clay lump wall repairs.

[robgil]

after stripping off all the cement render from my clay lump lean to i noticed one of the walls has very bad water damage at the foot of the wall. the first two courses of clay lump has turned to sandy rubble. the wall is leaning badly.
the problem with this wall is it is the exterior wall however there is a block extension built beside it.

i need to replace the clay lump blocks that have rotted but can i do it in situ or would it be best to dismantle the wall then re-build it?



this is the wall,

this is it in the flesh.

that water butt in the last pgoto was over flowing for two years and the water soaked the base of the wall , i suppose the cement render didn't help either.
so , do i take it down or can it be fixed in situ? either way i am not too bothered but easiest is always best.

 

[Flyfisher]

I can't really help with the wall, but I would just mention the importance of having proper overflows and soakaways for water butts. It's quite surprising how quickly they will fill up, and therefore overflow, when it rains. We have one that will fill up within about 10 minutes in average rain. Useful as they are, they should never be regarded as a method for disposing of rainwater, they merely collect a small portion of it and most of the water needs proper disposal just like any other downpipe.

 

[Jon Maine]

I would imagine if you took the same principle to underpinning and took out a small section at a time built it back in, let it cure and settle then do the next section the same way you should be fine. Probably a little more fiddly than a rebuild but less disruption.

 

[robgil]

because it is clay lump if i take small sections out wont it all come down? the wall is only around 6 foot long and i think the only thing holding bit together is the cement render on the other side.
is there any way to in stall some sort of temporary lintel while i take the rotten blocks out from the base? there is a red brick plinth under this wall and from what i can gather it needs attention also.

edit - to show you the severity of the rot , the second picture down there is a hole in the wall just above the cement render , i can put my hand in there and feel the inside of the render on the other side. :shock: the blocks are the consistency of sandy rubble and just slide away when i pull more render off.

 

[Stephen]

Because the extension floor is higher there will presumably always be the risk of lateral water penetration to the base of the clay lump wall. I would therefore suggest that it would be no good simply replacing clay lump with clay lump. You should consider heightening the plinth wall under the clay lump. Whether you do this using bricks or blocks is for you to consider.

As already suggested you should deal with it carefully as if underpinning. If you only take out small sections at a time the areas above may hold up, but provide props to prevent the wall collapsing on you as you work.

If it is so bad that you cannot even do this it may be that the wall is beyond saving.

Stephen

 

[christianb]

Is there a stone plinth there at all?? It's the old saying about a good hat and a good pair of boots.

I'd concur with Stephen, here. You might find, though, that the wall holds up fairly well when you start alterations. After all, it's possible to remove a lintel and find that the cob stays put without the need for acro-props. But sometimes not.

 

[Jon Maine]

Thats a fair point Stephen has raised, I would suggest that you did exactly that and built the plinth up a bit higher.

You could do this by simply removing a small hole laying a few bricks, letting go off and then do another section, I would consider doing the wall in 500mm long sections in a sequence of 3, 1, 4, 2. Then leave each section to cure until the mortar has reached full strength. Of course you can pack the last section with roofing slate and mortar.

You will have to assess if this is a suitable way forwards but it should be possible to build in sections leaving the ends toothed for the next to bond to it or square with some ss ties stuck out. Doing such small sections may enable you to keep propping to a minimum too. However you do need to assess whether the wall is stable enough to stand up with 1/4 of its support removed which is highly likely but not able for me to assess without seeing it.

By doing this it would mean that it was a minimal intervention repair thus leaving historic fabric above untouched which is good practice.

 

[robgil]

cheers guys. i also think lifting the plinth up to the exterior ground level would be a good idea. would i need to use any kind of dpc if i used brick? i kn ow the traditional way to do this kind of plinth would be to use flint rubble and i can still see the flint rubble plinth in a lot of the wall , why this particular section is brick i have no idea.
i am pretty sure the primary cause of the damage was the overflowing water butt but how much damage was caused by the elevated extension ground level i dont know.
doing it in small sections is a good idea but i am really scared that the wall isnt safe , at the base where you can see the remaining cement render the wall is around half if not less than its original depth. this damage may well be older than the render as the render is deeper here as if to fill out the deteriorated blocks. whats left is nothing more than damp sand , its as if the clay binding within the block has been washed away.
the other thing that scares me is the wall is leaning , so if i am working at the base i will have a wall leaning out above me. i can prop this with some 2x4 fixed at the floor and leaning into the wall and some scaffold across the wall? but it still scares the bejesus out of me.

 

[Jon Maine]

Nothing like a little undermining to make a certain part of your anatomy twitch :shock: :shock:

 

[MdB]

Robgil's complete picture:
http://periodproperty.co.uk/forum/download/file.php?id=1445

(I'm a complete non expert in this but I would suggest that ideally you should use a longer piece of wood so as to keep the angle closer to 30 degrees from the horizontal rather than 45 degrees.)

 

[Stephen]

I would suggest a piece of board (e.g. stirling board or shuttering board) to cover as much of the wall as possible and then have two raking props to each end, one towards the top and one towards the bottom. A piece of timber across the feet to hold the feet secure (as you have shown). This would then support a larger area of wall and not just the top section (as would happen if you use a plank as you have shown). It is all very well propping the top to stop it falling, but in this instance you really want almost whole wall support to stop it slumping.

Stephen

 

[robgil]

thanks guys, you are quite right Stephen , a board would be much better than a plank.
the other issue i have is what is above this wall , as you can see from the outside photo there is a wall above this one however from the other side it doesn't look like it is double skinned ,what i mean is i think the extension wall is built ontop of this clay lump wall. i think, judging by the way the flat roof of the extension falls to the rear of the house that the rafters supporting its roof will run from front to back rather than from side to side , should i support both ceilings as well?
another thing is i may be replacing the kitchen roof soon so should i wait until i have the roof off, or is it better to do this under cover do you think?

 

[Jon Maine]

I would say that the weight of the roof would actually stabalise the top of the wall in position. I see no real need to prop it.

 

[robgil]

cheers fella , still not looking forward to this job , hard hat and boots for this i reckon , and a spare pair of trousers.