Garden retaining wall and drainage

[job_bodger]

Hi, I am hoping someone could answer 1 or 2 questions. I've never built a wall before so please have patience !!

I'm intending to build a retaining wall in the back garden out of common red brick. Basically at the moment my garden lawn is sloping towards the conservatory and abutting it above the damp course and moisture is starting to set in (and the garden lawn at the bottom of the slope tends to get water logged). To solve the problem I wanted to create a small path between the conservatory and lawn and build a 70cm high retaining wall so I can level off the lawn and stop it sloping.
What is the best method for this?

1 or 2 layered red brick wall ? Or 1 layer of red brick and 1 of breeze blocks ?

Do I have to back fill with non compacted clean stone for drainage ? If so what does this entail? Does the landscape fabric wrap entirely around the back and top of the clean stone ?

What should I use as foundation for the wall ? Concrete or compacted gravel ? I presume concrete, if so should it be 12 or 18 inches deep ?

Does anyone know of the typical problems you run in to ?


If theres any budding landscapers/builders out there any help would be much appreciated!

[matt h]

look at main site reference landscaping. LLL will be best to advise on wall connstruction, but the general drainage principles are on the main site.

[job_bodger]

Ok thanks, had a look around and some good information on retaining walls. Could I ask why the damp proof membrane needs to go on top of the back fill aswell on the sides ? Is it just to prevent any water getting in ? Can I just use standard 100g landscape fabric as the "optional filter membrane" ? Also do I need to compact the back fill as has been suggested on some sites

thanks

[Rich H]

The waterproof membrane doesn't go on top of the back fill, it just prevents water from being in constant contact with the wall as shown by the green line on Tony's drawing. The purpose of the optional membrane is stop the soil and gravel mixing which it will gradually do over the years. I haven't used one before as it's seemed like overkill to me.

I'd go with three courses of dense blocks (not brieze blocks!) tied to the facing bricks, with a nice coping stone to match whatever paving you have in the garden.

[job_bodger]

doh ! Whoops thought waterproof membrane and filter memebrane same thing.

Regarding the tying, there doesn't seem to be much information on the web how to use these. Is it that obvious when you get them ? I've seen the S.S ties but haven't figured out how they go round the brick

[Rich H]

I'm not a brickie but I've built plenty of garden walls and prefer a bit of belt and braces. There are three courses of bricks to one course of blocks. When you lay the second course of blocks you lay the butterfly ties in with the mortar. When you come to the 4th course of bricks, you mortar in the other end of the each tie.

LLL is the resident expert though. Just don't use cheap london bricks or he comes over all peculiar.

[lutonlagerlout]

LBCs are no good for retaining walls

f1 or f2 bricks ideally laid in english bond (1 course headers,followed by 1 course of stretchers)
flemish isnt quite as strong but is much more attractive

butterfly ties are out again rich ,we have to use these weird thin little ones now that dont feel strong at all

bring back the fish tails,i still got the scars!!

LLL :;):

[job_bodger]

Sounds like the English bond is the way forward then. I think I've got a decent price on some engineering brick so I think I'll use them. LL do I absolutely need to back fill ? I spoke to some builder at Jewson and he didn't seem to think so. People seem to disagree. Is Mr Jewson telling porkies ?

[lutonlagerlout]

always best to do jobs properly
that way they last
you dont want to be spending even more money in 15 years doing it again

i pass a wall in luton everyday built in LBCs it has already cracked after 3 years and i give it maybe 5 years tops before it will have to be rebuilt,if i remember i will take a photo and post it
cheers LLL

[job_bodger]

Can you recommend a material for tanking or waterproof membrane? Also can the backfill be all clean gravel or does bedding, sidefill backfill all have to be different.cheers

PS. I promise I won't use LBC's

[seanandruby]

Can you recommend a material for tanking or waterproof membrane? Also can the backfill be all clean gravel or does bedding, sidefill backfill all have to be different.cheers

bitumen primer coat painted on, then bituthene stuck to that.
clean gravel for drainage at back of wall ( as illustrated in picture ) what bedding? you should, hopefully, be building off a concrete foundation. also dont know what you mean with side fill. surely you wall will not have open sides unless the ground is "battered"

[job_bodger]

I saw a diagram of a retaining wall on the net. It had bedding which was the material the pipe laid upon (just above the concrete). Then it had sidefill around the pipe. Then it had backfill above the sidefill. Confused the sh*t of of me. Can't seem to find it again but doing a google comes up with these terms

[Rich H]

Gravel underneath, gravel to the sides, gravel on top, easy!

[job_bodger]

Pea gravel around the land drain ?

Do I need planning permission and should I inform the neighbour ?

My garden is totally fenced off.

[Rich H]

You don't need permission. The flow will be very minor - the purpose is to reduce the load on the wall and prevent the soil from being so wet that it is boggy and a long-term threat to the wall. Without seeing a layout it's hard to tell but presumably the wall has a return on one side of the conservatory or the other? Take the pipe down below ground into a small hidden soakaway somewhere sensible where the water can seep away. If you can route it to an existing soakaway all the better.

You're already doing far more than most DIYers and some 'professionals'! Most walls we take down or dig behind have nothing behind them but mud.

In the photo below is my old garden and my neighbour's, which I built (on the bleeding weekends) at the same time. The perforated pipe from the wall on the right can be seen on the left. Our two walls ended back to back with that pipe running between them, it was then sunk deep below his paving into his soakaway. Technically I should have done two, but the soakaway was big and the ground is free draining anyway. That was a few years ago and no problem with drainage, paving, walls or soil.

The finished job