Floor make up

[LSB]

I'm confused, not for the first or last time I know.

 

But, just doing quotes for our floor makeup and looking at the SE & BC drawings, same thing really.

 

Anyway, they's specified B705 mesh, neither BC nor BM have not heard of this.

I went back to the architect and he said, that's was SE specified, SE not available.

 

As it is I think this floor makeup is excessive for a single storey building, but BC is saying that we must follow the drawings.

 

What do others think.

 

 

The screed is only speced at 50, the hard core (not listed) at 200 and the insulation at 150, ignore the bit at the top, that's the existing floor that we have had to dig out to provide more roof height.

The nearest spec to B705 is B785, which is £83 per sheet compared with £30 for A rated mesh.

 

thoughts please.

 

 

Edited October 2, 2023 by LSB

[JohnMo]

With the cellcore, the architect is expecting some ground movement below the slab. Could be the B705 is a typo.

 

Can you not miss out the architect and go direct to the SE?

[LSB]

  On 02/10/2023 at 12:00, JohnMo said:

With the cellcore, the architect is expecting some ground movement below the slab. Could be the B705 is a typo.

 

Can you not miss out the architect and go direct to the SE?

Expand  

We are converting an old barn, one corner is clay (about 9sqm out of 240), hence the cellcore, but that  is also included on the rest which is sand, hey ho.

I have gone to the SE, but they haven't come back to me, just rang again and was told no one was available.  We had the plans drawn back in Nov 2020 so I think maybe they are not interested any more, the receptionist couldn't find our plans.

I wondered about a typo, but B705 is everywhere in all the calcs. when copy and paste doesn't ring true.

Pity the architect didn't notice when he did the BC drawings, from the SE drawings.

BC said that there has never been a B705 so it's not like Persil, the new improved version.

 

What with the cellcore and high spec mesh (2 layers) the floors are going to be very expensive.

 

 

 

[Alan Ambrose]

>>> but B705 is everywhere in all the calcs

 

Maybe there's another detail clue somewhere there on the drawings? Weight / wire size / sheet size etc? It's presumably B785 - sounds like an easy typo for someone doing CAD from the SE's hand drawn notes?

[LSB]

  On 02/10/2023 at 13:21, Alan Ambrose said:

>>> but B705 is everywhere in all the calcs

 

Maybe there's another detail clue somewhere there on the drawings? Weight / wire size / sheet size etc? It's presumably B785 - sounds like an easy typo for someone doing CAD from the SE's hand drawn notes?

Expand  

I expect so, waiting on a call back from SE although they didn't' respond to my email

I'll chase tomorrow otherwise

 

Shows that even though it is written by A and checked off by B they both maybe missed it.

Just frustrating as I wanted to get prices today and I can't really guarantee that I'm looking for the right thing.

That's the trouble with working and acting as PM, limited time availability during office hours.

 

 

[Mr Punter]

It is probably B785.  Never used it myself.  The B meshes have different gauges and spacing of wires, so I imagine they should be placed in the correct orientation?

 

It will be heavy and awkward to handle.

[kandgmitchell]

B785 has 10mm bars 100mm apart and 8mm cross bars 200mm apart, so it looks like the SE expected the slab to span further in one direction than the other. I wouldn't swap it for an A mesh which has the same bar thickness set equidistant in both directions without checking with the SE first (albeit proving hard to do). 

[LSB]

  On 03/10/2023 at 08:59, kandgmitchell said:

B785 has 10mm bars 100mm apart and 8mm cross bars 200mm apart, so it looks like the SE expected the slab to span further in one direction than the other. I wouldn't swap it for an A mesh which has the same bar thickness set equidistant in both directions without checking with the SE first (albeit proving hard to do). 

Expand  

yep, just rang them again !!!!

in a meeting and will call me back, just like the last 3 times I rang.

Architect says that they just used what SE said.

I don't plan to swop for A mesh, it's just the BC says that we must do as per the SE spec, which doesn't exist.

 

The hardcore is being put in today and then I'm stuck until I can get this stuff.

 

 

[LSB]

At last the SE rang back and admitted that it is B785, so a typo all though the document and double checked by a senior.

I also questioned having 2 layers of B785 for a single storey residential floor that will only have household furniture on top.

He's now checking if that is really necessary.

 

Shows how much we've learnt since we go the drawings 2 years ago when we just took what they said as gospel.

 

[George]

Don't see B-meshes out in the wild very often. #

 

As it's a suspended slab it probably does need fairly heavy-ish reinforcement.

 

You could replicate the B785 spec with A393 with additional loose 10mm bars every 200mm (so slot between the A393 squares). This would be easier to get hold of.

 

However do make them check because a 200mm thick slab with 10mm main reinforcement is pretty hefty for domestic purposes. Not mad or necessarily over the top... but... hefty.

 

 

 

Engineers are human and usually working to tight deadlines and low fees. Pity them and never trust them/us blindly. 

Edited October 3, 2023 by George

[LSB]

  On 03/10/2023 at 11:42, George said:

Don't see B-meshes out in the wild very often. #

 

As it's a suspended slab it probably does need fairly heavy-ish reinforcement.

 

You could replicate the B785 spec with A393 with additional loose 10mm bars every 200mm (so slot between the A393 squares). This would be easier to get hold of.

 

However do make them check because a 200mm thick slab with 10mm main reinforcement is pretty hefty for domestic purposes. Not mad or necessarily over the top... but... hefty.

 

 

 

Engineers are human and usually working to tight deadlines and low fees. Pity them and never trust them/us blindly. 

Expand  

I spoke to SE today and he has reduced half the site to A mesh but is adamant that the bit we are doing must be B785

I can't replicate anything as BC is insisting that we follow the drawings exactly.

Luckily i can get it from Jewsons, but lots of places don't provide it, and it's expensive.

 

Apparently it's to do with the roof, this part of the barn has it's own roof and is 6*4 sqm approx. internally.

Our SE is a commercial company more used to doing hospitals so guess to them it's a minimal spec.

 

[Russell griffiths]

Why are you sourcing mesh from a builders merchants. 

Go straight to a steel mesh supplier. 

Total construction supplies in the west maids did mine, 40% cheaper than a merchants. 

[LSB]

  On 03/10/2023 at 14:26, Russell griffiths said:

Why are you sourcing mesh from a builders merchants. 

Go straight to a steel mesh supplier. 

Total construction supplies in the west maids did mine, 40% cheaper than a merchants. 

Expand  

I've been looking around, delivery is the issue

 

[LSB]

So, got some prices back, Jewson is the cheapest and includes delivery, whereas the suppliers charge extra.

We can also call off when we need.

 

I will try the one you used, thanks for that

[BotusBuild]

I used Hy-Ten at Newton Abbot. In 2021 A393 was 59.21 a sheet ex. VAT

[George]

  On 03/10/2023 at 12:04, LSB said:

I spoke to SE today and he has reduced half the site to A mesh but is adamant that the bit we are doing must be B785

I can't replicate anything as BC is insisting that we follow the drawings exactly.

Luckily i can get it from Jewsons, but lots of places don't provide it, and it's expensive.

 

Apparently it's to do with the roof, this part of the barn has it's own roof and is 6*4 sqm approx. internally.

Our SE is a commercial company more used to doing hospitals so guess to them it's a minimal spec.

 

Expand  

Did you ask them if the A393 mesh + 10mm loose bars @200mm centres is an acceptable alternative to the B785 mesh?

 

 

Difference in cost may not be massive but lead times could be better. 

 

 

Edited October 3, 2023 by George

[LSB]

  On 03/10/2023 at 15:46, George said:

Did you ask them if the A393 mesh + 10mm loose bars @200mm centres is an acceptable alternative to the B785 mesh?

 

 

Difference in cost may not be massive but lead times could be better. 

 

 

Expand  

yes, They have agreed to A393 for part of the build (we are building in sections), but the part we are doing must be B785, he did tell me why, but the digger was going at the time and i didn't fully hear him, something to do with the roof.

He is going to followup with an email.

 

[LSB]

  On 03/10/2023 at 14:26, Russell griffiths said:

Why are you sourcing mesh from a builders merchants. 

Go straight to a steel mesh supplier. 

Total construction supplies in the west maids did mine, 40% cheaper than a merchants. 

Expand  

again more expensive for me than Jewsons 🙂

I don't even much like Jewson's but their initial price has not yet been beaten, not that I'm going to tell them that.

 

[George]

  On 03/10/2023 at 16:06, LSB said:

yes, They have agreed to A393 for part of the build (we are building in sections), but the part we are doing must be B785, he did tell me why, but the digger was going at the time and i didn't fully hear him, something to do with the roof.

He is going to followup with an email.

 

Expand  

Yeah it'd need the 10mm bars as well, not just a swap to A393.

[Russell griffiths]

  On 03/10/2023 at 17:44, George said:

Yeah it'd need the 10mm bars as well, not just a swap to A393.

Expand  

Why would it need the A393, why not just tie it up in 10mm bar. 

How does the cost of loose bar compare to sheet ??

is it still just based on per tonne price or is sheet a premium price?? 

[saveasteading]

Sheet costs a bit more because of transporting air, but tying loose bar is a real skill, so I suggest stick with the nesh.

[LSB]

  On 03/10/2023 at 18:06, Russell griffiths said:

Why would it need the A393, why not just tie it up in 10mm bar. 

How does the cost of loose bar compare to sheet ??

is it still just based on per tonne price or is sheet a premium price?? 

Expand  

I don't know Russell, I'm just using the SE instructions as that is what the BC is using.  SE have re-checked the specs and confirmed what we must use so it's not down to me to try and do something else.

It took us a long time to get planning and to get going so we are now just cracking on unless something is obviously wrong.

 

 

[saveasteading]

Mesh is sensible, spanning the shorter dimension. How far does it span?

[ETC]

  On 03/10/2023 at 15:46, George said:

Did you ask them if the A393 mesh + 10mm loose bars @200mm centres is an acceptable alternative to the B785 mesh?

 

 

Difference in cost may not be massive but lead times could be better. 

 

 

Expand  

…………….Or two layers of A393 on top of each other with the mesh staggered at 100mm centres?

[Iceverge]

Unrelated to this but 100mm insulation looks a bit slim. Can you boost it at all?