Raised patio fill up

Hi

We want to extend our raised patio over the adjacent flower bed. For this we have build a retaining wall enclosing the flower bed. The maximim depth of the void is approx 600mm . We will lay sandstone on wet mortar.

The next step is preparing the sub-base. I see the following options for fill up:
1) MOT 1 and compacting
2) clean stone. I have already started with some small gravel along the edge. Next fill up will be 20 or 40mm clean stone
3) concrete

I prefer to go with option 2 since it seems to be easiest and cleanest. Do you have any experience with such a sub-base? Do I need to consider any membrane?

Cheers

Ricardo2019 said:

Hi

We want to extend our raised patio over the adjacent flower bed. For this we have build a retaining wall enclosing the flower bed. The maximim depth of the void is approx 600mm . We will lay sandstone on wet mortar.

The next step is preparing the sub-base. I see the following options for fill up:
1) MOT 1 and compacting
2) clean stone. I have already started with some small gravel along the edge. Next fill up will be 20 or 40mm clean stone
3) concrete

I prefer to go with option 2 since it seems to be easiest and cleanest. Do you have any experience with such a sub-base? Do I need to consider any membrane?

Cheers
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I did something similar years ago and was advised to dig out any top soil and organic matter down to a hard base. Stone will be ok as long as you aren’t left with void space between pieces for your mortar to disappear into. Compact your stone and fill with type 1 or some other appropriate fines, and compact again.

Sorry-no idea how I managed to repeat your post in my response!

Thanks for your reply. Do I really need MOT 1 on top of the clean stone sub base? Or can I just mix up a thick layer or mortar and lay the sandstone there? Also is there any membrane necessary?

Cheers

Type 1 isn't expensive and you'll be glad you spent the few extra quid when you see it (or sharp sand if you prefer) disappear into the gaps instead of your mortar. Assuming your base is prepared properly and your mortar is good, then no you wont need a membrane. Be sure to show us the finished product