Geotextile underneath the sub base, help!

mashed13

Well,

I don't know if I messed up or not, there were divided opinions on the research Ive done prior too undertaking the project but now I have to question this again.

Im laying around 100-120sqm of block paving at the back of my garden, I excavated around 300mm filled it with 150mm of 804 subbase compacted, sand and paving to follow.

So long story short how badly I messed up for not installing geotextile underneath the subbase?? I don't expect any heavy traffic on it apart from it being used as walkways.

Day Lewin

Geotextile is vile stuff. I'm glad you didn't lay any.

What harm if some poor little plant with a tough attitude decides to try and grow in one of the cracks of your pavement?

This is a gardening forum: plants should grow!

magicbastarder

i don't think geotextile under 300m of hardcore, sand, and slabs would prevent much from growing!

what would be the logic of using geotextile under that? i'd have thought that 300mm would be enough for a road, let alone a patio.

mashed13

I wouldn't be too concerned about the weed growth as in theory the weeds on the paving usually grow from between the cracks with seed being blown on to it ,not from underneath.

My worry is with the movement of paving as in the subsoil may settle unevenly and couse movement in pavement, geotextile should prevent that..

standardg60

Don't use sand btw OP, lay the cobble on paving grit or crushed 804.

looksee

If the hardcore has been rolled it will not settle. You did not disturb the sub soil so it should not be going anywhere. I had gravel over a similar base - somewhat less if anything - and the only weeds that came were the few that germinated in the gravel and were easy to remove. Regardless of what you do there will always be a few weeds, just hopefully very significantly fewer than if you had not done the hardcore. You do not need the geotextile.

The Continental Op

The geotextile helps prevent the subsoil and subbase from mixing and helps spread the load so less subbase is required.

With mean use of subbase the geotextile separator becomes very important, with the amount of subbase the OP has used it really doesn't matter.

On an industrial site with heavy machinery trafficking regularly the geotextile comes into its own stopping the ground sinking as wheels go over which mixes subsoil with the subbase which leads to a muddy mess when wet. I doubt the OP is parking up a 22 tonne lorry ;-)

mashed13

Now I was originally going to use the grit or what you call them tiny washed stone, but after speaking to a few landscapers around, they told me that sand is superior and much easier to work with, is that a case? Any good soul could comment on this?

mashed13

https://www.boards.ie/discussion/comment/120705520#Comment_120705520

Thats the worry I had that soil will start to move, but I haven't really disturbed subsoil underneath and the patio itself won't be used for car traffic, fingers crossed all stays in place when done🤞

The Continental Op

The sand is fine, and much easier to work with imo. The fact its over 150mm of 804 is perfect. You aren't going to notice any shrinkage if you compacted the 804. 300mm is plenty enough to excavate into undisturbed subsoil.

standardg60

https://www.boards.ie/discussion/comment/120705610#Comment_120705610

I'd never use sand unless I was laying in concrete, it's far too maleable and likely to move and subside when wet used on it's own.

Grit or 804 dust forms a good static base when compacted, I'd rarely if ever see anyone use sand nowadays.