The Brew Cabin

Posted: **Wed Jun 03, 2020 1:19 pm**

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

Posted: **Fri Jun 05, 2020 2:48 pm**

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.

Posted: **Fri Jun 05, 2020 6:40 pm**

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

Posted: **Mon Jun 08, 2020 11:54 am**

Siry - I misread that bit!

Posted: **Mon Jun 22, 2020 2:26 pm**

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

Posted: **Tue Jun 23, 2020 9:37 am**

Yep - that should be OK.

Posted: **Tue Jun 23, 2020 6:00 pm**

Thanks for your reply.

Posted: **Sun Jul 19, 2020 3:19 am**

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?

Posted: **Mon Jul 27, 2020 5:36 pm**

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.

The Brew Cabin

Preparing sub-grade and channel drain installation