|Posted on Wednesday, 10 May, 2006 - 03:18 pm: |
My garden retaining wall, in common with most of the retaining walls around the Tewkesbury Lodge estate, is in the process of giving in.
Most of the hill seems to be a solid clay deposit and most garden walls just aren't up to the job.
Does anyone have any good experience of good designs and/or contractors to replace damaged walls?
|Posted on Wednesday, 10 May, 2006 - 04:00 pm: |
Strictly speaking you should have an engineer design the wall. Catastrophic collapses are quite rare (mainly because people usually knock the walls down and rebuild them once they get too wonky) but do occur, and you may see a few walls where this is becoming more likely. The wall shouldn't actually move at all and therefore shouldn't need replacing if it is designed and built properly (and one brick thick won't do it).
Once designed, any decent general builder should be able to do it.
|Posted on Wednesday, 10 May, 2006 - 06:24 pm: |
The walls are very solid, widening to well over a foot at the base, and unlike some of the Victorian brick retaining walls, will not collapse. But at a certain lean they may be condemned by our friendly Council (shame they don't condemn any of the planning blights).
It will cost between 5 and 15k to rebuild, mainly due to the sheer time of actually demolishing it. Some neighbours have got his done on insurance, but it seems to be pot luck. They tend not be supporting walls, but if you were to lose them, the land would slip causing you to lose a supporting wall.
There are a variety of jobs done in the area. Some of the brick faced ones, very pretty when first done, have leached salts into the brickwork. Others haven't been properly drained - unlike the original ones that drained onto the street this is supposed to be against planning regs and there should be a properly engineered drain. But following council insisting on this I know of one house where draining was so efficient the garden started to dry up and resulted in subsidence.
Another wall is made of concrete blocks, waiting for this to fall down.
An alternative is to cut it down in size, below that of concern to the local authority, and/or reprofile the garden so there is less pressure on the wall. Lots of moving of soil.
As for builders, the most reputable and probably most expensive local one, who has done a lot of good quality work in the area, did a real shoddy job at our place (the subie had other things on his mind) and they did not make a decent job of making it good. Pot luck!
Try the UDB/posh estate residents association for further advice. One of the members was advocating a wooden wall (seriously), but not seen any taken forward.
Happy to give you more advice, particularly if you can give me some old bakelite door furniture in return
|Posted on Wednesday, 10 May, 2006 - 10:17 pm: |
Where is the Tewkesbury Lodge estate?
|Posted on Wednesday, 10 May, 2006 - 11:12 pm: |
Thanks for the helpful responses, my current favourite is a reinforced blockwork wall with rendering.
Seeformiles - the TL estate is the bit around the top of the Horniman - Westwood Park, Horniman Drive, Tewkesbury Av, Ringmore Rise, etc.
|Posted on Wednesday, 10 May, 2006 - 11:16 pm: |
Not a bad choice Les. Engineering brick or reinforced concrete are better in some ways but doubtless significantly costlier.
Just don't have the render painted white or even on the Hill some passing imbecile will probably feel compelled to autograph it!
|Posted on Wednesday, 10 May, 2006 - 11:31 pm: |
Getting an engineer to design the wall is a good idea- one of the reasons for these problems occuring is the lack of adequate drainage for the soil being retained which means the water pressure and weight just builds up and pushes against the structure. A lack of foundations is also a contributory factor, as is construction in unsuitable materials, ie concrete, which does not resist pressure very well unless reinforced. Reinforced concrete block with render is probably the best solution.
I have seen walls put up recently in brick with topsoil subsequently stacked up against it- asking for trouble.
There was some good work done recently in Woodcombe Crescent- either no 39 or 41. We got a quote from the same firm but it was way out of our league, but the standard seemed very good.
|Posted on Thursday, 11 May, 2006 - 08:03 am: |
Try a firm called Abbey Pynford. They will engineer a solution that will not move.
|Posted on Thursday, 11 May, 2006 - 09:48 am: |
Roz is on the money. The other factor is that without much of a base / foundation the whole wall will start to rotate and tilt outwards. It is quite correct that wall built like a normal graden wall with soil banked up behind it is just an accident waiting to happen.
|Posted on Thursday, 11 May, 2006 - 09:57 am: |
That's why you need a firm like Abbey Pynford. They will probably recommend a piled foundation tied to a steel-reinforced concrete wall, which could be rendered and painted. Sounds expensive I know, but you may be pleasantly surprised - and it would last forever!
|Posted on Thursday, 11 May, 2006 - 11:18 am: |
I imagine they will recommend a piled foundaton, because they are a piling firm.
|Posted on Thursday, 11 May, 2006 - 12:20 pm: |
I'm a little bit lost here. I've watched walls knocked down and then be replaced in the area over the last 5 years. Only one house has used blocks, and they have moved already. Perhaps the Abbey Pynford solution is best, but I would advise against replacement seeing how solid the orginal ones were, even if they have moved (rotated/tilted). Of course it depends on your position, depth of soil, drop, length of garden etc. As orginally suggested suggest you talk to the residents assoication, and also walk up roads such at Tewkesbury Avenue and knock on a few doors.
The originals were also reinforced but not to the same standards as being talked about above.
Tewkesbury Lodge Estage is also known locally at UDB but now a local Estate Agents has coined it 'Horniman Heights'. How quaint. In future I hope we can just name it by the school catchment area so we can be known as the Habberdashers area of Forest Hill. Ho ho.
|Posted on Thursday, 11 May, 2006 - 12:50 pm: |
BD, the rotation of the wall is itself a sign of engineering failure. The wall ought not to move appreciably. It is no good the wall being solid in itself if it rotates and falls over as one lump. This is no better really that a big crack appearing at the base - the other way it could fail. (Third possibility is sliding). We ought not to be thinking along the lines of "the brick wall lasted 30 years, until it ended up at a 60 degree angle". In that situation it is too unpredictable and could be dangerous. You can't really predict whether it will keep tilting over a degree a year or whether it might just collapse completely all of a sudden.
|Posted on Thursday, 11 May, 2006 - 12:50 pm: |
...and is being in the Haberdasher catchment area wishful thinking? We aren't, are we?
|Posted on Thursday, 11 May, 2006 - 01:12 pm: |
Don't think that piles are necessary. Most of the walls that have failed around me have cracked and pivoted forwards at the base. The foundation below is stable. Mine is like this.
Most of the houses are also on spread footings (basically trenches part filled with concrete) and are also stable.
This is a feature of our lovely clay hill - the clay is reasonably strong, but also generates large active pressures on walls as it swells and contracts with the seasons.
|Posted on Thursday, 11 May, 2006 - 01:53 pm: |
The houses aren't being pushed from one side though, just resting on the ground.
|Posted on Thursday, 11 May, 2006 - 05:10 pm: |
Les - The idea is that the wall and the piles would be effectively one unit, which is bound by steel reinforcement. Any lateral forces against the wall above ground would be counteracted by piles at whatever depth is deemed necessary given the local conditions.
|Posted on Thursday, 11 May, 2006 - 05:41 pm: |
Miaow HT! 'Habberdashers catchment' was from an estate agent ad in Living South (magazine for the posh part of SE23 for those of you from the wrong side of the tracks). It amused me. After 2 years of posting tongue in cheek I am pleased that I can still catch me out. And my original reason for getting into this was to get a response out of you.
The discussion is getting rather technical. At what point is the lean so extreme, and the footing so poor, that the walls collapse? It must have to be pretty extreme before the weight of the soil takes over.
|Posted on Thursday, 11 May, 2006 - 05:59 pm: |
BD, you are a tinker. Apparently Haberdashers will take young UBD-ers / Tewkesburians / Hornimen.
Your original reason for getting into what? This thread, or did I inspire you to bring your magic to se23.com?!
It is indeed getting technical; who would have thought that such widespread knowledge and expertise in civil engineering matters was to be found in FH.
As for when the wall will eventually keel over, I don't know. If it's cracked at the bottom and (casting my mind back to O-Level Physics) leaning more than about half its thickness it must be well on the way though.
|Posted on Friday, 12 May, 2006 - 12:36 am: |
With Haberdashers now in the North and South of Lewisham the entire borough is officially posh. If you are into walls..try the web cam links on these two pages...
|Posted on Friday, 12 May, 2006 - 09:29 am: |
Well, Living South must have got that message too, because we receive the posh mag on this side of the tracks as well.
|Posted on Friday, 12 May, 2006 - 02:28 pm: |
I stand corrected as the Haberdashers' catchment area is three miles. We are about 2 - 2.5 miles away. But worried that the wrong side of the tracks may find out. But the whole thing is actually a load of bull walks.
|Posted on Friday, 12 May, 2006 - 05:22 pm: |
A free standing wall with a crack at the bottom will fall over, if its centre of gravity normally half way up, in the middle), is outside its plan area at the base. Unless there's something tying it back...
Agree with Hilltop - Brunel would be proud of us.
|Posted on Friday, 12 May, 2006 - 05:50 pm: |
They taper upwards so the centre of gravity is lower. But look forward to hearing of your progress Les, even if you have butted into my love-in with Hilltop
|Posted on Friday, 12 May, 2006 - 11:56 pm: |
OK Baggy, will let you carry on with HTG, and update once the mortar has stiffened, so to speak.