I've been reading about retaining walls over the past couple of weeks and there's so much conflicting information out there. I know every job is different but every time I read a how-to it says something different.
anyway, here goes...I have an extension on the back of my house put up by the old owners in the 80s. That's fine but it looks like that when they dug out the footing, the earth they dug out they left in the back garden and stuck a few flags on it to form a patio area (if you can call it that!). The garden in general slopes up about a ft in height over a 25ft distance so not a huge amount.
The first two ft against the back wall of the extension however slopes down very slightly ( as it should two brick below damp course) then the slope starts rising all the way to the back.
Wanting a flat area, I've dug out a 10ft square patio area at the back of the extension (through various layer of s**te concrete that the lazy builders didn't bother removing) that slopes away from the house. I've measured from two brick below DPC the 30mm (flags) + 25mm(sand)
- 75mm(hardcore) and created a 25mm drop over the 9ft for drainage. That i'm not too worried about it but at the end of the 9ft is the rest of the garden where the grass was before I took the turf off.
From the height of the patio there will be about a 1ft to 1.5 from the top of the flags to the grass level. To compensate for this i'm going to build a small retaining wall and a step. I've dug the footings at the end of the patio 9in deep and 17in wide filled them with a 1:2.5 cement,sand mix.
I now plan on building a retaining wall of two brick thick with a top soldier layer as edging for the grass.
Some questions...
Have I gone about this the right way?? I also plan to leave vertical weep holes 1m spaced at 1 course about flag level of drainage??
Do I need a DPC for this, or as it's in direct contact with the earth there will be no point? or can you but a dpc along the back of the wall - but then how will it drain??
What happens if i render the wall ? how will it drain?
Would it be better to do a single skin of normal bricks and a skin of concrete blocks for greater strength??
Should i leave a gap between the two skins and fill it with mortar for stability ?
Should i join the two skins of brick together using butterfly wall ties for greater strength, stability??
Considering the height of the wall and the fact that it is only really holding back a ft and half height of ground am I going a bit overboard with all this.
Just want to make sure I'm doing the right thing.
Cheers if anyway can help!!
Jt