The Brew Cabin

Posted: **Fri Jan 28, 2005 5:15 pm**

Say you construct a car park with standard:
25mm Wearing Course, 50 Base Course, 200 Type1, Geotextile.

The top WC and BC are impermeable, yet everything below is permeable.

So why can't you stop short of your edge with the WC and BC? The run off would drain to the edge through the Type 1 past the geotextile and infiltrate below.

Saturation of the subgade / subbase and loss of strength supporting the WC / BC ?

Posted: **Fri Feb 04, 2005 12:00 am**

You guessed correctly!

It is possible to design a sub-base suitable for drainage, but they're usually more trouble than they're worth. We use them with permeable macadam and permeable block paving, but they're a bit unpredictable and best left to carefully designed schemes where you can blame some eejit in the drawing office when it all goes wrong.

The Brew Cabin

Using subgrade / capping as soakaway storage - Can the foundations have a dual purpose?