require any formal submissions to them. Just to be on the safe side.