Remove rubble from cavity

[Why Not Indeed]

Back wall of my house is always cold and tends to get mouldy at the bottom. It's built in to a slope somewhat, the ground level outside is about 5-600mm higher than inside. Pile on the left has come out of the cavity. The DPM is right at the level of the flags, one of which I have taken up:

I've taken out a window board to see what's going on and it's got quite a lot of rubble in [picture isn't too clear but that's about 300mm deep].
That grey stuff with a timber block on it is clear plastic sheeting and it runs down to floor level behind the plasterboard. This is presumably an attempt by a previous owner to fix a damp problem.

A few questions....
- Is there some tool/technique the pro's use for removing rubble from cavities? Tried a 'grabber', it takes 2-3 attempts for each item, painfully slow. Had my son doing this for 5p an item but it was more work supervising him than doing it myself [and was looking like bankrupting me]. I've got a 48" wrecking bar and a Henry. That's been a bit quicker, smash everything until it's small enough for Henry to suck up. Still damn tedious work though. I need a rock-crushing attachment for the Henry.

- How about that earth directly against the exterior leaf? Should there be a DPM between that and the wall, or what? Retrofitting that is going to be pretty tedious and even more laborious.

- The highest point of the rubble in that picture actually seems to be piled on a brick that's been mortared in place, in the cavity. Is this some early form of cavity tie? House was built in the mid 1960s.

 

[JohnD]

I used a canister vac with a steel tube. You can ram it into the rubble and it will either break it into smaller bits it can suck out, or it will hold onto larger pieces and you can withdraw the tube and pluck them off the end.

If I was doing it as a business I might assemble a core drill on multiple extensions. I don't think an impact drill will work when the drill and extensions weigh more than the machine. I have some long SDS+ drills and chisels about 30" long and a very heavy SDS+ tool that was cheap at Screwfix. It cut up a demolished wall in next to no time. Working downwards the weight is not a problem.

You can also fabricate a long-handled rake.

The exterior leaf should be isolated from the ground with a trench or by lowering the ground level.

 

[JohnD]

Notoriously cheap and heavy, but it has a 2 year guarantee and you should get your moneys worth out of it quicker than that. The version with accessory kit is very good value.

Titan TTB278SDS 6.3kg Electric SDS Plus Drill & 9 Piece Accessory Kit 230-240V - Screwfix

Order online at Screwfix.com. Supplied with a 9-piece accessory kit, this Titan TTB278SDS SDS Plus drill comes complete with everything you need to put its impressive power straight to work. The accessory kit contains five drill bits, ranging from 6mm-14mm, and two chisels in flat and point...

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[^woody^]

It's technique. First create a vertical edge in the debris, then use the bar as a lever. Debris in cavities is invariably loose and poorly bonded, so breaks easily this way. Then vacuum.

The alternative is coring holes every four bricks - that's the name of them, not a process!

 

[jeds]

You could hire a really good quality vac, but that's only going to be any good for the accessible section below the window. Is the issue isolated to that small area or does it extend further along the wall? If so you will need to remove bricks at intervals - every third or fourth, or two bricks with 3 or 4 between? Rubble is normally then raked out with a length of rebar with a hook bent on the end. It also looks like you will need to reduce the ground level as well.

 

[Why Not Indeed]

It's difficult to see the extent of the problem further away from the access I have, but under this window does seem to be deeper. We've been mulling over the idea of putting another window in where I can't currently get to the rubble so this might be another entry in the "for" column.

I've actually made fairly good progress with Henry + wrecking bar. About 4-5 Henry's worth and I can see the footings now.

As regards lowering the ground level - I think this is a non-starter. The whole site is sloping. If you stand at the end of the garden, the peak of the roof is pretty much head-height and the garden is 20m long, so that gives an idea of how steep it is. Lowering the ground level would mean adding a 600mm ladder to the bottom of a set of steps that give access to the rest of the garden

So what about decoupling the ground from the outer leaf of brickwork?
- Remove flags, dig out a 600mm trench, sheet of DPM against newly-exposed brickwork, refill, replace flags
- As above but put an Aco drain or similar on top [would require trimming the flags]
- As above but instead of backfilling with earth, some kind of insulation to thermally decouple it as well

 

[JohnD]

The ground against the wall needs to be about two bricks below the dpc to prevent water splash.

Preferably these bricks should be exposed to the air so they can dry out by evaporation.

To reduce the risk of falling into an open trench you can backfill with large pebbles or cobbles. These are free draining and do not support so-called rising damp because the gaps between them are too large and irregular to provide capillarity. You have to prevent mud, soil or gravel washing into the trench and filling these gaps. Landscape fabric will form a barrier and/or you can use paving slabs on edge. Sometimes a low brick wall is used. It must not rise above the DPC or the ground. Sooner or later some idiot will fill it with soil and use it as a flowerbed.

If you can lead the trench downhill past the house so it can act as a French Drain to reduce water in the ground, so much the better.

To reduce the cost of decorative pebbles, you can use them as the top layer and use clean broken stone, or brick or concrete pieces (no fine material) below.

Minimum size of a hen's egg, preferably bigger.

Flints and pebbles are non-absorbent which is better. Round pebbles maintain the gaps better.