What type of stone?

For percolation ask whoever designed the percolation area what they want as there is actually a calculation to see how much water the stone will soak and there must also be x amount of space between the stones after filling has been completed. For argument sake when filling is complete the stone must only fill 60% or 70% of the volume of the excavation, or whatever the regulation is thus defining the type of stone used. It's very fussy but the last thing you want is an unhappy engineer. I've seen 2" to 4" washed round stone specified and I've seen 4" to 6" crushed stone specified. In my opinion 4 to 6 is much too big.

For footpaths just use 804 limestone and compact it well.

Penn wrote: »

804 is no longer used for footpaths. You need to use SR.21:2014 Annex E material (rolls right off the tongue)
https://www.nsai.ie/NSAI-Roads-Standards-Committee-Publication-of-S-R-21.aspx
https://www.roadstone.ie/faq/sr-21-faq/


As for the percolation trenches OP, I believe a 30mm pea gravel is generally used. But I agree that whoever designed the percolation system should be asked in case they based it on specific requirements.

I stand corrected on 804, things are ever changing!!