Compacting a sub-base - Preparing for permeable

gisago · Post: # 42222Post **gisago** Fri Oct 09, 2009 12:13 am

Hi all,
I seem to have read in some manufacturer's literature or heard that the sub-base for a Permeable block driveway does not need as much, or any, compacting compare to normal blocks - the main wacking being done once all the blocks are laid.

Can anyone confirm this or put me right?

Suggers · Post: # 42223Post **Suggers** Fri Oct 09, 2009 2:26 am

No no no - you've misheard. The secret to any successful paving is always the sub-base - you've heard of the "house built on sand" ?
Check out -
Block paving
Also -
Permeable paving
All the best.
ps - it's a lot to read and digest, but worth it.

gisago · Post: # 42227Post **gisago** Fri Oct 09, 2009 11:20 am

thanks Suggers.....

I've since found the source of my info....
Tobermore have a pdf dealing with Hydropave and it says:

"because the material has no fines, it [the 20mm-5mm aggregate] does not need to be compacted in the usual way. However its particles need to be re-oriented to ensure that they occupy the least volume"

So they seem to be going all round the 'ouses to say compact the sub-base !!

They also say that the 6.3mm-2mm laying course does not need wacking, simply screeding - any comments on this?

DNgroundworks · Fri Oct 09, 2009 2:07 pm

Jesus 6.3mm?? who is going to bother for .3 of a mil? And a 2mm minimum, whats the point in that?

Pablo · Post: # 42291Post **Pablo** Mon Oct 12, 2009 10:02 pm

Re-read the PDF the 6.3-2mm is aggregate size. The 20-5mm course should be well compacted but the bedding grit should only be lightly run over. This is because grit is hard to screed if you compact it fully. Do the final bedding with a diesel plate.

Big Phil · Post: # 42300Post **Big Phil** Tue Oct 13, 2009 8:19 am

In English it's a 6mm single size, but EN Aggregate Standards call it 2/6.3mm. 20-5mm is now called 4/20mm (it's to do with maximum & minimum grading limits on nominal-size and under-size sieves). The EN Spec descriptions tend to cause some confusion as the undersize sieve on single sizes leads people to believe it's a graded aggregate.

6mm - 2/6.3mm
10mm - 4/10mm or 6/10mm
20mm - 10/20mm or 14/20mm
28mm - 20/32mm

20-5mm - 4/20mm
40-5mm - 4/40mm

40mm Down - 0/40mm

either way i'd expect some difficulty compacting a single size aggregate