Concrete slab for garden cabin

Gaz

Hi all,
After seeing some crazy quotes (€1k - €2k) for a 4m X 3m concrete slab, ive decided to tackle this myself. Looking for some advice please.

After some internet research, ive come up with the following. Please correct/advise where needed ...

- Dig to 150mm
- Place and level wooden frame with steaks
- Lay 75mm of hardcore and compact with a tamper
- Add DPM
- Lay and level 75mm of concrete.

How does that sound ?
Should I use hardcore or just get extra gravel ?
Would a 3 to 1 mix for the cement be ok ?

Should I just hire a professional ? :pac:

RebelButtMunch

Dont forget to factor in the price of a skip if you need it

stiofan85

Doing similar myself and not too excited at the thought.

Not too sure on the concrete details though - doing my research also, so eager to hear what advice you get.

Think the only thing you are missing in steps is to square the frame (3-4-5 rule).

Calahonda52

note dpm in this link
https://www.rentokil.co.uk/damp-proofing/what-is-damp-proofing/

imo slab should be above ground and allow it to drain as u have no wall to protect it.

Danny Donut

Gaz wrote: »

Hi all,
After seeing some crazy quotes (€1k - €2k) for a 4m X 3m concrete slab, ive decided to tackle this myself. Looking for some advice please.

After some internet research, ive come up with the following. Please correct/advise where needed ...

- Dig to 150mm
- Place and level wooden frame with steaks
- Lay 75mm of hardcore and compact with a tamper
- Add DPM
- Lay and level 75mm of concrete.

How does that sound ?
Should I use hardcore or just get extra gravel ?
Would a 3 to 1 mix for the cement be ok ?

Should I just hire a professional ? :pac:

Gaz I did similar. Dug it out and then got a neighbour to help with the clever bits.

On the "Dig to 150mm" - I'd say its important to get all of the organic stuff (the top soil) out so you get down to the subsoil.

We did 150mm gravel and 100mm concrete. We put steel in it and had a slight run-off (40mm over 4M).

All the best

stiofan85

Danny Donut wrote: »

Gaz I did similar. Dug it out and then got a neighbour to help with the clever bits.

On the "Dig to 150mm" - I'd say its important to get all of the organic stuff (the top soil) out so you get down to the subsoil.

We did 150mm gravel and 100mm concrete. We put steel in it and had a slight run-off (40mm over 4M).

All the best

How long did it take two of you? Did you have a mixer or have concrete delivered?

I've no side access so would have to lug all the sand etc
.. Through the house

Danny Donut

Let me say at the start though that I'm probably in a different postion because I'm rural and ...

It took me about 5 days to dig it out, allowing for weather and the wife's missions in between.

Neighbour did the gravel and wacked it in.

Neighbour helped me set the wood in. I did the damp proof. Then the conrete was delivered. He smoothed it off and brushed the top off.

Took off the wood a couple of days later, cleaned them up and took them over to his yard.

stiofan85

Danny Donut wrote: »

Let me say at the start though that I'm probably in a different postion because I'm rural and ...

It took me about 5 days to dig it out, allowing for weather and the wife's missions in between.

Neighbour did the gravel and wacked it in.

Neighbour helped me set the wood in. I did the damp proof. Then the conrete was delivered. He smoothed it off and brushed the top off.

Took off the wood a couple of days later, cleaned them up and took them over to his yard.

Thanks. I've done the digging on my own. had 300-400mm of raised bed 7m wide to remove. Back is in bits after that. Struggling to face the reality of the concrete. Did a smaller area (maybe 1/3 size) by hand last year without a mixer. That was tough going too!

Have a couple of mates willing to help out but even just getting the sand and cement though the house seems daunting.

Chap selling the log cabin recommended a ground screw foundation instead but I am unsure about it. Also pricey for what it is.

Danny Donut

stiofan85 wrote: »

I've no side access so would have to lug all the sand etc
.. Through the house

Reminds me of when we lived in the smoke

In that situation - I probably wouldn't do a concrete base (depending what its for).

When I needed a shed in that situation I put down about 6 of the really thick (bloody heavy) paving slabs on sand as a base. Was fine for the 15 or so years we were there.

stiofan85

Danny Donut wrote: »

Reminds me of when we lived in the smoke

In that situation - I probably wouldn't do a concrete base (depending what its for).

When I needed a shed in that situation I put down about 6 of the really thick (bloody heavy) paving slabs on sand as a base. Was fine for the 15 or so years we were there.

Funnily enough, there is an ugly patio out the back with those exact slabs. She hates it. her hate = work for me usually....But I could potentially repurpose those slabs into a base. I'd still have to haul in sand but would be less work. Interesting!

Danny Donut

To my amateur mind that certainly sounds the way to go.

I'd baulk at the amount of material you'd have to drag through the house otherwise - the cleanup alone

listermint

Use the slabs as packing rent a mixer and do the rest. This is easy work it's not exactly rocket science. You have the skills for it . A mixer and you'll have it done in no time. And rent a wheel barrow and buy a roll of thick gauge polythene you can use some for dpc and the rest for the floor of the hall when bringing stuff through

Gaz

Thanks all.

Is a run off really required ? I understand the reasoning when laying a patio for example where there is the possibility of lying water but this slab will almost entirely be covered with the cabin, which itself will have a slight roof overhang and guttering. Would you still recommend a runoff ?

I would have thought a level slab was required for stable construction of the cabin.

listermint

Level is fine.

Lumen

I did this recently for an oil tank. Went with readymix concrete as after spending weeks clearing a hedge, replacing the fence that the hedge was holding up, digging out 2.5m3 of soil and roots, wacking the 804, making the formwork and cutting the rebar grid I just wanted the damn thing done.

Worked out great, ~0.7sqm poured in a few minutes, levelled and screeded at leisure.

Mine was poured below sloping ground (top of slab is at -100mm at one end and -300mm at the other) so yours should be easier.

In theory you're supposed to dig until you hit solid ground, but I think my clay goes to the centre of the earth so I gave up when I had space enough for 300mm of 804.

Don't forget spacers for the steel! Also, it might be tricky to get the steel at the right level if you've only 75mm of concrete, not much margin for error.

CJhaughey

Pieces of broken concrete tile work well as spacers for remesh.