Author Topic: Concrete floor inside a shed  (Read 541 times)

Concrete floor inside a shed
« on: 01 October, 2021, 01:35:54 pm »
We have a large barn/shed that will partly become a pottery (well it is already, but with lots of whinging from the potter).

Main problem is the floor. It is rough concrete (previously a barn for animals, so roughed to give grip for hooves). In places it is thin, almost a hole through it, and damp comes up.

My plan was to lay DPM, then pour 10cm of concrete.

I know that the gold standard is to dig-out to firm ground then fill with hardcore, then pour.

Time and cost dictate against doing that. There would be tons of crap to remove. To potter doesn't want extended downtime.

Given that:
A) ground around my house is very solid - digging is difficult, you git rock and boulders just 6" down.
B) The existing crappy concrete hasn't cracked.

Is it daft to just lay 10cm of concrete, using fibre-filled concrete?
<i>Marmite slave</i>

LittleWheelsandBig

  • Whimsy Rider
Re: Concrete floor inside a shed
« Reply #1 on: 01 October, 2021, 01:49:28 pm »
Assuming you are talking macro-fibres or steel fibres, rather than just micro-fibres, I think pouring over the top would probably work. Macro-fibres will create a ‘hairy surface’ that you would probably need to burn or trim off.

Will your DPM be taped sheeting, sprayed membrane or something else?
Wheel meet again, don't know where, don't know when...

Re: Concrete floor inside a shed
« Reply #2 on: 01 October, 2021, 02:14:13 pm »
Assuming you are talking macro-fibres or steel fibres, rather than just micro-fibres, I think pouring over the top would probably work. Macro-fibres will create a ‘hairy surface’ that you would probably need to burn or trim off.

Will your DPM be taped sheeting, sprayed membrane or something else?

Sheeting - I will be able to do it with one sheet, no taping.

I'm intending to use 4x2 around the sides to give me something to scree off to for a level. These would remain in place to give me something for the stud walling to screw down on.

I could put 4x2 down the middle for screeding, then pull that out when most of the floor is down.

It was this job that a local firm quoted £3 900 to do. The concrete will be £1000.
<i>Marmite slave</i>

Re: Concrete floor inside a shed
« Reply #3 on: 01 October, 2021, 02:33:19 pm »
Only comment I’d make is I don’t think you need 2” thick for a screeding guide. But hey, if you’ve got all the 4x2’s then why not. As to surface, a self levelling compound of some sort?
We are making a New World (Paul Nash, 1918)

Re: Concrete floor inside a shed
« Reply #4 on: 01 October, 2021, 03:14:09 pm »
Only comment I’d make is I don’t think you need 2” thick for a screeding guide. But hey, if you’ve got all the 4x2’s then why not. As to surface, a self levelling compound of some sort?

That is a very good point - I think I'll get some lighter-weight timber for some of the guides.

Timber is £££ now. £20 for 4.8m of 4x2
<i>Marmite slave</i>

Re: Concrete floor inside a shed
« Reply #5 on: 01 October, 2021, 03:26:09 pm »
You could polish the concrete or use a decent garage floor paint.
Get a bicycle. You will never regret it, if you live- Mark Twain

Re: Concrete floor inside a shed
« Reply #6 on: 01 October, 2021, 03:30:36 pm »
Worth sticking any insulation in there?

LittleWheelsandBig

  • Whimsy Rider
Re: Concrete floor inside a shed
« Reply #7 on: 01 October, 2021, 03:39:57 pm »
I assume the existing concrete’s surface texture will provide sufficient interlock between the new and old concrete, despite the DPM bondbreaker that you are installing.
Wheel meet again, don't know where, don't know when...

Re: Concrete floor inside a shed
« Reply #8 on: 01 October, 2021, 03:48:19 pm »
Instead of a screed layer over the new concrete you could use the interlocking pvc garage floor tiles providing that the surface of the new concrete is reasonably flat/level.  They make a good surface to walk on and are quick and easy to install.  They are not particularly cheap but once you have factored in the cost of a screed layer might not be so bad, and the surface is a lot better than plain screed or painted screed.

Re: Concrete floor inside a shed
« Reply #9 on: 01 October, 2021, 05:04:32 pm »
The existing surface is too uneven to just lay tiles, and because the use is for a pottery, it must be a surface than can be wet mopped (smooth and sealed).

The existing surface is pretty rough so I don't think there will be a problem with interlocking. It is also constrained by the (very substantial) walls.

I'm thinking of garage floor paint as a finish, yes.
<i>Marmite slave</i>

Re: Concrete floor inside a shed
« Reply #10 on: 02 October, 2021, 07:33:25 am »
Many of the self-leveling products are rather wet (in order to be flowable).  For more durable concrete, you either need to get a "really good" (and more expensive) self-leveling material, or try for a drier mix for the concrete.  When the water dries out, the concrete tends to crack.  I would suggest scoring the surface at about 10-12', 3-4 m, on center, each way.  That will encourage the cracks to find the score joints.  Those joints can be filled with sealant if you want a smooth surface.

The garage floor paint will probably say "allow concrete to cure for 28 days" (or more) on the label.  That to try to give the concrete some time to dry.  That waiting time might impact the potter's ability to get back to work.

Any lumber that is embedded in the concrete should be preservative treated, to slow its rotting.  Wood that is treated for "ground contact" will have more of the preservative chemicals.

"Hairy concrete" was a problem several decades ago when the fiber reinforcing products were first introduced.  Most cement finishers have learned when and how to start smoothing the surface so as to lessen the tendency to bring fibers up.

At least you have a roof overhead, so having rain cause a pitted surface shouldn't be a problem.

LittleWheelsandBig

  • Whimsy Rider
Re: Concrete floor inside a shed
« Reply #11 on: 02 October, 2021, 09:52:57 pm »
Scoring the surface = 25-33% of the slab thickness, otherwise there is a fair chance of the slab cracking at alternative locations.
Wheel meet again, don't know where, don't know when...