Failed retaining wall - what to replace it with?

[barki]

Hi all

Pictures attached of a retaining wall that has failed in my garden.

I believe that lack of drainage has caused the failure. There is no drainage through the front of the wall or around the sides either. It seems to have failed above the first course of bricks, which themselves are held firmly by the paving.

It's 20m long.

I am planning to DIY replace it.

- When I take the old one apart, if I find the old footings to be in good condition, would you reuse them?

- I was planning on laying 80mm land drain pipe behind it, in 20mm gravel and wrap that in a permeable membrane. Due to the wall length, and the required fall along that length to get the water out either end, I was also going to install weep holes along the front, perhaps in the first above ground course. Maybe 15mm copper pipe perhaps. Any thoughts on that? Is it overkill to fit the land drain pipe in addition to weep holes?

- Is the wish bond design of the old wall a good plan? Even. Ring double skinned and with the header bond on alternate courses, it has still failed. Does it need piers, being 20m long?

- I wasn't intending on using a DPC, or even a DPM on the back of the wall, but googling I find mixed answers. Any thoughts?

- Finally, the wife is interested in timber solutions but I'm not keen...maybe less work, but we have on of those elsewhere in the garden which has also failed (both rotten and falling over - also without drainage).

Cheers & regards.

 

[Ivor Windybottom]

Timber's a complete waste of time. People are using it for all kinds of things at the moment, in gardens and houses, all will regret it. There's a reason you don't see many old timber buildings, they're not a new invention but only the stone ones still survive. With a few exceptions most old timber buildings and walls are now compost.

It doesn't look like the foundation has failed, it's bent rather than tipped, although check for yourself.

I'd say the design and bonding pattern is absolutely spot on. One issue is that the bricks are not sufficiently frost resistant. Groundwater has wetted them, it's frozen so popped them. A great shame, as it looks great.

I'd replace with something similar, possibly re-using the foundation, just with better bricks. Concrete bricks might be a good option, or clay engineering bricks.

It looks like there may be some substantial roots behind it, if so then perhaps it needs a thicker wall, e.g. a brick wall with a concrete core, or some woodland management.

More drainage is always better, as is damp-proofing. I built one from engineering brick AND painted the back of it with bitumen paint before infilling. No idea whether it would have been fine without, but it cvost £20, didn't take long and is invisible once buried. If you're going to put pipes through the wall then it needs to go somewhere, you may need drainage at the edge of the patio. Perhaps look at how that drains to where while you're at it.

 

[^woody^]

That damage is nothing to do with drainage, and everything to do with the wrong choice of brick.

If the timber effect is required, a vertical concrete slab on the back will retain the soil, and a timber whatever on the front will give the effect.

 

[barki]

Hi,

Thanks for your replies. The choice of brick is the same as the house, which is why they used it. I can see how frost has popped the textured faces off various bricks (but only the garden wall, not the house, which I thought was due to moisture), but I don't understand how the choice of brick has caused the wall to start tipping over?

Cheers, Tom

 

[^woody^]

Bricks on a house don't get the same exposure as bricks in a garden wall.

Those bricks do not have a sufficient frost rating - the damage has been caused by freezing, not moisture per-se.

 

[Ivor Windybottom]

I agree, there are two issues. The frost damage is due to it being wetter than the house, and also because it will be colder than the house walls due to the house emitting heat from the heating inside.

Requirements for a garden wall are more demanding than for a house, for these reasons.

The additional issue is that the wall is being tipped over. This is probably not related to the frost damage. Either it's inadequate and/or it's being pushed over by the jungle behind it. You need a thicker wall and/or to remove the rain forest.

 

[barki]

Interestingly, this is the brick datasheet which says F2 for frost rating durability.

Google reckons that's the best rating level..?

 

[^woody^]

There is no way those bricks are suitable for that use - they are soft clay, and that is what happens.

It's very common for some bricks despite a particular rating, to be unsuitable for a particular use.

So if you plan on using a clay brick again then you need to select one suitable for that use, in that location's exposure. You can save the time money and effort in any drainage and spend that on the wall materials instead. TBH, that vegetation is likely dealing with any excess ground moisture by absorbing it.

If the wall has been pushed forward then you need to determine if that was roots, soil heave or poor quality work, and allow to deal with that too

 

[barki]

Thanks again for your time in responding.

- On the vegetation, the picture makes it look more significant than it is. It's just annual weed growth, no big roots. I could strim it back to dust in half an hour but I've left it this year because the children have slow worms living in there...and go and check on them every day lol! In winter it's a barren slope.

- Regarding choosing a suitable clay brick, I suppose the difficulty is how to make that choice when I now know that even a brick that states it's frost resistant may not be.

- Play it safe and go for concrete bricks, perhaps?

P.S - The house is in a conservation area and so brick choice is a bit sensitive. That wall isn't visible from the road though so would perhaps get away with diverting from the current Ibstock Sahara choice. Still, any method that would yield a long lasting result using that same brick choice would still be the preferred option.

Cheers again

 

[Ivor Windybottom]

Check the specs for yourself, but these should last much longer than clay and look fairly similar...

Bricks and Blocks | House Bricks for Commercial Projects | Marshalls

Find concrete bricks and blocks from the concrete specialists at Marshalls. Including house bricks designed for a range of commercial and residential projects.

www.marshalls.co.uk

Scroll down for the colour range.

You can get samples, they usually send out a presentation board with slips (faces) glued on. The board background's black, I found I got a better impression by stuffing cardboard between the faces to simulate mortar pointing.

For the samples I got, I thought the colours were brighter than they looked online. After a few years of fading and moss they'll probably tone down.

Sometimes an obviouly different brick is better than a bad match.

You should check the details of the conservation area, there should be a document somewhere. They may list specific things they care about, I doubt that a back garden wall is covered.

 

[Ivor Windybottom]

Glencoe Stock Buff Facing Bricks

Glencoe Stock Buff/Cream Facing Bricks from Marshalls. Robust, strong and fully frost resistant from the beautiful bespoke collection.

www.marshalls.co.uk

 

[catlad]

Have you considered gabion baskets?

 

[Ivor Windybottom]

I bought from Brickhunter, and would highly recommend them. They will sell anything at normal full price but also do clearance bricks, usually leftovers from newbuild estates. They're extremely helpful and DIYer friendly, you won't get any bad attitude for not talking like a geezer!

These stand out to me, at a bargain price...

Batch 380

The Batch 380 brick is a pressed brick that is buff in colour with a light texture.

brickhunter.com

1780 available. You can order samples, delivery charges are normally reasonable. Think I paid about £300 for a full artic of 20 pallets, all unloaded very carefully by the driver using the crane on the truck.

If you phone them and ask they'll tell you the make and model info of each clearance brick that they don't state on their website.