Concrete Cover

[LA3222]

The concrete cover as specified on foundation drawings, is this a minimum or what is must be? My drawings state 30-40mm cover, does that mean the mesh needs to sit in that zone from the top of the concrete or is this a minimum figure, so the steel can sit at 50mm below the finished surface? 30-40mm don't leave a lot in areas that lap as the top sheet in the lap is pushed higher and when I attach UFH pipes there won't be much cover there at all.

[Russell griffiths]

Minimum cover to protect steel from corrosion, and to allow correct strength to be achieved. 

It can sit lower, but then you don’t want it to close to the underside, how thick is your slab. 

100mm???

[LA3222]

12 minutes ago, Russell griffiths said:

Minimum cover to protect steel from corrosion, and to allow correct strength to be achieved. 

It can sit lower, but then you don’t want it to close to the underside, how thick is your slab. 

100mm???

Yarp, 100mm in the thin part, 200mm in the perimeter.  I've got a load of 40/50meshmen which I have used at the 50mm height but I'm not happy with the cover on overlaps so am thinking to spin them all around to the 40 as this will put the steel roughly in the middle of the 100mm around areas and give me about 30mm (top of steel to top of concrete) of cover over the parts which overlap where its about 25mm at the minute.

Edited March 8, 2020 by LA3222

[Russell griffiths]

That’s it. Make sure you tie the laps well, in case they pop up as somebody stands in the middle. 

[scottishjohn]

or use fibre addition to slab concrete --no need for steel then ?

sure i will be corrected if wrong