Laying a 5mx5m Concrete Base - lots of questions

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Hi All,

This Easter, I am going to try and lay the concrete base for my Log cabin. I am purchasing and building in the summer. So far I have had 1 quote which included some tree clearance and breaking up a previous base and small patio, which came in at over 5k!!!!!

So I am going to do as much of it myself. Yesterday I started to remove some bushes and trees, which went quite well. I am carrying on and removing the stumps today. I will be then taking down one of the 2 existing sheds and looking at breaking up the base. As I am a complete novice when doing this, I have a few of questions.

The larger of the 2 sheds is still being used. If I empty it, are sheds moveable in one piece??? I still need somewhere to store all my crap between taking up the old base, laying the new base and putting up the cabin? Idea was to put shed back temporarily on new base while I wait to but the cabin up.

Is hiring a jack hammer the best way of breaking up the bases, or seeing if I can hire a man and a mini digger to do it? Again I have never done anything like this before...

I have a bunch of old bricks etc. Could I use these if I smash them up as part of the hardcore for the base? Will it realistically save me any cash vs time to smash up? How much hardcore would I need? Also DPM - can I join 2 bits of dpm together and still have a waterproof seal? I can only see dpm in 4m wide rolls.

What is the best way of creating a form for this size? Do I need to try and get 5m long bits of timber or can I join 2 together to create the 5m length? should I hire road forms instead (look Ma I can google :)) Also what do I do about screeding the top top of the concrete to make sure it is level? Do I need to find a straight edge that is a bit longer than 5 meters? Any ideas??

I am also going to use the base as the floor to my cabing, so I am going to use a float to make it super smooth. Again I am going to hire one I think.

Also for the base I can also buy from the cabin company a composite foundation beam (https://www.tuin.co.uk/Composite-Profiled-Foundation-Beams.html) so that the timber will never be in contact with the base. I presume once it it in place I can seal around the foundation beam to stop any water ingress. What would be the best thing to use to seal?

Think that is it for questions for the moment. Any help would be greatly appreciated..

Nick
 
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Using a mini digger will be easiest and you can dig it out at the same time. A day will see both done.

The form can be joined pieces of timber.

As for screeding it will be very hard work at that size. You could use a centre piece on your form to split it into 2 2.5m widths but this will leave you a joint in your floor. If you do try and do it in one hit get at least 2 helpers and work off the edges first, screeding that much will be super heavy and hard work.

Dpc can simply be over lapped by 18".

As for the magically profiled base offered for sale it will not keep water out. You can not simply hope a bit of sealant will be it water tight.

If you want the concrete to be the finished floor you need to carefully think about waterproofing the wall floor junction properly. In an ideal world the concrete would be the exact size if the cabin minus 2" all round. That way the cladding will shed water over the edge of the slab.
 
Th
Using a mini digger will be easiest and you can dig it out at the same time. A day will see both done.

The form can be joined pieces of timber.

As for screeding it will be very hard work at that size. You could use a centre piece on your form to split it into 2 2.5m widths but this will leave you a joint in your floor. If you do try and do it in one hit get at least 2 helpers and work off the edges first, screeding that much will be super heavy and hard work.

Dpc can simply be over lapped by 18".

As for the magically profiled base offered for sale it will not keep water out. You can not simply hope a bit of sealant will be it water tight.

If you want the concrete to be the finished floor you need to carefully think about waterproofing the wall floor junction properly. In an ideal world the concrete would be the exact size if the cabin minus 2" all round. That way the cladding will shed water over the edge of the slab.
Thanks for the reply. Will definitely take.on board about the base being smaller. I think that the cabin company say that it needs to be 4.8m x 4.8m, which will be exactly the same size as the cabin.

Also should I look at possibly insulating the base?

Thanks. Nick
 
That size of base dont forget the

Reinforcing

Both mesh (the whole are) and some bar (Bar only around the edges - 6 to 12 inches in from the edge)

Otherwise it will crack and move over time.

I'd be looking at something like 6inches thick as well.

With the area you have posted - Plan to use 4 Cu Metres of concrete
 
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To be honest the easiest way is to pour the slab a little big and then cut it to exact size with a stihl saw once you have your base on site.
 
With the brick you want to crush up, i'd say no
The reason being is that it can float when you are screeding the top. There may not also be much room if your going to run steel mesh

If you were going to do it it would have to be very small and clean - not worth it IMO

With the screeding you could just make something that is 5m long and straight. Although easier said than done.

Like to see some pictures
 
Also should I look at possibly insulating the base?


Only if you're putting underfloor heating in this shed..

6 inches thick is a bit overkill if it's only going experience foot traffic. If you're parking a steamroller in there then maybe consider 6 inch.. At 4 inch you'd be looking more like 2.5 cube. Not quite sure what wgt means when he says it will move. Last I checked all the concrete I've poured over the time hasn't walked off..

Consider hiring a roller striker; the can be used to easily flatten off a 5x5 pad in a one-er, with just two people
 
'Crack & Move' – A large area like 5x5mtr square will be affected by how the underlying ground dries; during dry periods the edges will dry first and the ground will shrink leaving the edge unsupported – particular if the subsoil is clay based. That shrinkage will cause the concrete to be unsupported starting atthe edges hence leading to cracking of the concrete, most likely across the centre of the base. Unreinforced dust or larger particles will get into the cracks and once the ground expands as the ground absorbs water during wet periods the base will become supported again the dust or fill in the crack will cause the concrete to move apart. Over time those cracks will expand; also the original flat, level concrete base may develop a 'hump' in the centre with the crack being the high point.

Just the weight of the concrete alone over that area will cause it to flex and crack over time.



I suggest that 6 inch thickness of concrete is about right as you need a thickness around the reinforcing to prevent it breaking. Certainly 4 inches I'd regard as the absolute minimum.

I can only speak from experience...
 

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