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Groundwork & Foundations

Speed up the drying process of clay ready for a concrete pour?


“I am writing this on behalf of my brother Andrew who is hoping someone could give him/me a little help and advice.”

At the start of the year I posted an add on Facebook for a local gardener to do some general landscaping and garden maintenance on the front of my property as I am disabled and confined to a wheelchair, and over several months he would come by and mow my lawn and do some weeding, anyway we got talking one day about my back garden and he asked if I would like any work done on it, to which I replied no as it was completely inaccessible for my wheelchair as the area was at least 3 feet above the back doorstep, it was then that he said that he and a builder friend could completely drop the area level with my back door giving me full access outback and all it would cost me is £120 each per day, and that I would need to hire a mini digger and dumper for 5 days as they said that all the work agreed upon could be done in that time including building a retaining wall and putting down a concrete slab, and I would also need to hire a RORO skip, I told him that I would have a think and get back to him with a decision, a couple days past and I received a call from said gardener saying that he could start the project straight away as he had some time before his family holiday the following fortnight and that he could do with the work and money to pay for this and promised that I wouldn’t regret having the job done sooner rather than later, so I agreed and payed for a RORO skip and hired a mini digger and dumper for 5 days, and work started on my garden that following Monday and all was great for 2 days until they said that they underestimated the amount of soil that would need removing as it was mostly clay and not soil so 1 RORO skip turned into 4 RORO skips at nearly £450 each and a five day job turned into 13 days which meant having to extend the mini digger and dumper hire for that period, and then they told me that they could not get the project finished before their holiday and they would return when they got back this was 2 weeks ago and I have tried to contact them to no prevail there number is now dead and I can’t find them on Facebook, and my garden in like a swamp as it is made up of heavy clay, I was hoping someone here could help as I know nothing about landscaping and groundworks and am desperate to have a concrete slab down so I can get out and enjoy my garden but as the ground is like sludge and the clay is not allowing the rain to drain away I would like to know if it is possible to somehow speed up the drying process of the clay ready for a concrete pour?

Thanks for reading.

6 Answers from MyBuilder Groundworkers

Best Answer

For a slab installation ( if it’s sitting on top ) there really isn’t anything you can do.
The curing time for concrete poured directly onto the ground, will be slowed down, however it will sett.
I do suggest a steel reinforcement mesh is used, something like A142 at minimum, even a heavier gauge .
Try not to pour the concrete in rain, this will have an effect on its strength and finish.


Answered 20th Dec 2019

I would advise against pouring directly on to clay, there are many variables and different ways to pour/finish concrete so I won’t go in to too much detail but I’d advise to put at least 100-150mm of stone down and get it compacted prior to pouring the concrete.

Personally I would shape the whole area up with stone (recycled concrete i,e 2” down should be good enough or pay a bit extra for MOT Type 1) to leave enough to pour a 100mm concrete slab on if you are insisting on a level slab. This should also make it cheaper for you as stone isn’t as expensive as concrete.

A layer of A393 mesh in should make it more than strong enough, if anybody advises more than 100mm concrete I would question it simply because it’s not load bearing and the only traffic on it will be yourselves (I,e no cars etc).


Answered 26th Dec 2019

Sorry to hear about your experience sounds like you have been ripped off by some nasty people
You can turn it around and enjoy your garden provided you follow some basic guidelines which is imperative if you want to enjoy your garden for many years to come
Clay is tricky to build on as it holds the water and expands and shrinks/cracks like crazy,you will need to stabilise the area with compacted hardcore first and bear in mind that if you have a level threshold for disabled access then I would recommend putting in a line of heavy duty aco drainage adjacent to the rear of the property as the finished floor level of your new slab will be higher than the existing ground level thus providing a way for damp to enter the building above the damp course level(you can also prevent this by sloping away from the property and waterproofing the top 150mm of your existing brickwork)
It is recommended that the new concrete is reinforced and poured to a depth of 150mm to accommodate the excess movement from the clay,so you need to dig at least 300mm down to allow for hardcore and concrete, if you can afford it dig 350-370mm off then do hardcore ,reinforced concrete then slab on top of the concrete with nice paving level with your internal floor height and use a hidden aco drainage under the paving it will then look reallynice and you won’t transfer dirt/water into the house because the surface water drains away into the hidden channel(which must be discharged of properly into a soak away or acceptable manhole) and the 6”of concrete and 6”hardcore will hold up fine and provides an excellent base for the slabs/paviours
Sorry for the long winded explanation but it’s something i feel strongly about as my mother has polio and having had the same problems as you I know how much it means to her to have a nice,clean and sturdy wheelchair access into the garden especially in winter.
Hope this helps give me a bell if you need any further assistance I’d be more than happy to help


Answered 2nd Jan 2020

Make sure you put a layer of clean stone down and a layer of Teram and them 100mm of type 1 scalpings well compacted then 1200 gauge Dpm With a193 gauge steel for strength and make sure it’s put on 50mm feet so concrete flows under neath if it’s load bearing put c35 concrete in regards Matt


Answered 26th Dec 2019

Firstly I would go to trading standards, with regards to the slab, depending on the depth, but some 4 to 6 inches of crushed rubble and 3 to 4 inches of concrete, with mesh would do the trick as well


Answered 2nd Jan 2020

I would also suggest putting in a ground barrier fabric and crusher/reinforcement before concrete..
However this work would normalt req building control approval as you are altering the natural dtainage of the site and would probably req land drainage before any concrete overpour.


Answered 1st Jan 2020

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