The Brew Cabin

Posted: **Tue Jul 06, 2010 11:03 pm**

I am in the process of planning a new patio and I have a bit of a dilemma as to where to drain to.
The patio will adjoin the rear house wall and extends 5.5 metres out and is 8 metres wide. Where the patio finishes, coming out from the house wall, it will meet a 2 metre high retaining wall ( we live on a steep slope coming down towards the rear of the house).
There are adjoining private properties on both sides.
We are on chalk subsoil.
Will it be sufficient to finish the patio 10-15cm from the retaining wall and dig a channel 30-60cm deep and fill the channel with gravel allowing the drainage to run into the channell and soak into the sub-soil?
I could drain towards the house wall and run a channel into the roof drainage system but I'm just a bit reluctant to drain towards the house.

Any advice would be much appreciated.

Thanks

Posted: **Tue Jul 06, 2010 11:55 pm**

it is awful steep in berko, sean
i worked on the flats by the canal years ago and apart from the main street and station road nearly all of the town is on a vertiginous slope
is your house terraced?
the main thing is, and you have made a good start, is not to ignore the surface water it has to go somewhere
a picture looking towards the back of your house would be helpful
but also bear in mind chalk is usually very permeable,a test pit will affirm/deny this
cheers LLL

Posted: **Wed Jul 07, 2010 10:52 pm**

Thanks for the advice LLL.

I've decided to run into the same drain that the roof guttering run into.

My reason for this decision is that the retaining wall foundations are so wide that the drainage gulley I had planned would have to be quite wide and a little unsightly.

Below is a basic plan of what I intend to do. Should I create a fall from the entire patio towards the drain or install a land gutter (is that the right term - one of those gutters with a steel grill cover) running perpendicular from the drain to the retaining wall to which I could create the falls.

-------------------------------Retaining wall
?
?
?
?
?
?
-------------house wall -X-- --shed wall

If i install the land gutter (where the question marks are) I intend to take a fall away from the house and shed walls and then sideways into the land gutter.

The alternative is to create a fall using the paving taking a small fall away from the house and shed walls and then sideways and down towards the drain. The paving is going to end up fairly close to the 2nd course down from the DPC so I intend to create a gulley (4" wide) along the house and shed walls , filled with gravel, to prevent any splash risk in heavy rain. I could create the same gulley around the drain, retaining the gravel utilising a metal mesh around the drain.

Do either of those options sound viable or does anyone have any better ideas.

Posted: **Thu Jul 08, 2010 12:13 am**

hard to say from your drawings but make sure you have at least 1:60 fall to any linear drains
using gravel as a drain is a fail,dont do it
150mm below dpc is fine ,you do not need any more than that
make sure your connection is trapped to stop leaves etc blocking the drains
LLL

The Brew Cabin

Where to drain to on new patio?