Another joisty question...

[Pecanfan]

Hi all,

I've got another joist question that I'd appreciate a few comments on, totally separate to my various 'loft' posts.

Basically, in case you hadn't already read in another post, the back of our upstairs flat currently has it's exit to the rear yard downstairs, i.e. the stairs are inside the flat and eat up a fair portion of, what will become, our new kitchen. The plan is to move the door from downstairs to upstairs and bolt a new metal fire escape on the back of the house. I can then fit a new floor where the stairs used to be and all will be dandy.

Well, after a weekend of knocking various holes in walls to see how the joists run, this would appear to be the situation:-

obviously I need to somehow put a floor where the current staircase is, however I have a number of dilemmas:-

1. I can't disturb the existing floor joists since they support our downstairs neighbour's ceiling and I don't really want to be stung for a replastering bill.

1. Joist A would appear to be supporting half (?) of the weight of the current floor and ceiling via Joist B, so I don't want to put any extra weight on Joist A OR B, which rules out simply shoving some new joists in and hanging between the wall and Joist B.

2. Likewise, I can't really run a couple of longer new joists perpendicular to the existing joists, suspended between the back wall and Joist A, since again I would imagine Joist A would be supporting too much weight.

1. I can't up-rate Joist A with steel on the back, since there's a concrete floor behind it.

SO, the only thing I can think of is to do this:-

I'll install a temporary joist from the back wall to the concrete floor and fasten the existing joists to this using twisted restraint strap. This should provide enough support to stop the ceiling from collapsing while I remove Joist B. I'll then just bolt new joists to the existing joists and remove the temporary joist once everything is secure.

Can anyone think of any problems with this or does anyone have any better ideas?

All of the joists in question are 65 x 175mm and the span from left to right is 2370mm. I tried downloading SuperBeam but it makes no sense. :-)

As a side note, if a joist hanger isn't quite at the right height, which of course it will be, what's the best way of 'packing' between the joist hanger and the joist to bring the joist up to the perfect height? Slate?

Anyway, cheers again in advance!

Andy

[Christian McArdle]

What terms are you on with downstairs? They might be willing to let you (a) prop up the joists and (b) pay you some dosh, if you sell them the downstairs portion of the staircase.

Christian.

[Tony Bryer]

That all sounds quite sensible, although it would save time if your neighbour downstairs would allow some temporary propping while you removed trimmer joist B. Where you bolt the old and new joists together I would want to see large square washers under the bolt heads and nuts with double sided toothed washers in the join. The bolt size/spacing does need to be checked for adequacy.

Will you forgive me not adding this to the quotes on our website

[Pecanfan]

Well, not great. We've just moved in and they're moving out so aren't keen on me doing ANY building work while their house is on the market. On top of this, we're swapping the bathroom and kitchen over and they're not at all happy about having a bathroom above their spare bedroom (which is actually their main bedroom) - although it'll be fully soundproofed, damp-proofed and all plumbing will be running above the floor - and the alternative is a KITCHEN!! God damn it... Deep breaths...

By the time we've got planning and b.regs through for the new staircase we

*might* have some new neighbours who might be a bit more accommodating - having said that, we're considering using the underfloor void as some sort of beer storage area. :-) Having said that, some extra cash towards the refurb wouldn't go a miss!

Andy

[Christian McArdle]

Personally, I'd consider waiting, if the flat sale is likely to be imminent. However, I suppose the sale part could occur after your side of the conversion.

Christian.

[Pecanfan]

I've checked with our solicitor and we shouldn't need the freeholder's (i.e. the owners of the downstairs flat) consent.

Andy

[Tony Bryer]

Have you got the freeholder's consent?

[Set Square]

I think I would be looking to double up Joist B, rather than removing it - and then put some new joists from B2 across the stair void. What is the thickness and level of the concrete floor behind Joist A? Could you bolt A to the concrete, and thus make it able to support one end of B2?

As others have suggested, you may have some negotiation scope with the downstairs owners (new if not current) concerning what happens to the space currently occupied by the stairs.

[Pecanfan]

The concrete floor section is at the same level as the floorboards covering the joists. I have no idea how thick it is though. I also have no idea how it's held up so I'm slightly nervous about relying on it for support. It's a 1900's terraced flat and I didn't even know they had concrete back then!

Andy

[Set Square]

Have you asked yout tame structural engineer for advice?

[John Rumm]

would be tempted to strengthen A (and B if required) to allow you to do the more "natural" additon of new joists over the stairwell.

You may find that you could insert a temporary joist parallel to A but say 6" away from it, and then fix B to it. Then cut B a couple of inches short of A and insert a new joist beside A and bolt it to the existing A. Now rehang B back onto the strengthened A. If B is not up to carrying the extra load over the stairs then you could also double this at that stage. Finally hand the new joists over the stairwell from B to the wall.

[Pecanfan]

Not on this one (yet) - but if he comes out again to measure up for the loft I might pick his brains a bit more...

Andy

[Pecanfan]

Mmm... but, how can I insert a temporary joist parallel to A but 6" away from it without cutting B first (and our neighbour's ceiling falling down)? Or have I totally missed the point? :-)

Oh hold on, do you mean a temporary joist above the floor and strap it onto B to hold it up temporarily while I cut the end of it?

Wouldn't you still be relying on a strengthened Joist A to support 1/2 of the entire floor weight?

Andy

[John Rumm]

Yup - that is what I was thinking...

That is not far from the situation you currently have (looking at your original diagram) since the floor joists hang off B which in turn hangs of A - so A is taking half the full floor load, plus possibly half the stair load (the wall at the other end of B taking the other half of the floor load).

If you double the strength of A, then one ought to expect it would be able to take the additional weight of the other half of the floor. In reality it will not be as extream as "other half", since if your drawing is roughly to scale, thent the stair area is less than the existing floor area, and also you would be loosing the load of the stairs.

[Paul King]

Just as an aside, and after reading all of the posts in this thread...

I hope that you have adequate Public Liability Insurance!

If you start tinkering with the removal of these joists (even though you take adequate precautions etc.) and the ceiling caves in on the downstairs flat (hopefully while the people are out...) there'll be HELL to pay! If they're in at the time, you might have to pay the next-of-kin!!!

Also, as someone else pointed out - but I don't think you realised his point, are you the Freeholder of your flat? You can be the owner but not own the Freehold - in which case you are a Leaseholder. If you are a Leaseholder you will need to obtain the permission of the Lessor to make the alterations (which you prolly won't get), and if you do there could be a clause to "make good" before you sell - which means putting it back the way it was originally! That may prove difficult if you've already sold the staircase space.

[Pecanfan]

Surely you could say that for just about any DIY job? There's always an element of risk - you could plumb a bath in and flood downstairs, build a new fence and it falls on your neighbour's dog etc etc. ...and I'm pretty sure public liability insurance wouldn't be applicable in a case such as this. If I were employing builders to do the work *they'd* need to have public liability insurance.

It will also be physically impossible for the ceiling to cave in.

As I said, "I've checked with our solicitor and we shouldn't need the freeholder's (i.e. the owners of the downstairs flat) consent.". It's a standard terraced flat agreement whereby the upper flat owns the freehold to the lower flat and the leasehold to the upper flat; the lower flat owns the freehold to the upper flat and the leasehold to the lower flat. This agreement is in place to simplify maintenance between the two flats etc. It's not designed to wrap simple building work in red tape.

Andy

[Tony Bryer]

Well yes, but I would argue that this is not 'simple' in the sense that it does significantly alter your flat and if done wrongly would impact on the flat below. When you sell you will be asked whether you have made alterations and asked whether you obtained any necessary statutory consents and the freeholder's approval.

[N. Thornton]

I see a series of issues here.

Firstly the floor structure will presumably be covered by the party wall act, so if your neighbour doesnt want any work doing that will add a couple of grand of legal costs, plus dictate how you do the work, which can again add costs.

Secondly I dont like your propsed beam extensions at all. The wood thats there is sized for the half run, significantly bigger would be wanted for double the run. Also how you propose to tie the 2 might weaken the structure.

3rd I think it would really help to understand what the problem is: its not so much collapse, but sag. Wood can sag by a foot or more over a 20' run without breaking. Joists are sized to limit sag. Sag causes cracking of plaster ceilings, which are not very flexible.

Rather than try to extend the beams, which would certainly result in the ceiling breaking up, my first thought would be to remove joist B entirely (using temp support of course) and put new joists running full width alongside the old ones, without removing the old ones, and attach old and new securely together. BUT do not do this unless you consult a struc eng who says its ok in your particular case to do it, as it might not be.

There is one more issue: I dont know what size the joists are now, nor what build regs says about you doing this, but you might possibly find that to conform to BRs you'd need to put bigger wood in that is there presently. If you should get caught in this trap, theres always steelwork, flitch beams, hardwood, etc.

Regards, NT

[Pecanfan]

Thanks for the reply - please see comments below:-

Without getting into the technicalities of the Party Wall Act, I'm kind of hoping the neighbour doesn't object since the impact will be negligible. I will be serving notice under the act but, by my understanding anyway, the Act is more biased towards the owner doing the building work as opposed to the objector - i.e. even if they do object there's not a lot they can do about it without getting an injunction... I could be TOTALLY wrong here though so please, anyone, don't take this as gospel! :-)

As mentioned in the OP, the current joists are 65 x 175mm (2.5" x 7") - the same size as all the joists in the house, some of which span 3 or 4 times the width proposed. I'll probably eat my words, but I really don't see it as being much of a problem. Especially since there's currently a bath, toilet and sink resting on said joists and, following the building work, there will be nothing resting on said joists.

Erm... 'it would certainly result in the ceiling breaking up'... are you sure about this? Since posting this I've had building control and a structural engineer look over my plans and they can't see any problems with them!

Good idea, although I do think this is overkill for the particular scenario. In reality the worst that could happen is that the downstairs ceiling cracks a bit - and this *is* pretty unlikely. I can't see there being sufficient deflection to cause catastrophic failure of the ceiling.

I'm no structural engineer, but I'm pretty certain 7" joists are sufficient to span a 2.3m gap. :-)

Cheers for all the info though - much appreciated.

Andy

[Tony Bryer]

Well no, because the original post said "All of the joists in question are 65 x 175mm and the span from left to right is 2370mm." The joists are presumably that size because that's what was needed over the main rooms and they've used the same size throughout.