Stupid idea for Loft floor

[PaulBB]

Hello, new to the forum but hoping to get some feedback on this idea.

Currently in my house (a 1900 built terrace) I have an office / workshop / dumping ground for all the half finished projects I have going on. Unfortunately, due to my wife deciding to go and get pregnant (I may have helped here) I'm about to be removed from said office, which is being turned into a nursery.

So...the loft. Currently the joists are pathetic, the ceilings in the upstairs rooms all bow in the middle, and I worry if I stand on any of them they'll give way. We also don't have quite enough height in the loftspace to put a new floor in up there (there's about 2m from the top of the joists to the bottom of the...big timber that goes across the roof pitch...which is annoying because the bedrooms all have about 2.9m ceilings.

Currently the joists run from the front wall of the house to a central wall that runs between 2 bedrooms, then from that wall to the back wall. middle wall to front is about 4m, middle to back is slightly longer at about 4.5m

I can't really afford a full loft conversion so, here's my dumb idea:

I'm going to use resin bolts to mount wall plates onto the frontwall, back wall and both sides of the middle wall. Then use joist hangers to run 9*2" timbers directly under each of the current joists as tightly up against the celiling as I can manage. Then board over the new ceiling and in the loft put loftboards over the existing joists.

I'm not expecting that to meet any kind of building regs, but it should be reasonably solid to walk around on I think? I won't have anything heavier than a desk up there so I'm hoping it should take the load.

Any thoughts? Really stupid idea?

 

[Dereekoo]

We also don't have quite enough height in the loftspace to put a new floor in up there - but that is what you are doing?

under each of the current joists - how can they go under the current joists?

I won't have anything heavier than a desk - in that case size of joists could be reduced depending on centres

 

[PaulBB]

how can they go under the current joists?

By working out where the current joists are and putting new joists under them. There will be the ceiling in between them obviously but so what, the new joists will still support the old ones

 

[StephenStephen]

An amateur suggestion: why not sister the existing joists?

 

[PaulBB]

Because the new joists are deeper than the existing ones by some margin, so I'd lose head height in the loft.

 

[StephenStephen]

Because the new joists are deeper than the existing ones by some margin, so I'd lose head height in the loft.

Yes - I'm wondering if the span calcs show that they need to be deeper?
There's also the question of how to get new joist up into the loft, if you go that route...

 

[PaulBB]

Yes - I'm wondering if the span calcs show that they need to be deeper?
There's also the question of how to get new joist up into the loft, if you go that route...

Yeah they'd need to be significantly deeper, I'd lose at least 6 inches in head height and it's already only just bearable.

Getting 4m long joists into the loft is also a consideration, this way I don't have to worry about that

 

[foxhole]

What are the dimension side to side? To run across under loft timbers?

 

[PaulBB]

Maximum span is 4.5m

 

[Dereekoo]

how can they go under the current joists?

By working out where the current joists are and putting new joists under them. There will be the ceiling in between them obviously but so what, the new joists will still support the old ones

Gotcha, didn't twig that new joists are going under existing bedroom ceilings, must read more thoroughly.

As an aside what are the dims of the existing ceiling joists and what are their spacing

 

[PaulBB]

dims?

Pretty sure they're 400 centres

 

[catlad]

I wouldn't try lining the new joists up under your old ceiling, I'd do it perpendicular to your existing ceiling ties.

 

[PaulBB]

I thought about that, but there's a stud wall down the middle of one room. If I go perpendicular I'd have the stud wall at one end of the new joists.

 

[robinbanks]

I think it could make for quite a nice decorative feature to have the joists on show in the rooms below. Not so sure about the ends though; joist hangers look gash but you might get away with a ledger under. Could always then later improve the insulation with 50mm all round to hide the ledger

Easy to drill a small hole at 45 degrees in the ceiling alongside an existing joist to help locate the one below, and then the installed joist hides the hole

Are you fitting a staircase or just using a decent loft ladder?

 

[PaulBB]

Just a loft ladder, given the lack of enough height in the loft to comply with building regs this is just for storage your honour.