The Brew Cabin

Posted: **Mon Feb 10, 2020 5:37 pm**

Dear Tony,
It looks like the patio I mentioned earlier regarding where to put the slot drain is going to be next to the house and falling to a gully. So the patio is falling towards the house unfortunately, aiming for 1:60.

The patio is going to be about 6m across the house wall and 4m away from the house (simple rectangle). Should the patio itself have both the transverse and longitudinal falls or should I aim for one fall such as follow the fall of the slot drain?

There is about 1m of land before the boundary on the left and about 3m of land before the boundary on the right. Does this suggest a fall perhaps in the middle where one falls to the left and the other falls to the right?

Or should I just have a fall towards the house?

Could I also ask about the slot drain here? It appears cleaning , say the ACO type , is very difficult. I have seen more expensive varieties where a paddle is inserted and moved along the slot. I don't think ACO can allow this. How do people with ACO type slot drains clean them?

Posted: **Sat Feb 15, 2020 10:53 am**

You can use 'complex fall' - a combination of transverse and logitudinal. If you checked the levels along any one edge, it would be consistent and in the one dimension, but the main fall would actually be diagonal.....

....so while you have a measured fall of 1:60 (or so) along any edge, the greatest fall is actually diagonal, at 1:44, so any surface water would follow that path, rather than strictly follow the edges.

Posted: **Sat Feb 15, 2020 3:08 pm**

Thank you very much for your reply Tony. Your reply took much longer than the other prompt replies so I am wondering whether you were inundated with messages or you were unwell. I hope you were not under the weather.

I don't think I can incorporate 10cm fall across the house boundary of 6m. I want the patio to be 15cm below dpc so with a fall of 10cm, parts of it will be 25cm. I am thinking of just a straightforward fall towards the house. I am thinking of deck-a-drain or NDS micro from your recommended drainage-channel website. I thought these are narrow and so unobtrusive and I am going for a flexible construction so dpt1 and sharp sand. We have never had flooding and much of the rain water can permeate through the jointing.

I am not sure which one to choose: deck-a-drain or NDS micro. The latter is narrower with more fittings but the former appears to be made by a company in Rossendale which is where my grandparents used to live. I have fond memories visiting them. I think the fall for the drain can be just 1:200 which is 3cm across the 6m.

The Brew Cabin

Transverse and longitudinal falls - Are they both required