Preparing sub-grade and channel drain installation

[JJBB123]

Hi,

1. My sub-grade is now almost ready, before putting in the sub base is it best to install the channel drain that will fit between my porcelain patio and astro turf? The drain will be fitted where there is a step in the sub-grade ( see photo 1)


2. My sub-grade isn't flat and has some small holes in it, is it best to backfill these with some gravel/sand/type 1 before fitting the geotextile?

3. I have some waste pipes that are 80mm below the level of the patio, I will not have room to cover with mot type 1. Is it ok just to cover with sharp sand? (Photo 2)


4. I will be fitting a retainer out of concrete for the sub base next to the neighbours fence but the concrete gravel boards will be higher than my patio due to the fall (yellow string line close the the fence), I assume the only way to hide this is to have edging stones that will be higher than my patio? I did not want these type of edging stones, any other suggestions? (Photo 3)

5. In the opposite side of the patio my neighbors garage is is on the border of my patio, I'm I able to use their wall as a restraint for my sub base or would I have to install a retainer? The garage on the right can also be seen in photo 1

Many thanks

Any advise would be much appreciated

Photo 1 https://photos.app.goo.gl/6U9wwdJKy6MvzPsb7
Photo 2 https://photos.app.goo.gl/MpQFotR6mAAxA2JXA
Photo 3 https://photos.app.goo.gl/YugEG4GvmUcjJd7N7

[Tony McC]

1 - always fit drainage *before* laying paving

2 - why is a geotextile being laid *over* the sub-base? Waste of time!

3 - This has been covered dozens of times in recent months. Cushion with sharp sand.

4 - You need some form of edging, flag-on-edge, dwarf wall or similar to prevent those grabvel boards becoming undermined.

5 - you are allowed to place loose material, such as a sub-base, against a neighbouring structure, but any bound surfacing (concrete, macadam, resin bound, etc.) must be isolated from the wall in some way.

[JJBB123]

Thanks for your reply.

2. I did mention that the geotextile will go over the sub-grade, I know it's no good over the sub base. Just needed to know what would be best to back fill the small holes/uneven areas in the sub-grade before fitting the geotextile under the sub base.

Thanks

[Tony McC]

Siry - I misread that bit!

[JJBB123]

Hi,

For your answer on no.4, could I use a mass of concrete with a granite kerb/edging stone on top? The depth between the sub-grade and gravel boards are between 25 and 30cm?

Thanks again

[Tony McC]

Yep - that should be OK.

[JJBB123]

Thanks for your reply.

[JJBB123]

Hi,

When laying the concrete for the edging stones, would I need to put anything over the SUB-GRADE for it to bond to the concrete?

[Tony McC]

No. It doesn't so muuch 'bond' as 'key in' to the sub-base aggregate.

Of course, there is *some* bonding but the main traction is via keying-in to the uneven sub-base surface.