Spacing/supporting mesh in Slab

[SuperJohnG]

I've an insulated foundation from Kore due to kick off shortly and working out all the details. 

 

Hit a little stumbling block on how to support some of the mesh. 

 

I have a 250mm deep ringbeam with 150mm thickness on the rest of slab. Tanners provided the mesh type and detail etc, but I am trying to figure out the best route for supporting the mesh. 

 

The lower A393 can be on mesh castles at 40/50mm as required - I was even thinking on doing 'mars bars' (actual name!) as that seemed even quicker.

 

The inner A252mesh, should be easy enough also with 75mm castles or mars bars again. However I am struggling find much info on how to support that upper section of A393 mesh. I done a CAD drawing below and added some some sizes. I assume the actual spacings are not set in stone (pun not intended) as long as you have the steel in there?

 

75mm down from the top of the slab seemed to make sense to me, hence I have 125mm gap to fill, how is it best to do this? Are Hy chairs what should be used here?

 

 

 

 

 

any steer appreciated. I may be overthinking it - I'm a Mechanical engineer and this building malarkey all seems a bit loose for me.. 

[Alexphd1]

One solution is get some rebar bent into a u shape and tie it the lower a393 mesh below.

[PeterW]

Can you not run 125mm triangular deck chairs

to support the upper layers ..?

 

https://tzursteel.co.uk/products/continuous-wire-chair-2m-lengths-each-spacer-from-50mm-to?variant=27962143604759&gclid=EAIaIQobChMIwueI17Sr7QIVqujtCh1EYw10EAQYASABEgKk5PD_BwE

[Alexphd1]

This is what I was meaning, we had more rebar in our spec. I think the triangle deck chairs is a easier solution. 

[Russell griffiths]

As peter said, steel supplier does a mesh support that is shaped like a z, you can squish them down a bit if needed. 

 

I would also use mars bars wherever you can as the plastic spacers crush if stood on by a fat concreter. 

Edited December 1, 2020 by Russell griffiths

[LA3222]

John,

 

I used plastic mesh spacers under the bottom sheets - did look at mars bars but for the qty required they seemed expensive. In the thickened areas where two sheets are stacked I used mesh hystools and tied them to the top and bottom mesh sheets.

 

 

 

 

[SuperJohnG]

9 hours ago, PeterW said:

Can you not run 125mm triangular deck chairs

to support the upper layers ..?

 

https://tzursteel.co.uk/products/continuous-wire-chair-2m-lengths-each-spacer-from-50mm-to?variant=27962143604759&gclid=EAIaIQobChMIwueI17Sr7QIVqujtCh1EYw10EAQYASABEgKk5PD_BwE

Thanks - yep that was the things I was thinking. 

 

1 hour ago, Russell griffiths said:

As peter said, steel supplier does a mesh support that is shaped like a z, you can squish them down a bit if needed. 

 

I would also use mars bars wherever you can as the plastic spacers crush if stood on by a fat concreter. 

Mars bars seemed to make sense as then you can just sit them on the EPS and then put the steel on top quickly. It'll be post xmas for me now, so no doubt the extra support will maybe required for me, ?

 

23 minutes ago, LA3222 said:

John,

 

I used plastic mesh spacers under the bottom sheets - did look at mars bars but for the qty required they seemed expensive. In the thickened areas where two sheets are stacked I used mesh hystools and tied them to the top and bottom mesh sheets.

 

 

Thanks @LA3222 I was scouring the pics in your thread last night on the mesh castles, but I couldn't see them in there. Any advice on spacing of them? I think I will go simialr route to you, so it's all very solid to walk on. I assume the hystools are just the same as the items Peter mentioned above? 

[LA3222]

Yeah the hystools are triangular and available in loads of heights. They are 2m long iirc. I tended to stagger them, much like how you plant a double row hedge, but then I pulled them in slightly so all the ends overlapped by about 150mm - I was looking this morning but couldn't find any pics which clearly show it.

 

Check your height before you order. I cocked up and ordered wrong size. I sized it off the gap between sheets, didn't think about how when A393 bars cross each other the sheet is actually 24mm thick, not 12mm thick. 

[LA3222]

When I tied them to the sheets I just did 4 or 5 on bottom legs and then same to top, like a zig zag.

[SuperJohnG]

 

5 hours ago, LA3222 said:

Check your height before you order. I cocked up and ordered wrong size. I sized it off the gap between sheets, didn't think about how when A393 bars cross each other the sheet is actually 24mm thick, not 12mm thick. 

Great wee bit of info. 

 

5 hours ago, LA3222 said:

When I tied them to the sheets I just did 4 or 5 on bottom legs and then same to top, like a zig zag.

And this too - cheers

 

Think I should have enough info to figure this part out now. 

 

Unfortunately looks like January for doing this for me - I know I shouldn't but hey ho - I need to get going!  

[LA3222]

1 hour ago, SuperJohnG said:

Unfortunately looks like January for doing this for me - I know I shouldn't but hey ho - I need to get going!  

Snap. I did mine in January/Feb this year and poured the concrete towards end of march.

 

The weather was honking, it was storm after storm. I was lucky and it stayed dry during the groundworks part, it was when I started to install the DPM and the mesh that the weather turned crap.  Bad times, but like anything they soon become a distant memory.  Hopefully you'll have better luck with the weather.

 

Did you get anywhere with your padstones under the slab? 

[SuperJohnG]

5 hours ago, LA3222 said:

Snap. I did mine in January/Feb this year and poured the concrete towards end of march.

 

The weather was honking, it was storm after storm. I was lucky and it stayed dry during the groundworks part, it was when I started to install the DPM and the mesh that the weather turned crap.  Bad times, but like anything they soon become a distant memory.  Hopefully you'll have better luck with the weather.

 

Did you get anywhere with your padstones under the slab? 

???

 

Pad stones all gone under the slab fortunately. We deepened the ringbeam to 250mm and now 150mm the rest of the slab, which removed them. I still have 5 external to the slab as I have a very large canopy (3m) over the glazed gable, but they are straightforward as it's just on soil and no need to cut through EPS and position blocks.  I'm not sure I'll specifically have saved money there as is extra concrete obviously, but when i done the volume calc it was 31m^3 and I had originally budgeted for 36 so I coudl have probably saved some more money but I would have lost it in days explaining to the groundworkers that will help with labour or paying them to stand and watch me cut through EPS. It's simpler so I'm happy there. 

 

Hoping the weather holds up in January, only thing concerning me is the rain causing hassle as I am west coast.  Interestingly, no DPM required inside my formwork, just underneath then wrapped up the edges of the outside. I think the difference being here is that I don't have a brick/block outer layer.  Just render board, which again helps simplify. 

 

I was very pleasantly surprised with my quote from Kore today which has come out at less than originally estimated despite becoming 100mm deeper on the edge profiles and an extra layer of EPS. 

[LA3222]

Good to hear its working out for you bud. I never even thought to ask about thickening the slab to do away with the padstones, 100% thats the best way forward. Makes it far easier for you. Likewise your dpm under the EPS will help make it easier. Your kore quote came in cheaper too - that's three good things there?

[SuperJohnG]

Yeah I'm pleased so far, a lot of it is just understanding what's required and being part of the forum and getting insight from others,  like yourself, helps massively.