Retainer wall - help required

[OllyH]

Hi all,

I am going to embark on my first bricklaying project, two small retainer walls in my back garden.

I have a small rectangular bi-sected garden (terrace house) with a slight fall towards the house. The garden has a wall along one side and back end with a fence the other side and a few decorative bricks to stop the soil going onto the path at the front (house) end.

I am going to patio the whole area and as there is a fall towards the house I am going to overcome this by laying topsoil down to take the fall away from the house and back to the end wall.

To hold the soil at the house end I am going to build two retainer walls with steps in the middle which will lead up to the patio.

My questions are:

1) Do I need to tie the retainer wall in with the 100 year old side wall or can it just be built up against it?

2) If I get the topsoil down and create the fall away from the house and to the back wall what type of drainage should I put at the end wall. Would leaving a small section running along the back of the end wall with gravel suffice for drainage?

3) Regarding question 2, can I keep the fall towards the house and put drainage into the retainer walls. If I did this would I need to leave soil/gravel behind the retainer wall in between the wall and the path so the water doesn't just go strainght onto the path and then the house?

4) Which of 2 or 3 is the best option

Many thanks for your time in this and your help expertise/options would be very much appreciated.

Olly

[Tony McC]

1 - I wouldn't tie-in any retainer wall as that could transfer stresses and strains to the old wall which might not be capable of withstanding them. The retainer wall has to be 'self-sufficient'; that is, it has to be capable of retaining the earth behind it without relying on any other structures.

2 - we don't know how free-draining is the existing ground. It might be that the site is thirsty and simply running off the surface water would be adequate, but until you determine the nature of the ground, it's all a guess.

3 - if you backfall towards the house, you need a linear channel of some form to collect the water and lead it away. But to where can it be led? If the ground is permeable, a SUDS installation or a soakaway would be the best option, but failing that, you'll need to connect to the existing SW system, if that's possible.

4 - No idea - not enough information at this stage.

[OllyH]

Hi there, thanks for your advice. Since posting here I have been told to level the fall out using ballast not topsoil to make the drainage better. I was going to have the fall away from the house and towards the back wall. I was going to have a slight fall to allow for the water to drain between the slabs as it runs off and then into the gravel if needs be.

Thanks for the advice regarding the retainer wall. I am just going to build in piers at the ends.

Do you think the above will be ok?

Cheers

Olly