Spec for permeable hardcore

21 Jul 2019
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United Kingdom
I want to build a tiny raised parking space where I currently have a yard. It will be approx 5x2m and some builder friends of mine have offered to do the work. To avoid having to go to planning I would like to make it permeable. Apparently this means the cheapest option is MOT type 3 hardcore - possibly finished with some gravel on top. My main question is can anybody tell me exactly what constitutes MOT type 3? Is there a specific size range and material? My parents have a load of hardcore they've just dug up and I was going to sift through and rescue what I could to use in my drive but not sure what I'm looking for.

If anyone knows too - my plan is to dig down through the concrete yard that is currently there to soil, pop down a permeable membrane inside retaining walls and then infill with the hardcore. The soil here is clay though - so how permeable this is actually going to turn out to be I will only find out once we dig down. If it doesn't drain well can I just connect an overflow pipe back to my rain water collection pipe which is close by? Does this sound like the cheapest and easiest route to getting the job done?

Many thanks!
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You could make it non porous and run off to a soakaway.

Prob cheaper than permeable SUDS compliant
Cheers Notch7- but its a tiny space - the yard is all I have at the front and is basically all going to be made into the parking space I want - so no room for a soakaway into a bed or something. The only thing I can do in the space is run off to a drainpipe for rainwater but don't think that would be enough to be SUDS compliant?
Sorry to hijack your thread. Is MOT 1 really non permeable? I'm having my drive done in October 6" MOT 1 and 2" Gravel using gravel grids with attached membrane. The drive slopes to the house slightly builder says drainage not needed as it's permeable?
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Any hardcore and gravel top is porous. Something to do with all the little gaps in it. :rolleyes: Non of that SUDs nonsense is necessary.

BTW, wouldn't a "raised parking space" require planning permission anyway?
Cheers Woody. Would you say that was true of any material then - such as bits of brick and concrete - as long as above a certain size? Or do you just mean all MOT grade 1-3 aggregates are all permeable to a greater or lesser extent? Any idea what size minimum?

The parking would be level with the road - but I would have to raise up my yard by maybe 30cm or so - does that need particular planning even for a permeable to you think? :unsure: Hoping not as when I went to the planning office to enquire he said they didn't tend to look favourably on tight parking spaces.
Any granular material is permeable and meets the requirement.

Strictly any raising of ground, especially if it involves construction of walls, or terracing of ground is classed as engineering works in the planning world and it is this that needs permission. If you are just raising a bit of ground in a dip, then probably not. But it's fact and degree.

Getting a car of the road for parking is always a good thing for planners, so they do tend to like to accommodate proposals.
Cheers Woody - not what I wanted to hear but good to know! I did pop into the planning office last week and spoke with duty planning officer and tried to show them what I was thinking of doing - I said it was thinking to make it permeable and so didn't think it would need planning and he seemed to agree - but perhaps he didn't understand - I guess I'd better get back to them.

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