Padstone specification

[Steven Spalding]

Hi, new on here and hoping for some advice. I’m taking down an internal (was originally external) wall to make a decent sized kitchen dining room. The previous owners had built a sun porch extension with polycarbonate roof behind the kitchen, which I’m replacing with a warm deck flat roof. I’ve got the building warrant and planning permission. I’ve since taken down the section of wall and next I’m fitting the padstone. My plans specify the UBs sit on a 200x150x215 deep padstone and cast in 150 concrete surround UNO.
The total width of the cavity wall is 280mm so shouldn’t the padstone span across more of the thickness of the wall i.e should I be get a thicker one than specified above and do I also need to key in bricks all the way up at the open ends to retain strength. I’m happy to go back to my SE and question this, but they really slow at responding so wanted your opinion if it’s even something I should question with them. I’ve attached a photo and plans to help visualise my ramblings!!

 

[23vc]

You can make the padstone bigger, not sure why it’s not just the full wall width either. Maybe a minimum has been specified, but common sense/ease of installation would mean using the full width.

 

[Steven Spalding]

Thanks that makes sense to me as well.

 

[^woody^]

If you have a cavity wall, then you don't need a padstone wider than the wall leaf as you can't bear on to fresh air.

You don't need to rebuild the jamb to close and bond the cavity, unless the SE specifically instructs this in his loading calculations - normally not needed.

 

[Steven Spalding]

If you have a cavity wall, then you don't need a padstone wider than the wall leaf as you can't bear on to fresh air

Thanks Woody, so if I understand correctly the padstone shouldn’t be wider than the leaf which is a 4in brick. So I should go back to my SE and get a specification that works for my leaf thickness

 

[^woody^]

Sorry, I can see the photos now, and it looks like the beam is central to the cavity and the padstone is spanning across the cavity but is not as wide as the wall - which is confusing and non standard, and then there is this concrete surround - which I can't see the purpose of.

So yes your original question about the padstone should be spanning the whole wall is valid.

I can't see why you can't use a bigger padstone to span the wall width and to the same length and height as otherwise specified.

But that still leaves this concrete surround, and you need to ask the engineer about that.

 

[Steven Spalding]

But that still leaves this concrete surround, and you need to ask the engineer about that.

Thanks, I went back to the SE today and they have changed the padstone specification to a 100x215x400 sitting directly on top of the inner leaf. Glad I queried it now!
Also on the concrete surround it just means incase the UB once in place to help stop any movement. I can ignore the 150.

Thanks again for your replies.

 

[^woody^]

sitting directly on top of the inner leaf. G

That's odd, as the drawings show the beam sitting centrally to the wall.

Engineers ?

 

[Steven Spalding]

That's odd, as the drawings show the beam sitting centrally to the wall.

Engineers ?

Got the updated drawings in the post today, so everything is in order. Just as well as I'd cemented in the padstones last week

Thanks again for your help on this.

 

[Steven Spalding]

Update: Got the Beams and post installed. (took most of yesterday wrangling them into place with a genie). Once I tightened everything up, the beam that connects to the post and fin plate isn't centred on the opposite padstone (that's me to blame for being out with where I installed the post). I spoke to the Steel fabricator who thought it would be fine and also my architect, who was pesimistic. I'm waiting for my SE to respond. Obviously being centred would be my 1st choice, but after 8 hours of getting them in place the 1st time, I'm only going to do this if really required, my ocd will just have to live with it. But I wondered if there was any official guideline on this. Is it a 100% no-no, will the house fall over when I take the acro props down?

 

[^woody^]

It looks a bit too much, but you never know

 

[garyo]

That first photo looks like it's as much the padstone being out as the beam. If so, can you just correct the padstone and it may be acceptable then.

 

[Steven Spalding]

That first photo looks like it's as much the padstone being out as the beam. If so, can you just correct the padstone and it may be acceptable then.

Yeah I agree it could come over a few mm. Looking at it again last night, i could change the side that the web of the beam sits against the fin plate which would give me 10mm at least, just means the beam would be off center on the post which I don't think would make any difference to the strength / loading. Will go and have my porridge in preparation...

 

[Steven Spalding]

I guess there's no subsitute for experience, my mate helped me move it into place in 30 mins with minimal fuss.