Suitable concrete spec for 40mm floor

Wailin

Steel shed arriving today and will then be laying 40mm of concrete over the concrete base that the shed will be bolted to. For that depth of concrete what would be the most suitable gauge to get a nice smooth finish and no coarseness. Was told to go with 30N10 concrete which I used on the base, what do you guys think? Obviously a layer of DPC will be put down first.

jack of all

If the screed is not to be mechanically bonded to the concrete base then I think 40mm will be too thin and is liable to crack or lift in time. Others may advise better but I think a minimum floating screed thickness of 75mm would be more appropriate on a DPM. A floating screed relies on its own weight to form a solid, durable floor finish that wont lift or delaminate. I say this based on my experience of where a thin screed was used to resurface an old slab, even after careful prep and a primer coat the screed lifted in spots and eventually cracked everywhere, getting progressivelt worse as time went on.

Wailin

jack of all wrote: »

If the screed is not to be mechanically bonded to the concrete base then I think 40mm will be too thin and is liable to crack or lift in time. Others may advise better but I think a minimum floating screed thickness of 75mm would be more appropriate on a DPM. A floating screed relies on its own weight to form a solid, durable floor finish that wont lift or delaminate. I say this based on my experience of where a thin screed was used to resurface an old slab, even after careful prep and a primer coat the screed lifted in spots and eventually cracked everywhere, getting progressivelt worse as time went on.

Yeah I am a bit worried that 40mm is too thin but problem is I have no choice due to the frame of the steel shed. I definitely need to put DPC down to prevent dampness rising so bonding to the concrete slab is not possible. Any other options? Using higher strength concrete maybe?

jack of all

Could you run with a ply floor on treated battens on DPM (still coming close to 50- 60mm overall) but might work better around your steel frame if that's what's worrying you. If you intend using the shed to work in timber is a lot nicer underfoot, kinder to tools if you drop them and you can finish the top with a good expoxy floor paint. If determined to go with concrete there may be a "liquid" DPM available that could be rolled on that may give a mechanical bond to the screed, but I'm only guessing and if possible you can be sure it won't be cheap either and some care will be required.

Wailin

jack of all wrote: »

Could you run with a ply floor on treated battens on DPM (still coming close to 50- 60mm overall) but might work better around your steel frame if that's what's worrying you. If you intend using the shed to work in timber is a lot nicer underfoot, kinder to tools if you drop them and you can finish the top with a good expoxy floor paint. If determined to go with concrete there may be a "liquid" DPM available that could be rolled on that may give a mechanical bond to the screed, but I'm only guessing and if possible you can be sure it won't be cheap either and some care will be required.

Thanks for the advice. There will be some heavy equipment in the shed plus gym equipment so I don't think the wooden floor would be suitable. I think I will just have to take my chances with the readymix. Actually, according to Steeltech website, laying the concrete to 40mm is recommended. Hopefully it will do the job.

wayguk

how did the result work out for you? I am in the same position today and looking for advice

Calahonda52

wayguk wrote: »

how did the result work out for you? I am in the same position today and looking for advice

4 year old thread!
What is your position?
Show has moved on with these sheds so what is you specific set of questions

wayguk

4 year old thread indeed... there's nothing wrong with time is there?! ;-)
My situation is the same... I'm looking to pour a shed floor on top of DPC, however I have concerns about 40mm liable to cracking etc. Should I use a wire mesh to strength? or go with 80mm depth? or use another screed mix??

Lumen

wayguk wrote: »

My situation is the same... I'm looking to pour a shed floor on top of DPC, however I have concerns about 40mm liable to cracking etc. Should I use a wire mesh to strength? or go with 80mm depth? or use another screed mix??

Screed or concrete? And why?

Wailin

wayguk wrote: »

4 year old thread indeed... there's nothing wrong with time is there?! ;-)
My situation is the same... I'm looking to pour a shed floor on top of DPC, however I have concerns about 40mm liable to cracking etc. Should I use a wire mesh to strength? or go with 80mm depth? or use another screed mix??

I have had no issues at all with the 40mm. Bear in mind that its only about a foot around the inside of the shed that has 40mm. Middle has about 100 mm and thats where most of the traffic is so to speak. But I think 40mm all round would still be ok once its good concrete. I have a gym in my shed and weights and barbells get dumped around...no problems at all. Its more important to prevent dampness in these sheds so DPC is essential. I have had no dampness whatsoever in the 4 yrs. Good luck!