Retaining wall extension

[mymini86]

Hello, everyone. I am looking at extend my retaining wall at the bottom of my back garden so I can level it off. Could someone tell me if I can simply build up the existing wall or does it need some sort of reinforcement for the extra load? If so, What is the best method?

I am planning to build a single garage/workshop in the near future as shown in the 2nd pic, will the wall be strong enough? The red line in 2nd pic shows the existing retaining/boundary wall.

The other side of the wall is an overgrown jungle, no man's land and no public access.

Thanks in advance.

 

[mike os]

That wall is not in tat good a condition tbh.... could do with some repointing at least.

I would not be happy adding 75% to the height of an existing wall without knowing exactly how it is built. too much risk of overturning or collapse.

personally .. as long as it cant be seen from the bottom of the slope ... I would use gabions personally.. ( and insert drains) but only if I were happy the exiting structure would be OK with the additional load.

what is below the wall? remember you are responsible if it collapses

 

[Wendelspanswick]

So if I get you right you want to build up the existing wall by another 1.5m and then fill with soil to level the garden, and then sometime in the future build on the levelled garden?

 

[mike os]

missed that bit.. the founds for the garage would need to be piles to below the shear line for the retaining wall.... ie about 3-4m at a guess

 

[cumbriasteve]

If the present wall is 50 years old and only a double brick wall it has done fairly well so far and the mortar is bound to be at a stage where it is not at it's best, which looking at the lower parts would suggest the same.

I certainly don't think it is a simple case of extending the wall to suit your requirements without other means of reinforcement.

I have seen a similar job done where the builder added a buttress about every 3 to 4 metres to the rear of the wall, not sure if that is an approved method or was just his own idea.

 

[captain-destructo]

here's a fiew ideas

 

[Kent]

too much adaptation of unknown existing things is not good. Decide exactly what you want and then build it for purpose. It looks like water is already coming through that wall which will be weakening it, you don't know anything of the footing or even how thick the wall might be at its base - everything is a wild guess at present

 

[SmartWerks]

Quicker and cheaper to knock down and start again, and a lot of old buildings were built straight on the ground with no footings. Building inspector wouldnt sign it off that's for sure. Reinforcing and pile driving would cost more than building from scratch. Downside is asthetics if you want it to blend in as rendering doesn't come cheap.

 

[mymini86]

Thanks Folks! Appreciate all your input! I didn't expect to get this many replies in only a few hours!

The scale is a bit wrong in this drawing, but you get the idea.

As it is the boundary wall, that means the buttress idea is a bit difficult even it is a jungle atm and as far as I know it is no man's land, but I am sure if I start to build the council's planning dept will be here in no time.

Garage/workshop is definitely the goal, gardening is just boring :0(

I think @mike os might just hit the nail right on the head, by using gabions hopefully it can transfer the load on the wall downwards, and perforated drain at the bottom to release hydrostatic pressure.

Thus less pressure on the wall = I can build it higher?!

Is there any other method out there?

 

[Spark plug]

Investigate the no mans land claim it and build a bigger workshop

 

[mike os]

3.5m is quite a high retaining wall. Not something I would want to design myself, despite having been in building for 30 years....really wants a structural engineers input

Rebuild you are looking the wrong side of £1000 a metre

 

[RBDIVE]

I agree with Mike os, this wall really needs to be designed by a structural engineer. 3.5m high is going outside the range of standard garden retaining walls. i would not recomend that you build off the existing. We would to know what soil type and the type of trees the distance of these trees and their current height, incase they impose any effect.

 

[Kent]

I missed the bit about it being a boundary wall ! You need to read and understand /comply with the boundary wall act for starters. You really are into a can of worms with this one on so many regards. Could you leave it up and leave a gap then build exactly what is required, it will help with water penetration and all the other issues

 

[mart]

There is a bit here on retaining walls that I was studying when I was working on mine.
http://www.selfbuildselfhelp.com/Advice/DoingStuff/RetainingWalls.htm

 

[Wendelspanswick]

There is a bit here on retaining walls that I was studying when I was working on mine.
http://www.selfbuildselfhelp.com/Advice/DoingStuff/RetainingWalls.htm

That's the same link as I used to help me with mine!

 

[mart]

That's the same link as I used to help me with mine!

Too minds alike

 

[captain-destructo]

Too minds alike

AND ..........Ill stop myself there