Bowed Garden retaining wall - HELP !

[shankly9]

Hi - newbie here after some advice please.....

We purchased a bungalow couple of years ago which sits on a hill, the garden to the property is about 7ft down accessed by steps, the garden slopes downwards to a retaining wall at the bottom.

The wall in question I have a problem with is the one at the top of the garden, in theory what the property sits onto ( there is actually a concrete pathway between property and wall in question, so it doesn't actually sit on top of it )

the wall is constructed from blocks and we've noticed this winter that it has bowed out, which has also caused the concrete above to drop and crack ( we think ) quiet badly, a couple of inches in some places.

The wall is 10m long and about 7ft high, we can only see the exposed side, so don't know if its single or double (hoping its double but doubting after renovation of inside).

To compound issues, we had a cracked drain which we didn't notice and all the water was seeping down into the garden through that wall which we think has been the route of the problem in the main, the drains have now been fixed, but we are left with a severely bowed block wall and dropped concrete etc above it.

I don't think we can take the wall down, I am worried that if we do, the rear of the property may go with it ! as that wall is retaining all the foundations etc etc as its only 3ft away from the external wall of bungalow.

SO.... what can we do ?

Could we have another wall with pillars built in front of existing and tie it in to support it ? Would this offer the required support etc to stop it from going anywhere ? Or just be a waste of money ?

How far away from the existing wall should a new wall be built ? should it be backed filled, if so with what ?

Do you guys have any experience of this ? Or can maybe offer some other solution to our problem ?

We have a tight budget, house is actually for sale after renovating it internally, so funds are low, but we still want it right for the next owner and our own piece of mind etc.

Any suggestions please ??
Any help advice greatly received......

 

[freddiemercurystwin]

Some photos would help, a beast of that magnitude will need structural engineers solution/design rather than some guesswork from a forum. Trouble is its not just inconvenient if it ever went, its a potential killer.

7ft bowing retaining walls and cheap are not really two things that can be banded together.

 

[shankly9]

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• shankly9
• 16 Apr 2015
• 1

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• shankly9
• 16 Apr 2015
• 1

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• shankly9
• 16 Apr 2015
• 1

Not sure if they are any help ?

 

[theprinceofdarkness]

I would think that the foundations of the house will go down the seven foot into solid ground. Confirm this by looking at your neighbours gardens and or looking under the floor boards at the back of your house. I do not believe any one would build a shallow foundation house next to a seven drop*. Likewise I do not believe that some one would dig out and cart away the volume of soil to transform a sloping garden into a level one by removing the seven foot.
So the chances are that the wall and its earth is just there to support the concrete path outside the kitchen door.
Depending on the height of your "cellar", if its there and of considerable height, I would use a land anchor from the front of the hoouse through the wall to a large strap on its front and fill the depressions in the path with concrete. If your "cellar" is of no height at all, then the only course would be to buttress the wall to keep it and the house from slipping downhill.
FWIW I know of a bungalow, built like yours on a steep hill, until it was modified, it looked absolutely normal. However some one had dug into the hill side and put a door way int the rear underground wall. The resulting cellar was HUGE!! with supporting walls under the walls in the house, so it had the same plan and 7'+ headroom at the back tapering to 5'+ at the front.
Frank

 

[shankly9]

Hi Frank

thanks for your comments.

There isn't a cellar at the property at all.

I am tending to agree with you that the foundations would go a lot deeper than I am thinking, and the wall is really to keep the "top" part of the garden where it is.

My neighbours bungalow is about 5ft lower down than ours maybe a lot more. I am hoping to be able to build a new wall in front of the existing just to add some extra security there and then re-concrete the top and level it all up, maybe when that is broken up, it may reveal other problems for me, or maybe if I am very lucky it won't, the place has been there 100 years already so I am sure its not about to go tomorrow, but it doesn't look great and is concerning us to the severity of the damage the cracked drain has done.

Note to self..... never buy a property on a hillside again..... more problems than they are worth !

 

[theprinceofdarkness]

I wonder if there are no bleed holes in the wall? This would have caused your problem with the leaky drain, the resulting water backing up behind the wall. If there are not any, put some in tomorrow, say 16mm diam every 600mm at the lowest point of the wall you can get to- just above the lawn?
As you have found out building an earth retaining wall is a proper design project for a structural engineer, else the wall will just fall over. It will also need very substantial foundations. Which will also undermine the existing wall while the hole is dug.
All earth has a natural slope. If you cut out a large section, a large triangular cross section of the earth wants to slip forward, because with a vertical cut its unstable unless its rock or chalk. If the earth is wet it will have a much lower angle so the triangle gets longer. So suppose the angle for your soil type is 15 degrees, the wall will be supporting a wedge of soil, seven foot high with an angle of 15 degrees which I make out to be almost 26 feet long!! However it is likely that the house foundations will be supporting most of this wedge, so your wall must support a block sitting on a wedge the width of the path which could be 6 feet high, so its quite a few cubic yards of soil at .8 ton per cubic yard.
Rather a long winded of underlining the requirement for substantial foundations for the earth retaining structure. I would go for three buttresses each 9" wide (hollow blocks) and 18" deep, with a piece of 16mm reinforcing rod that runs up the cavity closest to the wall. The bottom end of the rebar being bent at right angles and buried in a strip foundation, say 2 foot wide one foot deep and eight foot long buried at least 3 feet underground, at right angles to the wall. So its a gigantic L bracket. Oh yes and the holes in the blocks filled with concrete as they are built up. Cut the top one of at 45 degrees and fit some tiles to finish it off.
Because of the relative narrow foundation trench it should not undermine the existing wall too much.
Frank