Cast iron pipes, wooden plugs rotted away - best way to fix ?

[SimonH2]

A bit borderline between here and plumbing section, but this part of the question is more building than plumbing I think ...

c1940s ex council house in red brick and rendered.
Been working around various jobs (and painting as I go), and got around to the wall where the soil stack is.
When built, they just nailed through the ears of the cast pipe sections into lumps of wood - and in the 70-something years it's been up, the wood has rotted somewhat. The greywater hopper and downpipe is easy - that's light and easily removed and re-installed - the soil stack is a different matter and I really don't want to move it, but it's clear it's no longer well supported.

I was thinking of pulling the nails out (one at a time, starting with the loosest - don't want it falling), somehow removing what's left of the wood, somehow piping in some cement mix, and pushing in some studding. That should leave me with some studding fixed into the brickwork and I can just tighten nuts onto the studding once it's all set (carefully so as not to move the pipework or break the ears off).

There's about ¼" to ½" gap between the ears and the wall (the original wooden plugs were left proud of the rendering), and the nail hole through the ears, so quite limited accessibility.
Any thoughts on how to remove the remains of the wood and get the cement in ?
Any other suggestions ?

NB - I'd like to keep the cast pipework. In part because I think it suits the house better than plastic, and partly because it's a lot quieter - we can hear when the neighbours flush and it rattles down their plastic stack

 

[Tigercubrider]

I'd do as you suggest, maybe use a quick set cement? A short offcut of pipe can act as a spacer
Digging the wood out is hard to say. A hand tool might be easiest

 

[bernardgreen]

Studding held in place in the wall using chemical anchor resin such as THIS will give a permanent fix.

Snags are that the applicator gun is expensive and the resin hardens very quickly which means you have to work fast to get the studdung into the resin filled hole.

The disposable nozzles mix the two part resin as it is forced through the nozzle and if left for a few minutes the mixed resin in the nozzle will harden and the nozzle has be replaced.

I would do one hole ( or maybe two adjacent holes ) at a time and use a new nozzle each time. Do NOT put resiin into a hole until you are ready to immediate push the studding into the hole. Wiping resin onto the studding to fill the threads will ensure the studding is gripped by the resin.

 

[SimonH2]

I'd thought about the resin fixings, but wondered if they'd be suitable for hole filling. I have used it before - but only for fixing studs (24mm for a building frame) into closely sized holes.
I think I'll have a go at raking out a hole first and see what sort of size it is once past the render.

 

[bernardgreen]

I have used resin for fixing studding in stone walls and while it can take a lot of resin to fill the voids it does the job.

When my roof was being re-thatched the thatchers were having problems anchoring spikes into the tops of the stone walls ( rubble and mortar ). I suggested resin and they found it ideal ( and wished they had known about it before )

 

[SimonH2]

Well I made a start and took the hopper and top section of pipe off one of the drains. Getting the wood out was fairly easy with the aid of a drill. Now I can see that they have used wooden wedges driven into the gaps in the brickwork, then round spacers to hold the pipe away from the wall. Then they've rendered the wall working around the pipes.
So getting all the old wood out leaves something of a void behind the rendering.
I've decided to try cementing a stud in first - this pipe is lightweight and easy to deal with if it doesn't work well. I'm planning to put a nut on the stud to increase the hold (might need hammering flat a bit to fit the gap) - though in the past I've tried to unscrew some studding that was concreted in and it was "very solid" indeed.
While I was out buying some studding, picked up a long drill bit - should be able to work through the hole in the ear (of the larger fixed pipes) and reduce the wood to small stuff that will blow out with an air line. To get the cement in, I'm thing that I can cut a little over half a bit of pipe to sit between ear and wall below the hole. Then I can tip the cement over the top of the ear, the bit of pipe will hold it, and I can ram it into the wall with a stick through the ear hole.
The joys of house maintenance

Edit: oh yes, stainless steel studding, like other jobs I've been doing - I intend it to outlast our time in this house and neither of us is thinking sbout moving again

 

[SimonH2]

Just an update ...

Did the drainpipe with cement as it was easy to remove in order to give access to pack the cement in round the stud.
Did the soil stack with resin. The more I looked at it, the more I could see that I wasn't going to get cement in properly with the space available.
Now I'm just left with what to do about spacers. For the soil stack I'm toying with a stiff cement mix and just pack it in behind the lugs. Without knocking a lump of render off (or disturbing the stack), I can't see how I'd get anything else in.

I had another job for resin fixing so did that while I had tube open. And as a hint, cooling the resing pack down increases working time - according to the table on the side of the tubes I used, from about 5min at ambient to about 20min at 5°C.

 

[oldbutnotdead]

Some bits of hardwood would do for the spacers (use a holesaw to make round bits if you like then drill the centre and cut a channel so you can slip them over the studs). Or get a lump of Unistrut and cut bits of that to length- not as pretty but more robust probably. Real posh would be get a length of nylon bar about 40mm diameter (Ebay is your friend), again cut to length and drill and slit to fit over the studs

 

[Harry Bloomfield]

Once the wood plugs are out (I would use a drill bit to get much of the plug out), you can fill the holes with car body filler and a threaded rod cut to length. Car body filler will set up solid in 30 minutes, instead of the 24 hours cement needs to set.

 

[SimonH2]

Already got the studs sorted, cement for the drainpipe that's easily removable, resin for the soil stack that isn't.
For the drainpipe, spacers aren't too much of a problem as I can remove the pipe to fit them. The issue is with the soil stack.
There's now a hole in the render behind the fixing lugs, and a limited gap to push things into. If I took the pipe off then there'd be no problem - but I'm not disturbing the soil stack ! So whatever I use needs to be flexible so it can be pushed in through the small gap between lug and surface of render, but which will set so I can tighten the nut down on the stud and things will be rigidly fixed.
When they built the place, it was easy - they put the bobbins in, nailed the pipes in place, then rendered round them. Bit harder now everything is in place.

 

[oldbutnotdead]

Body filler as suggested, sleeve the studding with a bit of pvc tape or thin tube and wodge it in- it'll go off quick and you can sand it smooth later.

 

[Harry Bloomfield]

There's now a hole in the render behind the fixing lugs, and a limited gap to push things into.

You need some sort of applicator, where you can squirt the body filler through a tube into the back of the hole to fill it, then push your stud in quick.

Thinking aloud - An empty silicon sealant cartridge with the nozzle and the cheap gun. Clean out the remnants of sealant, fill with the body filler, then its nozzle might go through the hole in the lugs. You would have to have everything prepared and be quick because it goes off very quickly.

Alternative idea - An icing bag, as used for making cakes, with a bit of tube to extend to the back of the hole. Never used one, don't know how suitable it might be, but mixed body filler is quite fluid.

 

[SimonH2]

READ AGAIN
the studs are already fixed in the wall

It's now a question of filling the gap between the face of the cement/resin used to fix each stud and the back of the lug the stud fixes. This isn't too much of a problem for the drainpioe as I can remove those, flatten up the fac with cement, and slip a spacer on the stud.
But the soil stack is fixed (and with the joints all securely sealed) and I have no intension of moving it. So I have to use something that is flexible enough to put through the available gap, but stiff enough to be self supporting (ie not run out of the gap at the bottom), and sets hard so I can do up the nuts and fix the pipes properly again. At the moment it's going to be either a stiff cement mortar mix, or perhaps the car filler suggested oldbutnotdead - perhaps the type that's filled with glass fibre which would make it nice and rigid once set (I once repaired a door at the office with that !)

 

[bernardgreen]

Could you create a mould from cardboard shaped around the lugs and then fill the mould with resin.

The stud would need to be sleeved to prevent resin getting to the threads where the nuts would be fitted

 

[SimonH2]

I might try, but it's a fiddly location to work in. Not to mention, the resin is "a bit runny" so I might struggle to keep it in.