The Brew Cabin

Posted: **Sat Apr 30, 2005 1:31 am**

This is a great site. I have been using it for a couple of months to get my patio project off the ground and now the time has come to ask a specific question.

This is my first post so be gentle!

I am laying a reasonably large patio (25 Sq M) with 3 rows of terrassed steps leading up to it (each 5 m long). The ground it is being built on is heavy clay. I have already dug out all the top soil and pegged out the area to be covered. The garden slopes significantly towards the house (although the pation will not make any contact with the house) and I will be installing a land drain to deal with the surface water.

My question is this... Due to the sloping nature of the ground, I need to make up a level of 0.5 metre in one corner of the patio (and only 0.2 in the other corner). Is it acceptable to use sub-base (DOT1) to make up such a level? I will be using a plate compactor and will compact after every 150mm.

Second question... Is there any need at all to install a membrane to avoid earth movement beneath the patio (other than around the land drains)

Thanks for your help guys!

Posted: **Wed May 04, 2005 4:27 pm**

No problem in building-up by 500mm as long as you do as you say and compact in 'lifts' of not more than 150mm. This works fine for heights/depths of up to around 1 metre.

As for the membrane, I can't say one way or t'other as I can't see the ground. I'd only use a membrane if there was an obvious need for it, such as soft ground. However, you can't balls things up by including one, as long as it goes in at the right place (between sub-grade and sub-base)

The Brew Cabin

Maximum depth of sub-base