5.5x4m Log Cabin Concrete Base

snappyfish · 18 Jun 2017 at 14:35

Need some advice.

A local builder I have asked to quote for a log cabin base size 5.5x4m

His points.

Needs a concrete pump from just outside rear access as doesn't want to borrow in that much (fair enough)
Didn't mention using any hardcore stating will just dig out and see what's there but tamp it all down.
Said he would go 4" deep at first ( I said why not 5")
Will use reinforced mesh
Will use a DPM

£1200 tp £1300 (he quoted £500 to £700 on phone)

All this sound right? I presumed a compacted hardcore base is a must?

Thanks

snappyfish · 18 Jun 2017 at 21:18

MikeB said:
He is talking in metres, you lot in feet

Definitely Metres yes, 5.5m x 4m roughly 18ft x 13ft

snappyfish · 19 Jun 2017 at 12:22

Furton said:
I've recently had concrete delivered for a retaining wall trench and the minimum order was only £120, and that's barrowed and leveled in, well worth it.

So a local builder did it for you?

snappyfish · 20 Jun 2017 at 12:07

Getting quotes of around £1100 all in, probably just going to go with that.

The cabin is due in July and running out of time, the guys quoted do a lot of this type of work in my area seen their fb page and website, so still not the cheapest, but coming in with small digger, all rubbish will be taken away. Less hassle for me and they seem to know exactly what's needed.

Thicker slab round edges compared to the centre where all weight sits. Will make sure it sits in right place just out of ground enough to stop rain splashing back onto the base form area around it. Will put some mesh in for sake of £40 and use dpm.

Cash job has lowered their quote quite a bit from £1600

I'm happy with that.

snappyfish · 28 Jun 2017 at 09:30

Quick question.

The base is started shuttering and hardcore in, I asked about DPM and they said "Id consider leaving one out, as the cabin sites on bearers and has a floor it's going to make no difference and will only take longer for concrete to dry out if wet"

Any thoughts?

snappyfish · 28 Jun 2017 at 10:40

rexehuk said:
This. Framing up, peg it outside. Put hardcore in, get mixing! Could just rent a mixer which will make it a bit easier, mixing it all by hand on a board is back breaking but worth it.

A pump sounds.... expensive.

Job has started now, dont have time myself, this below is new question..

The base is started shuttering and hardcore in, I asked about DPM and they said "Id consider leaving one out, as the cabin sites on bearers and has a floor it's going to make no difference and will only take longer for concrete to dry out if wet"

Any thoughts?

snappyfish · 28 Jun 2017 at 10:40

Entai said:
For your application I wouldn't bother with a DPM at all. Finish the concrete level with your lawn, then rest the timber beams of the hut on plenty of blue engineering bricks rather than wooden bearers. These won't suck up moisture like bearers would, and pass it into the wooden frame of the shed, but will still allow a little airflow under the hut, again to keep moisture levels down.

A lot of times, a DPM is used under concrete slabs not to stop any moisture coming through it long term, but rather to slow down its curing when it's being laid, by stopping the ground sucking all the water out of it. This helps the concrete base to reach maximum strength, which for a shed base is hardly critical.

Job already started, will be an inch roughly above lawn... The dpm is only concern at the moment.

snappyfish · 28 Jun 2017 at 12:06

Entai said:
As I have said DPM should not be a concern it is pointless on a job like this.

I then just went on to explain why its pointless on a job like this, and what you should look at doing later to alleviate any concerns over damp.

Sorry quoted in incorrectly. Thanks for input..

snappyfish · 29 Jun 2017 at 20:46

So someone else has mentioned dpm is needed if not for damp but to stop moisture being sucked out of concrete to quickly when curing?

snappyfish · 30 Jun 2017 at 19:26

Entai said:
One thing I would say is why a concrete base at all ????

Seems huge overkill for a log cabin or garden shed.

We had several sheds, greenhouses and a cabin in my parents back garden, and all were laid on paving slabs on a sharp sand base.

None had any issues for over 20 years.

Becuase 90% of the log cabins (sheds) I see have concrete bases, it's also recommended every where.

snappyfish · 30 Jun 2017 at 19:28

Hedge said:
Do you mind adding photos of finished job as I need similar in my garden. Thanks

Can do, not arriving until sometime mid-July, then will build when having time shortly after.

snappyfish · 26 Jun 2018 at 21:37

Freya13 said:
I got a garden room built recently, it's great as I have literally transformed it into an office for me and my husband. I got Bakers Timber to do it, and I am truly impressed by their work.

Seem them. Nice work on You Tube.

I thought I was clever and got someone to do concrete, and someone else to build it as I didn't have time! End result was around 6k then I had to take whole think down and rebuild it and build a sub frame as concrete was 100mm to 200mm to wide.

snappyfish · 10 Jul 2018 at 12:23

Abyss said:
I'd agree there is some over engineering going on here.

All of the holiday parks with huge 2-3 bedroom log cabins I've been to are just sat on breeze blocks / paving slabs. A concrete slab with rebar and a DPM is overkill for most ground conditions.

I also wouldn't want the cost of getting concrete pumped in.

One solution I have been looking at is ground screws. Still overkill but no mess, removable and quick:
https://stop-digging.co.uk/
https://www.groundscrewcentre.co.uk

For a 5.5mx4m cabin you'd probably want 16-20 ground screws so about £600 plus some weed membrane and pea shingle to finish the area off.

Great idea this, wish I has done that. Builders made concrete 200mm to wide all round, water run under cabin. Tried cutting concrete back didn't work, took whole thing down and now on paving blocks on subframe.

Cost a fortune, time and effort. Tradesmen were awful as I took there advice. Still not great! But lesson learned!