can joists overlap between bearing walls?

johney

hello folks, doing a shed which will have an upstairs relax room. Can joists overlap between two load bearing walls? The lap will be long however. My issue is the joist were ordered quite a while ago and now the supplier will not exchange them. The joists are 4.8 metres. The span is 4.2 metres to each nearest wall or 5.2 metres to each furthest wall. I am not sure what to do?

Thanks for your kind thoughts.

Petyr Baelish

johney wrote: »

hello folks, doing a shed which will have an upstairs relax room. Can joists overlap between two load bearing walls? The lap will be long however. My issue is the joist were ordered quite a while ago and now the supplier will not exchange them. The joists are 4.8 metres. The span is 4.2 metres to each nearest wall or 5.2 metres to each furthest wall. I am not sure what to do?

Thanks for your kind thoughts.

What has the 4.2m got to do with it? I don't understand, do you have an option to make it 4.2 or 5.2 or does it vary?

I would be very cautious about lapping the joists, you would need to bolt them together at fairly tight spacing, or maybe use pressed metal brackets. One option that could help you would be to use pressed metal joist hangers so that you don't need to bear onto the wall and thereby shorten the span.

What depth are the joists? Have you had them designed by an engineer taking floor loadings into account? If not, you should.

Lumen

In general, joists should run perpendicular to the ridge to tie the walls together, and should be continuous from wall to wall.

Since they are in tension as rafter ties, they could probably cope with being lapped, but if you're putting a floor on them that's going to add an opposing load, and you're in dodgy territory.

Also, aren't you going to have to double them up, thus requiring more wrong sized timber?

johney

lads thanks for the replies and I am sorry as I did not explain very well. There is a 1 metre wide corridor running down the centre of the building. The joists lap right over this corridor. So each joist has a supporting wall 0.5 metre from the lap(opposite walls of corridor). And the lap is almost a metre, but not quite. Many thanks, john.

Calahonda52

johney wrote: »

lads thanks for the replies and I am sorry as I did not explain very well. There is a 1 metre wide corridor running down the centre of the building. The joists lap right over this corridor. So each joist has a supporting wall 0.5 metre from the lap(opposite walls of corridor). And the lap is almost a metre, but not quite. Many thanks, john.

you need to go again.
what about uploading a sketch photo from ur phone

muffler

If the joists are properly sized and overlap by a minimum of 450mm then I wouldn't see a problem.

Calahonda52

muffler wrote: »

If the joists are properly sized and overlap by a minimum of 450mm then I wouldn't see a problem.

It this what he has in mind, if so just get additional timber to span the corridor?

sketch ignores corridor wall thickness

Lumen

johney wrote: »

lads thanks for the replies and I am sorry as I did not explain very well. There is a 1 metre wide corridor running down the centre of the building. The joists lap right over this corridor. So each joist has a supporting wall 0.5 metre from the lap(opposite walls of corridor). And the lap is almost a metre, but not quite.

What's stopping the roof from spreading?

my3cents

Calahonda52 wrote: »

It this what he has in mind, if so just get additional timber to span the corridor?

sketch ignores corridor wall thickness

Thats the way I imagined it and thought simplest thing to do would be to bolt the over lapping ends together, so they make one long piece, which also deals with Lumens question about the roof spreading.

Calahonda52

my3cents wrote: »

Thats the way I imagined it and thought simplest thing to do would be to bolt the over lapping ends together, so they make one long piece, which also deals with Lumens question about the roof spreading.

Is this not the first floor so he can tie the wall at the wall plate level?

my3cents

Calahonda52 wrote: »

Is this not the first floor so he can tie the wall at the wall plate level?

I assume so, but Lumen seemed concerned about it so why not answer both issues?

It is a shed so I'd want something stopping the outer walls being forced out. But we have no idea how the roof will be framed and the roof structure might allow for the upstairs relax room without the need of the walls being tied together.

Lumen

I'm just saying



But I don't know whether that's what we're talking about.

my3cents

Lumen wrote: »

I'm just saying



But I don't know whether that's what we're talking about.

I don't know why the OP doesn't cut the ends off if he needs shorter joists?

Even if they are the modern fabricated I shaped wooden beams you can still cut them.

bfclancy

my3cents wrote: »

I don't know why the OP doesn't cut the ends off if he needs shorter joists?

Even if they are the modern fabricated I shaped wooden beams you can still cut them.

he doesn't need them shorter the issue is they are not supported at the very end of the joist rather they are resting on dividing walls and they overlap in the middle above the hall. i don't believe there should be an issue, why the concern over roof spreading i assume the joists will be fixed to the wall plate?

Petyr Baelish

Just join them together securely where they lap so they act as a tie. Maybe strap them onto the walls too.

my3cents

bfclancy wrote: »

he doesn't need them shorter the issue is they are not supported at the very end of the joist rather they are resting on dividing walls and they overlap in the middle above the hall. i don't believe there should be an issue, why the concern over roof spreading i assume the joists will be fixed to the wall plate?

I don't see why they can't just be joined at the overlap?

Lumen

my3cents wrote: »

I don't see why they can't just be joined at the overlap?

Right OK, if they're each resting on two walls capable of bearing vertical load, the main other load to worry about is tension, which is solved by bolting them together at the overlap.

muffler

Plenty of advice and "theories" being offered but the OP hasnt addressed the issues raised. Im not sure how anyone is expected to give a decent bit of advice without knowing the full set up. A photo or a sketch would have sufficed.

mikeymouse

Two 3m lengths bolted together using these lads,would give about 500mm overlap and plenty bearing on the walls. 4 or 5 bolts staggered at each overlap.
Might be cheaper to buy new timbers!

my3cents

mikeymouse wrote: »

Two 3m lengths bolted together using these lads,would give about 500mm overlap and plenty bearing on the walls. 4 or 5 bolts staggered at each overlap.
Might be cheaper to buy new timbers!

[Ridiculous Speculation] But what if the OP is using Engineered I joints ?



[/Ridiculous Speculation]

mikeymouse

my3cents wrote: »

[Ridiculous Speculation] But what if the OP is using Engineered I joints ?

[/Ridiculous Speculation]

Indeed, not enough information.

johney

lads, thanks for the replies, ye are very generous with the info. Calahondas sketch is spot on, but for 1 difference. The overlap in the middle is longer. In fact, it's almost the width of the corridor, just an inch or 2 short of the entire width. The span is actually approx 3.85 metres. The overlap is approx 950mm, but as said, while the lap is long and I can bolt the joists together, the only issue is the lap is not on any bearing wall, which I always thought was a necessity, at least in a house. Thanks a lot.

muffler

johney wrote: »

Can joists overlap between two load bearing walls?

johney wrote: »

the lap is not on any bearing wall,

Which is it - load bearing or non load bearing walls or something else? Maybe Im reading that wrong.

This is where things fall to bits in every sense of the word when conflicting info is posted.

my3cents

muffler wrote: »

Which is it - load bearing or non load bearing walls or something else? Maybe Im reading that wrong.

This is where things fall to bits in every sense of the word when conflicting info is posted.

I read that to mean the ends of the beams are in mid air and not bearing on a wall at all.

mikeymouse

muffler wrote: »

Which is it - load bearing or non load bearing walls or something else? Maybe Im reading that wrong.

This is where things fall to bits in every sense of the word when conflicting info is posted.

I misunderstood that too, until I looked again a Calahonda's diagram.
The way I see it now is the overall width is about 9mtrs,with a one mtr corridor running down the centre,so the span from external wall to first corridor wall is 3.85mtrs , and 4.85 mtrs to the other corridor wall, meaning the first joist rests only on the exterior wall and one corridor wall, allowing for a 100mm bearing on the external wall it will project about 850mm across the corridor, but not reach other wall of the corridor.The 2nd joist will rest on the opposite exterior wall and the opposite corridor wall,They will overlap over the corridor . so of the 4 walls, each joist will rest on 2 walls only.I can't see anything wrong with bolting them together assuming my assumptions are right(you know what the say about assumptions)
A diagram would paint a thousand words, but unfortunately I can't do at the mo.

muffler

my3cents wrote: »

I read that to mean the ends of the beams are in mid air and not bearing on a wall at all.

That makes sense

Are we sure that the joists are supported on the wallplates and tied to the rafters or are raised wallplates in play?

johney

muffler wrote: »

Which is it - load bearing or non load bearing walls or something else? Maybe Im reading that wrong.

This is where things fall to bits in every sense of the word when conflicting info is posted.

Its not conflicting.The lap is not on a load bearing wall as its "between" load bearing walls

mickeymouse and my 3 cents, ye get it and are spot on. All joists resting on wall plates and mid bearing walls. Both corridor walls are bearing walls. Overlap is about 850mm and it occurs in midair between the 2 corridor walls.

.thanks a lot to all of you and thanks for your opinions

mikeymouse

Calahonda52 wrote: »

It this what he has in mind, if so just get additional timber to span the corridor?

sketch ignores corridor wall thickness

This would then be a belt and braces job alright

policarp

johney wrote: »

hello folks, doing a shed which will have an upstairs relax room. Can joists overlap between two load bearing walls? The lap will be long however. My issue is the joist were ordered quite a while ago and now the supplier will not exchange them. The joists are 4.8 metres. The span is 4.2 metres to each nearest wall or 5.2 metres to each furthest wall. I am not sure what to do?

Thanks for your kind thoughts.

If the joists overlap over a 1 metre corridor and they are part of the roof structure, they must be triangulated. That is that the roof must be in the form of a triangle. Therefore over the corridor they should be bolted together where they overlap. If that makes sense.

johney

how many bolts at the lap might suffice?

Calahonda52

policarp wrote: »

If the joists overlap over a 1 metre corridor and they are part of the roof structure, they must be triangulated. That is that the roof must be in the form of a triangle. Therefore over the corridor they should be bolted together where they overlap. If that makes sense.

Has OP confirmed if the timbers in question are first floor joists or ceiling joists?

my3cents

Calahonda52 wrote: »

Has OP confirmed if the timbers in question are first floor joists or ceiling joists?

I took it to be one floor and a roof space because he said it was a shed, because I don't know of too many two story sheds.

my3cents

johney wrote: »

how many bolts at the lap might suffice?

I think I'd probably only use one say m12 but with large washers on each end and a timber connector on the bolt between the timbers. I'd also put in about eight 5 x 120mm screws.

But imagining the size of it all three bolts with washers and connectors wouldn't be out of order.

Timber connector

Lumen

Scarf joint?

https://www.youtube.com/watch?v=SUtoKKNKHQ

Calahonda52

my3cents wrote: »

I took it to be one floor and a roof space because he said it was a shed, because I don't know of too many two story sheds.

I prefer ABC
Assume nothing
Believe nothing
Check everything.

johney

my3cents wrote: »

I think I'd probably only use one say m12 but with large washers on each end and a timber connector on the bolt between the timbers. I'd also put in about eight 5 x 120mm screws.

But imagining the size of it all three bolts with washers and connectors wouldn't be out of order.

Timber connector

Thanks my3cents. You seem to get it.
Appreciate the reply

Lumen, that link will not play.

Thanks anyway.

Lumen

johney wrote: »

Lumen, that link will not play.

Oops.

https://www.youtube.com/watch?v=-SUtoKKNKHQ

my3cents

Lumen wrote: »

Oops.

....

Opps again :mad:

Video unavailable
Watch this video on YouTube.
Playback on other websites has been disabled by the video owner.

Lumen

Crap!

https://www.youtube.com/watch?v=-SUtoKKNKHQ

listermint

my3cents wrote: »

Opps again :mad:

Video unavailable
Watch this video on YouTube.
Playback on other websites has been disabled by the video owner.

Just click the YouTube icon and it will open the app .......

my3cents

Lumen wrote: »

Crap!

https://www.youtube.com/watch?v=-SUtoKKNKHQ

Good video worth watching.