Laying slab base on really muddy, clay soil

[markyd1977]

This is what I was planning, would appreciate your thoughts please...

I'm putting up a summer house soon and wanted to put in on a slab base. The summerhouse is 4m x 3m, the base will be sized accordingly.

I was planning on digging down 130mm, laying 70mm of type 1, then putting the 32mm slabs on 30mm of cement, not dot and dab, but cement under the full size of the slab. The garden is on a slight slant running from back to front and from the right to left. I'll need to dig about 200mm at the highest point

First question is does this sound reasonable? Second question is, is 32mm slabs too thin for the weight of the summerhouse?

This is where I'm at so far...... It rained about 3 days before I started to dig. I'm down to my 130mm give or take, and I've dug up about a quarter of the overall area..... My soil is clay and muddy, even though the rain stopped 3 days before I started to dig. I left what I've dug out so far for 2 days to see if it dries out, if anything though it's gotten worse, 10mm puddles are now forming in some of the areas I've dug out.

What's my options (within reason)?

Would adding lime help?
Can I pile on the type 1 and hope it dries out?
Should I call it quits?

Thanks

 

[Ian H]

I’d put down a membrane before your type1.

 

[markyd1977]

Cheers. I'm assuming geotextile and not one of those crappy weed membranes? Would it be woven or non woven? Do you also think I'm okay to compact the type 1 with the water on the top of the soil or should I wait until it disappears? I have a feeling it'll be splashing all over the place

 

[Celeronmanuk]

Non woven. We used drivetex for a similar project as we already had it. It's really strong stuff.

We dug to 150mm and put in 100mm mot type 1.

 

[markyd1977]

Thanks. Do I need to do anything to the soil beforehand as it's so soft... compact it a little? Cheers

 

[Ian H]

I would scrape the top off it. I did some on mine the other day and had to scrape about 10mm of slop off.

 

[markyd1977]

Awesome. Sounds like I'm all go to go then. Thanks very much.

 

[Celeronmanuk]

We just scraped the soft mud off the top of ours too. Dried out pretty quick in the sun anyway.

 

[markyd1977]

Tell you what though, no wonder all those YouTube videos have timelapse when they're digging the base out, this thing is taking forever.....and the amount of soil is unbelievable. I took a rotavator to it to make it easier but the old back isn't up to it anymore!!

 

[Celeronmanuk]

Tell me about it! We dug out about 35 tonnes for our patio and retaining walls. Barrowed to the front up a tricky slope.

 

[JohnD]

Thanks. Do I need to do anything to the soil beforehand as it's so soft... compact it a little? Cheers

drylean mix and compact it down tight

edit

that's funny

I thought we were back on this thread

https://www.diynot.com/diy/threads/flooded-trenches.549190/#post-4685817

 

[markyd1977]

Unfortunately I was travelling for a few days so had to take a break from digging....came back to this after 2 days of rain. I'm concerned that anything I lay will get waterlogged......the deepest part is about 10cm

 

[Celeronmanuk]

I've not had experience of trying to get a slab down in waterlogged ground so can't really offer much. Maybe groundscrews?

 

[Mike13]

You could always try using an auger to make 6" dia piers for the slab to rest on, if they go down below the frost line the base should not move so much later on.

 

[markyd1977]

Decided against slabs now. Going with breeze blocks instead to lift it off the ground a good bit. Will put some decking boards around the bottom as a skirt. Still putting 2 ton type 1 down then the breeze blocks concreted on top. Also going to run a drain from the bottom left corner (deepest water point) to let any water out.