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One's bum and things that bite you there!


MikeSharp01

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Although I have been away from the build for a few weeks due to to flu, work (yes I went back cos they asked me help out for a few weeks) and parties I have been back on the build for the last 5 days and have reached a harrowing conclusion.

 

The muck away costs for a passive slab are huge! The first lorry grab lorry turned up today and took 15m3 of soil which didn't even dent the pile and we have only done about 30% of the slab area, 600mm deep. When I worked out the budget for this phase I had reasoned that the existing property, a timber cabin, would be hollow down to the soil when in fact, as we demolished it we realised that it was on a slab with some massive foundations - no idea why. These had to be broken up first, and disposed of as rubble before we could start to scrape back the clay to the required depth for the slab build up to commence.

 

So I now think we will need between 10 and 13 lorry loads of muck away which is about 4x the budget I had worked out and will eat a second chunk from the contingency. The expansion (swell) of clay (40%) as you dig it does not help either. I noticed that the grab lorry has load cells, or similar contraption, so it knows just how much weight it has aboard and although we had the volume today we were well down on total weight. So my next job is to run up and down along the pile with the digger to compact it so that it goes back to around 100% before the grab picks it up as I don't think it will swell much in those jaws.

 

Moral of the story is - if you are thinking of a passive slab and you need to dig down, IE you are not building it all above ground, work out the muck away costs carefully.

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We have just finished day two and are still to complete the site clearance. The vegetation was removed first but we are having to scrape down some 12 - 18 inches of top soil to get to the sub soil. This has generated so much top soil, the space we had allocated within the plot was soon filled. Thankfully and I mean thankfully, the farmer has allowed us to deposit the remaining top soil in his neighbouring field as he will no doubt find a suitable use for it. I will post photos tomorrow after I have visited the plot but this must have saved me a fortune in removal costs. As @MikeSharp01 points out, you can never budget enough for ground works!!

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Makes me feel smug.  Even stripping all the top soil down to sub soil, and then digging the foundations, muck away =0.  The advantage of a sloping site and using all the excavated soil to build it up and make it less of a slope.

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What depth are you digging to, Mike?

 

I didn't do an exacting calculation on the cost of muckaway for my site as there are other (time) advantages for me with piling, but I reckoned it would pretty much double the cost of my original groundworks budget, and I'd been generous with that.

 

Even so, we will still need to excavate a fair amount to get the door of the house level with the site as the cellcore layer that soaks up the heave is of significant thickness by itself.

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Our one stroke of luck on the build was that the farm a mile up the road was making an earth bund around the bio-gas plant they were constructing.

As most of our excavation was heavy clay soil this was a godsend.

They were very happy for us to dump it for free.

Win win for both of us.

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Despite shifting over 1000 tonnes of material we were lucky that we had a borrow pit on site, we took out hardcore from the ground which left a big hole, we then took the clay excavated from our site and infilled the hole (also with over 100 tree stumps) and then put turf back on and you wouldn't know after 2 1/2 years. Could of cost £10,000's and might have killed the project before starting.

 

Until the concrete lorry came to pour the foundations no material was imported or exported despite the lengthily access.

 

 

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54 minutes ago, vivienz said:

What depth are you digging to, Mike?

The site slopes so at the rear of the site the dig is down 600mm at the front it is about 400mm, it is 15m long and 9m wide. So the volume, with swell, is  68m3 x 1.40 = 95m3 which is 7 x 15m3 trucks full.  Then there is the soak away (1 truck) and we have to remove about 30m3 (2 Trucks) of soil from the footpath. We have already sent 3 trucks of rubble away, who ever knew how much rubble a wooden shack needed.

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I think that we will be going deeper than that, even with our piling. We will be able to lose quite a bit of the spoil into the garden and possibly elsewhere on site but there will still be a fair few truck loads to get rid of.

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On the topic of wooden huts ours was sitting on this lot. 

 

So after removing all that lot, I have just discovered another set of foundations which we have been told may have been from the conveyor belt on site ? so could be any sort of thickness, the last lot I removed was just over 400mm thick. 

A237DB7E-3E26-4D90-A570-C7D89ABAC96F.jpeg

7F2DD84A-6052-4555-98CF-F5E0E69E858A.jpeg

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12 hours ago, MikeSharp01 said:

[...]

Moral of the story is - if you are thinking of a passive slab and you need to dig down, IE you are not building it all above ground, work out the muck away costs carefully.

 

We have a slight slope across the site. At first I thought time would be a problem. In this context it was the opposite. No spoil to be taken away.

A gently sloping site can be helpful.

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Not passive slab but our strip founds for house and garage produced about 100 tons of clay, we have a dead flat site but found a local farmer with an old quarry who said he would take it at £30 a trailer load (13tons). He said he would take it in the summer when the ground was dry, that was a year ago and he still can’t get on his fields because of the wettest year on record. I am praying for a drought this year to make up for it?.

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15 hours ago, Redoctober said:

Thankfully and I mean thankfully, the farmer has allowed us to deposit the remaining top soil in his neighbouring field as he will no doubt find a suitable use for it. As @MikeSharp01 points out, you can never budget enough for ground works!!

 

Last push today and the site will be cleared - Now that we have started, I shall update my blog over the weekend with some more photos.

DSC00475.JPG

DSC00476.JPG

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