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Preparing Sub-Base for Landscaping Project

Postby Danny-r » Thu Jan 27, 2022 12:46 am

Hi guys,

Just wanted a bit of advice on this. Fairly (very) new to garden landscaping but I'll give anything a go after a few Youtube video's. I'm at the stage where it's planned and will probably begin buying materials next week, to then begin the first stages in mid-February. This is one element of a larger project, but the rest is irrelevant.

Essentially, I'm laying a 2.31x2.31m sub-base. It will support an item that will weigh 1800kg with dimensions of 2.2x2.2m.

My plan at the moment is to dig the hole (of course), lay and compact 100mm of Type 1 MOT, and then place a pad on top of that which the manufacturer states can support 420 tonnes per square metre. The pad is usually able to be placed just on grass, however the manufacturer for uneven and/or areas with drainage issues to dig it out and use 50-70mm of Type 1, so I've gone a little more.

So, Type 1 for 100mm, a weed membrane, then the pad, and the gaps within the pad is filled in with gravel. Is the fact I have typical new build clay soil going to impact this? I need to make sure it's secure, I don't want it to sink! Would you make any adjustments to the process, or even go for more MOT?

Edit: Just to add, eventually, in the months after I'll be adding a decorative stone border around this area. Will this effect the Type 1, or will the fact I've compacted it in mean that even when I remove the soil around it and replace with stones that it'll be structurally sound?
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Simply Build It

Postby stoneyboy » Fri Jan 28, 2022 10:44 pm

Hi Danny-r,
What you propose should be ok but if you are using a pad capable of supporting 420 tonnes per sq m you will need to strengthen the lower layers just to support the pad alone.
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Postby Danny-r » Mon Jan 31, 2022 9:40 pm

Is that not the purpose of the type 1? To create a stable sub-base?
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