Porous sub-base - Suds and the like

[wuciwug]

Hi,

It seems whatever driveway option I choose (grass, paving etc) assuming I have a porous 'top coat' surly I need a porous
sub-base to - otherwise I've just created a very high, big flat soak-away with no holes in the bottom only the sides (also known as the house.........)

are they all porous?

[Suggers]

Surely you understand what porous means?
Type1 as a sub-base is obviously porous, whereas a lump of concrete ain't, and needs adequate falls and drainage.
Or am I missing something? ???

[lutonlagerlout]

most sub bases are porous,because they comprise unbound material such as crushed limestone or such
regards LLL

[Big Phil]

most quarries produce a 'reduced fines' subbase, or it can be quoted as Type 3 Subbase

[GB_Groundworks]

or 803 i think is permeably? different names for same stuff

[wuciwug]

Ok, I was just unsure but I get it now, any what I would term hardcore (i.e lots of bits of stone / rubble compressed down to make a base) can be considered porous.

[Big Phil]

GSB Type 1, 2, 3 & 4 all have slightly different gradings and property requirements.

water will always find it's way down to earth. the grading of the material depends on how quickly you want the water to drain - the less fines, the more porous.

[MBPM]

Hi,

It seems whatever driveway option I choose (grass, paving etc) assuming I have a porous 'top coat' surly I need a porous
sub-base to - otherwise I've just created a very high, big flat soak-away with no holes in the bottom only the sides (also known as the house.........)

are they all porous?

Hi,

When I did our drive earlier this year I used Type 1X, which is like Type 1 but is twice the price, allegedly more porous and not available from any sodding builders merchant. If I had to do another project I would just use Type 1 personally. Either that or 10:63 graded aggregate as used under some permeable block paving systems, if appropriate.

More importantly I would say is the sub grade, ie if its clay you're going to end up with a pond anyway.

See Tony's page on soakaways as well.

[Big Phil]

Type 1X is yet another term for reduced fines subbase - very similar to (if not the same as) Type 3. This should be available from most quarries.

if you can blend 3 parts Type1 to 1 part 20/40 effectively then you'll end up with a similar material.

[ALG]

Type 1X is specified in the 800 series of the spec for highway works.
Type 1 reduced fines is not.

Type 1x therefore has to be non frost susceptible and reduced fines do not.
For driveways etc asking for reduced fines type 1 would be perfectly fine and cheaper.

[Big Phil]

I'd check the year of issue of your 800 series as i'm sure Type1X disappeared some time ago. it is now specified as Type 3. terminology remains tho in the industry and to be fair the material doesn't really change even if the 'new name' is different with spec revisions.