How many Props to support a wall?!
Discussion
Taking down the ground floor cavity wall and inserting a steel & padstones so need to prop up the floor and 1st floor. Length of wall being removed is 3.2m, above it is a single skin brick which is a minor load bearing wall - takes a small amount of the roof weight but not much.
I guesstimated 6 props would be best but am being told that's way overkill and they'll get in the way (it's true less would make life easier)?
I guesstimated 6 props would be best but am being told that's way overkill and they'll get in the way (it's true less would make life easier)?
What sort of props are you using?
Roughly how much roof is the load bearing wall supporting?
What sort of floor will the props be bearing onto?
How tall will the props need to be?
ETA: Is the first floor a timber floor? If so, which way are the joists spanning?
Roughly how much roof is the load bearing wall supporting?
What sort of floor will the props be bearing onto?
How tall will the props need to be?
ETA: Is the first floor a timber floor? If so, which way are the joists spanning?
Edited by cv01jw on Tuesday 7th April 11:40
What sort of props are you using? - "Acro's" or "Steel Props" is all I know them as LOL
Roughly how much roof is the load bearing wall supporting? very little I'd imagine, the original cut timbers still bear onto the top of the wall above the bit that's coming out but the roof has been extended up and out past this on lay boards attached to the original ridge, plus the roof was skillin and tiny in the first place so above the wall in question I can't see it being much really?!
What sort of floor will the props be bearing onto? below is a solid concrete on soil floor
How tall will the props need to be? 2.5m
ETA: Is the first floor a timber floor? If so, which way are the joists spanning? yes it is, joists are perpendicular to the wall being removed - I was going to put a lump of 95x250 I've got across the top of the props to spread the support across all joist ends?
Roughly how much roof is the load bearing wall supporting? very little I'd imagine, the original cut timbers still bear onto the top of the wall above the bit that's coming out but the roof has been extended up and out past this on lay boards attached to the original ridge, plus the roof was skillin and tiny in the first place so above the wall in question I can't see it being much really?!
What sort of floor will the props be bearing onto? below is a solid concrete on soil floor
How tall will the props need to be? 2.5m
ETA: Is the first floor a timber floor? If so, which way are the joists spanning? yes it is, joists are perpendicular to the wall being removed - I was going to put a lump of 95x250 I've got across the top of the props to spread the support across all joist ends?
Right. Being my normal (very) conservative self I have assumed some numbers, let me know if any of them are way off (either over or under):
Loads:
- Single skin brickwork wall 3.2m wide x 3m high @ 22kN/m³ = 26.5kN
- First floor load 3.2m x 4m (2m either side) @ 1.5kN/m² = 19kN
- Roof load of 3.2m x 3m (assumed only one side of wall) @ 2.5kN/m² = 24 kN
Total Load = 69.5 kN
For a prop height of 2.5m you need size 1 or 2 acrow. Depending on which you use the typical capacity at 2.5m extension lies between 15-30kN, so you would need at worst 69.5/15 = 5 props.
I haven't factored the loads up (which I would normally do if this was done for work) as the Acrow load ratings are already factored down, and I see little point in overfactoring everything.
I would suggest using a spreader board above and below the props to distribute the load - although the floor is concrete a load of 1.5 tonnes on a acrow could easily damage the surface. A top plate will ensure yu pick up enough of the timber joists to stay safe.
Just had a thought: are you planning on using Strongboys with the Acrows? These are relatively low capacity (about 7kN I think) and would require me to rethink the loads a bit less conservatively.
Loads:
- Single skin brickwork wall 3.2m wide x 3m high @ 22kN/m³ = 26.5kN
- First floor load 3.2m x 4m (2m either side) @ 1.5kN/m² = 19kN
- Roof load of 3.2m x 3m (assumed only one side of wall) @ 2.5kN/m² = 24 kN
Total Load = 69.5 kN
For a prop height of 2.5m you need size 1 or 2 acrow. Depending on which you use the typical capacity at 2.5m extension lies between 15-30kN, so you would need at worst 69.5/15 = 5 props.
I haven't factored the loads up (which I would normally do if this was done for work) as the Acrow load ratings are already factored down, and I see little point in overfactoring everything.
I would suggest using a spreader board above and below the props to distribute the load - although the floor is concrete a load of 1.5 tonnes on a acrow could easily damage the surface. A top plate will ensure yu pick up enough of the timber joists to stay safe.
Just had a thought: are you planning on using Strongboys with the Acrows? These are relatively low capacity (about 7kN I think) and would require me to rethink the loads a bit less conservatively.
cv01jw said:
Right. Being my normal (very) conservative self I have assumed some numbers, let me know if any of them are way off (either over or under):
Loads:
- Single skin brickwork wall 3.2m wide x 3m high @ 22kN/m³ = 26.5kN
- First floor load 3.2m x 4m (2m either side) @ 1.5kN/m² = 19kN
- Roof load of 3.2m x 3m (assumed only one side of wall) @ 2.5kN/m² = 24 kN
Total Load = 69.5 kN
For a prop height of 2.5m you need size 1 or 2 acrow. Depending on which you use the typical capacity at 2.5m extension lies between 15-30kN, so you would need at worst 69.5/15 = 5 props.
I haven't factored the loads up (which I would normally do if this was done for work) as the Acrow load ratings are already factored down, and I see little point in overfactoring everything.
I would suggest using a spreader board above and below the props to distribute the load - although the floor is concrete a load of 1.5 tonnes on a acrow could easily damage the surface. A top plate will ensure yu pick up enough of the timber joists to stay safe.
Just had a thought: are you planning on using Strongboys with the Acrows? These are relatively low capacity (about 7kN I think) and would require me to rethink the loads a bit less conservatively.
Lovely job, thank you muchly Loads:
- Single skin brickwork wall 3.2m wide x 3m high @ 22kN/m³ = 26.5kN
- First floor load 3.2m x 4m (2m either side) @ 1.5kN/m² = 19kN
- Roof load of 3.2m x 3m (assumed only one side of wall) @ 2.5kN/m² = 24 kN
Total Load = 69.5 kN
For a prop height of 2.5m you need size 1 or 2 acrow. Depending on which you use the typical capacity at 2.5m extension lies between 15-30kN, so you would need at worst 69.5/15 = 5 props.
I haven't factored the loads up (which I would normally do if this was done for work) as the Acrow load ratings are already factored down, and I see little point in overfactoring everything.
I would suggest using a spreader board above and below the props to distribute the load - although the floor is concrete a load of 1.5 tonnes on a acrow could easily damage the surface. A top plate will ensure yu pick up enough of the timber joists to stay safe.
Just had a thought: are you planning on using Strongboys with the Acrows? These are relatively low capacity (about 7kN I think) and would require me to rethink the loads a bit less conservatively.
I think that all looks reasonable!No, I don't need Strongboys, the wall is coming our right up to joist level and the joists continue over the top of the wall for a good metre, so just a spreader board directly under the joists.
Davi said:
...the wall is coming our right up to joist level and the joists continue over the top of the wall for a good metre, so just a spreader board directly under the joists.
If I understood that correctly, you plan to put the props to one side of the new opening, under the timber joists?If so, would you not need something to support the single skin wall above the one you are removing?
cv01jw said:
Davi said:
...the wall is coming our right up to joist level and the joists continue over the top of the wall for a good metre, so just a spreader board directly under the joists.
If I understood that correctly, you plan to put the props to one side of the new opening, under the timber joists?If so, would you not need something to support the single skin wall above the one you are removing?
5 or six acros will be fine just make sure they are supported well.
So the upstairs wall is sitting on the joists?
Is the steel going to be sitting under the floor joists then? then you will build bettween steel and the block work?? or have i got the wrong end of the stick?
Just a few points you may not have thought about.
Main thing is to turn the radio up.
Make sure you have your steel in place before putting the acros up.
No need to used the 9 x 3 just use some scaffold planks doubled up.
All ways nail the acros to the planks, don't want them fallling.
Remember you will need some acros to support the steel while the padstons are setting.
Leave the acros up for a few days.
Best of all good luck.
HTH
Also if the house falls down don't blame me, as i haven't seen the job, so i'm not liable (sp)
So the upstairs wall is sitting on the joists?
Is the steel going to be sitting under the floor joists then? then you will build bettween steel and the block work?? or have i got the wrong end of the stick?
Just a few points you may not have thought about.
Main thing is to turn the radio up.
Make sure you have your steel in place before putting the acros up.
No need to used the 9 x 3 just use some scaffold planks doubled up.
All ways nail the acros to the planks, don't want them fallling.
Remember you will need some acros to support the steel while the padstons are setting.
Leave the acros up for a few days.
Best of all good luck.
HTH
Also if the house falls down don't blame me, as i haven't seen the job, so i'm not liable (sp)
Autonotiv said:
5 or six acros will be fine just make sure they are supported well.
So the upstairs wall is sitting on the joists?
Is the steel going to be sitting under the floor joists then? then you will build bettween steel and the block work?? or have i got the wrong end of the stick?
Just a few points you may not have thought about.
Main thing is to turn the radio up.
Make sure you have your steel in place before putting the acros up.
No need to used the 9 x 3 just use some scaffold planks doubled up.
All ways nail the acros to the planks, don't want them fallling.
Remember you will need some acros to support the steel while the padstons are setting.
Leave the acros up for a few days.
Best of all good luck.
HTH
Also if the house falls down don't blame me, as i haven't seen the job, so i'm not liable (sp)
LOL if the house falls down I'll blame the bloke that told me 4 would be plenty So the upstairs wall is sitting on the joists?
Is the steel going to be sitting under the floor joists then? then you will build bettween steel and the block work?? or have i got the wrong end of the stick?
Just a few points you may not have thought about.
Main thing is to turn the radio up.
Make sure you have your steel in place before putting the acros up.
No need to used the 9 x 3 just use some scaffold planks doubled up.
All ways nail the acros to the planks, don't want them fallling.
Remember you will need some acros to support the steel while the padstons are setting.
Leave the acros up for a few days.
Best of all good luck.
HTH
Also if the house falls down don't blame me, as i haven't seen the job, so i'm not liable (sp)
The upstairs wall is sitting on and between the joists - the joists were bedded into the wall. The steel is indeed being fitted below the joists to match existing drop ceilings. I'll try to do it with as little disturbance to the infill blocks as possible, but if they come down I'll just re-bed them once I've finished getting the steel in place
(provided they haven't fallen on my head... )Good point on the steel support - hadn't thought of that, will get a few more! Found out the place down the road is doing them at £2 a week so not exactly a bank breaker...
Are you relying on the existing joists to cantilever from the acro prop supports towards the outside wall and support the brickwork?
Edit
If so there could be some quite large shear loads in the joists at the supports, I suppose the other option would be to use needles through the wall with supports either side of the wall. How close are you going to get the line of acros to the wall/steel?
Edit
If so there could be some quite large shear loads in the joists at the supports, I suppose the other option would be to use needles through the wall with supports either side of the wall. How close are you going to get the line of acros to the wall/steel?
Edited by ALawson on Tuesday 7th April 22:51
Hi,
following on the back of this post I have a similar question. We have a 200 year old cottage, originally 2 up 2 down. This has been extended backwards with a two storey extension, on one side, followed by a second single storey extension next to it at a later date. The roof heights of the extensions are both slightly different heights. And both extension roofs are substantially lower than the first floor level of the original house.
We are going to remove a portion of the original back wall and replace with a gateway portal. We have two problems.
1) how do we support the wall above the removal since we can't get needles through it (the roof and first floor of the two extensions are in the way)
2) the floor is a 2.5" concrete slab over packed earth and our builder is a little concerned about the props damaging the floor. I want to suggest that he spread the load using a stable thick board or beam, but want to check first because he's quite likely to dismiss my 'girly' suggestions, it wouldn't be the first time.
The main house is about 8.5m long.
The wall we want to knock out is 3.8m starting at one gable end.
The wall is double skin brick. The floor joists in the first floor of the main house run into this wall, so could possibly be used as support if propped, according to our Steel manufacturer but our builder is not so sure.
The height from ground floor to underneath the first floor joists is 2m 70 approx.
I'm desperate now. The builder's father was our structural engineer. He originally said we had subsidence at one end of the house. That diagnosis meant we had to strip one half of the house back to bare structure so he could assess, so we decided to renovate totally. He then delayed and delayed in actually writing his report and schedule. Six weeks later he said, that there was in fact no subsidence. Our house is uninhabitable and we are despeartely trying to get it sorted now as we have been paying mortage and rent for four months already.
Any help or advice would be hugely appreciated.
following on the back of this post I have a similar question. We have a 200 year old cottage, originally 2 up 2 down. This has been extended backwards with a two storey extension, on one side, followed by a second single storey extension next to it at a later date. The roof heights of the extensions are both slightly different heights. And both extension roofs are substantially lower than the first floor level of the original house.
We are going to remove a portion of the original back wall and replace with a gateway portal. We have two problems.
1) how do we support the wall above the removal since we can't get needles through it (the roof and first floor of the two extensions are in the way)
2) the floor is a 2.5" concrete slab over packed earth and our builder is a little concerned about the props damaging the floor. I want to suggest that he spread the load using a stable thick board or beam, but want to check first because he's quite likely to dismiss my 'girly' suggestions, it wouldn't be the first time.
The main house is about 8.5m long.
The wall we want to knock out is 3.8m starting at one gable end.
The wall is double skin brick. The floor joists in the first floor of the main house run into this wall, so could possibly be used as support if propped, according to our Steel manufacturer but our builder is not so sure.
The height from ground floor to underneath the first floor joists is 2m 70 approx.
I'm desperate now. The builder's father was our structural engineer. He originally said we had subsidence at one end of the house. That diagnosis meant we had to strip one half of the house back to bare structure so he could assess, so we decided to renovate totally. He then delayed and delayed in actually writing his report and schedule. Six weeks later he said, that there was in fact no subsidence. Our house is uninhabitable and we are despeartely trying to get it sorted now as we have been paying mortage and rent for four months already.
Any help or advice would be hugely appreciated.
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