query on loft conversion (pic supplied)

[stuartmorrell91]

Hi,

The 2 pictures below is of the 3rd floor of a 3 story victorian terrace that we have just bought. The original construction was quite weird where they have halved the room with a bedroom leading through to a small loft space through a door, so as you can see i have knocked the wall down to use the loft space.

Now the problem. The bedroom half of the construction has 7" joists, but the loft side has 3" joists, which makes sense as it was just for storage.

Now my theory to make it work. Would bolting 2 long wall joists either side of the brick wall, and then bolt onto them wall joist hangers and go across the existing 3" joists with timbers to bring the floor up level work? or does the new floor have to sit above the 3" joists so it doesnt touch them?

I am only needing to raise about 6 feet of the floor up, as i'm building cupboards under the eves so that can stay at 3".

Any help appreciated.

 

[syne]

Now my theory to make it work. Would bolting 2 long wall joists either side of the brick wall, and then bolt onto them wall joist hangers and go across the existing 3" joists with timbers to bring the floor up level work? or does the new floor have to sit above the 3" joists so it doesnt touch them?

You mean wallplates/ledger board with joist hangers, then add(sistering) a 4"joist to the 3" to make it up to the same height throughout.

You could.. but you'd probably find it likely to crack the plaster on the ceilings below when you add weight on the new floor.

Look at the trada span table, for a joist size suitable for the spans/loading, it'll not be a huge joist for that sort of gap.
It should be possible to leave the existing 3" joists completely untouched,
and still put new joists in between those, still leaving a gap for deflection above the ceiling below.

 

[stuartmorrell91]

Hi, Posted this in September as per text above. Basically it's a 3rd floor bedroom that i have knocked down the partition wall to extend the room, but the joists on the loft side are only 3", bedroom side 7".

I've posted a crude picture of how i'm going to do it below this weekend. I've used the span tables so the joist sizes should be correct, my only concern is, if you look at the drawing (in red) i plan to fit supports from the roof purlin to the 7" supporting joist, would this be ok? It may take a little of the weight of the joists and the cupboards, but i need the supports to build cupboards off.

Would this work, or is securing to the purlin a no no?

Any help appreciated.

 

[noseall]

No, don't use the purlin.

Can you not use the roof wall plate as one of the support for the joists?

 

[stuartmorrell91]

I looked at tying to use the wall plate but can't with resting wood on the existing joists. The purlin is 11" thick over a 3 meter span, which in today's construction sizes I believe is oversized so I was hoping it would cope. Looks like I'm back to the drawing board.