Floor Slab - Mesh Required?

[suttonsteve]

Hello All - 1st post - here goes

New extension to rear of the house, approx 8m x 5m. I am ready to have floor slab concrete poured onto DPM. Neither my drawings nor Building Control have requested reinforcing mesh be put into the concrete. Does this sound Ok - I am concerned about cracking later.
The construction is 150mm Hardcore with 50mm sand blinding and the DPM, 100mm concrete and then vapour layer, insulation and screed (with UFH) to go on top of slab.
Thanks in advance

 

[garyo]

Hi Steve,

I met with my BCO this morning. Despite not requiring mesh on the plans that he's signed off, he's now asked me to include some A142.

My external dims are 3.5M x 4.6M. 100mm slab, with 100mm PIR insulation under and around slab (i.e. fully floating, so I can see why cracking could be more of an issue than with yours)

Gary

 

[theoldun]

Steve, Not quite right.
The way we go is, sub ground, 100mm min, 500mm max sub grade, 12mm sand blinding, 1200g poly, celotx insulation, you should then have 500g VB, but we never bother, just tape the joints, UFH in 75mm min screed.
No mesh or RB required..
Regards oldun

 

[garyo]

Nice to see you around again oldun!

Interesting idea with the joint taping - that'll save me a few quid and a load of hassle.

Gary

 

[theoldun]

Gary, Lot of BC now asking for mesh in oversite when insulation is laid under slab.
We never lay insulation under slab especially with UFH, although a lot depends on your life style, whether you are at home all day or at work most days.
By the by you could have achieved 0.22W/m2k with 75mm of Celotex GA4000.
Feel good Gary, just hope it lasts.
Regards oldun

 

[theoldun]

Forgot to mention.
Add fibres to your concrete mix to reduce cracking and crazing.
oldun

 

[suttonsteve]

Thanks both for your response

Gary - I see your point, my slab is contained within the inner leaf blockwork and bears onto the hardcore, so presumably less liklehood of movement and cracking

Oldun - my mistake, drawing does show VB on top of insulation then screed.
It is re-assuring that you agree that mesh is not required.

I have another query on the pouring of the concrete but will start a new topic

Thanks again

 

[Norcon]

I have another query on the pouring of the concrete but will start a new topic

We poured 70 ton of the stuff into peri shuttering today inside two hours. Another 80 ton tomorrow. What do you need to know?

 

[theoldun]

QUOTE "Norcon";

We poured 70 ton of the stuff into peri shuttering today inside two hours. Another 80 ton tomorrow. What do you need to know?

Was it 70 ton of bullsh*t stuff
Regards oldun

 

[Norcon]

Was it 70 ton of bullsh*t stuff

No its the real thing. Complete with a resonable price tag too.