Another loft question sorry ‍♀️

[Jake2021]

Hi all
Apologies another loft question… thanks to the guys on here I finally have sockets and lighting in my loft

It’s not going to be a loft conversion as I don’t have the height but I will be boarding it out for storage as we have no storage in the house

I was planning on removing the roof tiles and threading some new joist through as I thought the stud walls in the bedroom weren’t supporting however when I’ve removed the insulation in the loft the joists are actually two overlapped resting on the walls which is going to save me a ton of work and money!

anyhow what size joists would people recommend please I was thinking 6x2, 6x3 or 7x2…. Each length of joist at the moment is 4x2 approx 7-8 metres( in two pieces joined) the supporting wall is approx 3.5 metres from one joist end.

would it be best to put the new joists up to the old joist and screw them
Together and bolt the overlaps or keep a gap between the old and new joists along the length
?

inhave also been thinking about the rafters for some reason I have in my head they need to
Be 6x 2 and not the current 4x2 would
It be best to put some 6x2 bolted to each rafter for the insulation? I could if just made this up though

I really appreciate any help and advice anyone can give and thank you in advance
Thanks
Jake

 

[Deleted member 174758]

Lapping joists which are just carrying a plasterboard ceiling is quite common, but a ceiling is fairly light and doesn't require a structural stud wall to support it. You'll probably be OK with light loads on a standard stud wall, but if you intend to put a lot of weight up there you'd be best off checking the structure of that wall as it may not be syrong enough to carry a large amount of weight

Modern structural stud walls are supposed to have doubled-up sole plates and headers as well as (sometimes) doubled-up studs. Victorian and Edwardian structural stud walls often have heavier door frame studs, are often notched into the (heavy section) sole plate/header or can even be mortise and tennoned and in addition you sometimes get diagonal braces halved (halving jointed) into the studs, to boot. One thing about these old time builders, though, is that like modern builders they wouldn't put in a more expensive structural stud wall when a cheaper non-structural one would do

 

[cdbe]

For my money, the best way to do this is to install 2x timber beams of 8x2 bolted together and hung off the party walls from masonry joist hangers, about 750mm in from the eaves. You could install a third beam above the central stud wall if you're concerned about its ability to carry the extra load.

Hang 4x2's off the beam with Jiffy hangers, above the existing joists, this will give you 200mm to fill with mineral wool insulation. Place 50mm or ideally 100mm celotex on top of the joists and then lay your boarding on top - doesn't need to be thick as the celotex will support it - thin plywood or OSB.

Your focus should be on maintaining or improving the insulation when doing this project.

Trying to get joists onto the wall plate is a nightmare to be avoided.

You don't need to do anything with the rafters.

To avoid pulling tiles off the roof to get timbers in, consider going through a bedroom window and cutting a bit of ceiling out - not difficult to make good afterwards.

Here's mine, slightly different because I had the ceiling down and scrapped the existing joists etc but should give the general idea.

 

[jks7492]

For my money, the best way to do this is to install 2x timber beams of 8x2 bolted together and hung off the party walls

And then open a whole can of worms with party wall agreements just for the sake of boarding a loft for a bit of storage?..

 

[jks7492]

I'd run some larger joists alongside the existing ceiling joists and screw the two together

 

[cdbe]

And then open a whole can of worms with party wall agreements just for the sake of boarding a loft for a bit of storage?..

Party wall, for a couple of joist hangers, I wouldn't be bothering with that nonsense.

 

[Jake2021]

Hi all ,
Many thanks for everyone’s input so far…
Cdbe, I didn’t realise you could bolt two timbers together and place into the party walls
would the timbers go into a cut out into the party wall or would you bolt a piece of timber along the party wall the put hangers on for the 8x2’s(8x4)
How much over hang would need to go into the party walls if they go through the wall?

The other way would be as his said and bolt the joists together… would this still sit on the wall plate timbers?

insulation is one of the reasons I want to do it as we have very little up there at present but also storage, we have a fair bit of stuff to store and as it is at present I wouldn’t want to put it up there lol

many thanks for your help guys

 

[cdbe]

Use masonry joist hangers, remove the mortar from a joint, insert the hanger and fill back in.

You could sister (bolt new joists to the existing) and they wouldn't necessarily have to extend all the way to the wall plate as the issue is usually bending mid span.

As you've identified, the main focus now should be on super effective insulation - 300mm mineral wool (or the equivalent) over the entire loft area so you need to consider where it's going in your design - compromise and it'll cost you a fortune in gas over the next few years.

 

[Jake2021]

Cdbe,
Many thanks again… you’ve hit the nail on the head re gas as it’s one of my priorities of doing it but thought since I’m doing insulation I may as well have a decent flooring and joists, just seemed logical‍?

I thought this time of year would be a good time to do it as it will be getting better weather and will be finished when I need the heating again if that makes sense? It will just be hot working up there lol thanks
Jake