Wanted - an old builder

[Tony]

I have an old house whose walls are of irregular, random shale, set in a soft lime mortar which can be picked out with the fingers. Fixing anything to such walls can usually only be reliably done by using skewed timber wedges hammered into the mortar, then nailing into these. A nuisance, but not too bad for one or two battens, but I really can't see how to achieve a flat surface for fixing sheet materials, when, maybe, a dozen or more plugs have to present a flat surface to the sheet.

Using 3 or more battens, in lieu, presents exactly the same problem. Surely the solution is a bit more sophisticated than stretching a string between the outer battens then hammering harder on those between to make them align correctly.

As this is a task which crops up from time to time I'm hoping that some older tradesmen might offer a few pointers.

Tony.

[MrCheerful]

Well you could use some strong grip fill stuff and glue them on, this would allow you to level them by squidging the high ones further in. To save on the bits of wood in holes you could use one of the resin injection kits like this one from screwfix: 51021

But what about the adjustable screws that screwfix sell, they are specifically recommended for your job. Have a look at:

are several different sizes available

mrcheerful

[The Natural Philosopher]

The way I would approah this - having seen some remarkably good carpenters tackle just such a problem - is to built a flat true and square frame, and apply it to the wall, and then fake up whatever suppoorts are needed at its edges.

If you juts want to e.g. slap up a piece of flat MDF, may I suggest that you first paint the wall with a thin epoxy resin and then when that has gone off and stabilised the loose stuff, use some large gobs of car body filler as pads to hold it in place.

[jacob]

The old way is to knock in wooden plugs on the line of the vertical battens or studs which will then hold the sheet. The trick is to make them too long and then to trim them back with a plumbline vertically, or with straight edge horizontally or vertically, or by eye - one person eying along whilst the other makes a mark. The trick with wooden plugs and old walls with wide mortar joints is to use a biggish bit of wood e.g. 4x2 inch if very wide joints. You cut it longish - e.g. 18 inches. You then hammer it into the hole in the mortar, then pull it out and trim off where the obvious pressure points are with an axe, hammer it in again etc repeating the process until you've got a good fit. then give it a final heavy hammering to make a tight fit. You then saw of the excess leaving enough length for a final precise cut. Or the final adjusrment can be by hammering it in a bit further. You re-use the sawn off piece for the next hole and so on. Sounds a bit tedious but it's quite quick once you get going. For brickwork the plug is usually about 4x1 inch with 2 opposite corners axed off at a shallow angle to make a wedge - sort of thin diamond shape if you look at the end. Otherwise proceed the same as above.

cheers

Jacob

[Tony]

I wish. The combination of shale and lime mortar makes a solid structure, but the only way I've discovered of making anything stick to it is rendering the the whole area and trusting that enough dust free points remain to hold it together.

I'll certainly take a look. I kept my old Morris Traveller on the road for over 30 years by injecting fibre glass resin into the woodwork. Not to mention innumerable house window frames.

Shale is just compressed mud, which tends to split into layers when a hole is made in it. Sometimes a screw holds, sometimes not. But the biggest problem is the lack of flat surfaces so that the drill bit takes the line of least resistance (which isn't necessarily where you want it to go) but, again, I'll look. Thanks.

Tony.

[Tony]

My first thought. Second was Pythagoras. The diagonal is longer than the height, therefore the frame has to be built at right angles to the wall, then slid up it. Unfortunately the height is 2.4m and the width half of that.

I've tried many ways of stabilising the damned stuff, even spraying. Nothing seems to work; touch the mortar with a brush and all you get is a brush full.

I love it; the greatest thing since ball point pens. Have used it for almost everything over the years, even rebuilding the bottom third of an exterior door frame which was rotten. It's still there, 20 years on. Concrete too, but I don't think it will stick to shale, which seems to be dry, soapy and dusty all at the same time. But thanks for the suggestion.

Tony.

[Rob Graham]

Not that it is of any use at all but I'm in West Lothian which has huge shale deposits which were mined until about 50 years ago and retorted to obtain oil. It may be that all shales have oil in them which makes it difficult to get anything to stick to them. Dooks are I suspect the answer - dwangs are the timbers that go between them - and Jacob has given a good description of the process.

Rob

[G&M]

We have a random gritstone house and ended up fixing the battens to the ceiling and floor. This also has the advantage that no ingressing damp (plenty in a stone house) can get to the sheet material, though we also ventilate it well.

[Tony]

That's the bit I don't fancy, Jacob. Trying to make a cut parallel to a wall, and an inch from it, sounds like a great recipe for skinning one's hands but, since that's how it's done, so be it, unless anyone else comes up with something less potentially exhausting and painful (:-) Many thanks for the precise instructions. They are very helpful.

Tony.

[Andrew May]

Sounds a perfect excuse to go buy a Fein Multimaster then....

Excellent for trimming in hard to get to places.

[The Natural Philosopher]

If its really that loose and crumbly ther are a few other dodges you can use to stabilise.

You can thin epoxy resin with acetone or cellullose thinners. That REALLY penetrates then. Another dirty trick is *thin* cyanoacrylate. This stuff simply wicks into porous structures. Get it from a model shop. Once the surface is more or less bound other brushable solutins can be applied to make a better job.

Even ultra thinned PVA willl stabilise loose muck into rock hard plastic in time, but it doesn't key to two pack resins.

[Tony]

Never tried thinning. Sounds good. As for cyanoacrylate I'm very wary after using it to stick some pipe cleaners together in a wire model project. Suddenly, it gave off white fumes, presumably cyanide. Only two breaths, but I was ill for two days. If that's how Americans kill their murderers, give me hanging any day

- death in less than half a second with a 6 ft drop. But, to the project in hand. I'm beginning to think that rendering with a 1:1:6 cement, lime, sand mix may prove simpler. It's something I was trying to avoid. The prospect of, in my 70's, mixing 30 yds from the house, running up with the mortar, applying it to the wall and dashing back for the next load, until finished, is not going to do a lot of good to arthritic joints and a slipped disc, not to mention my heart and disposition. But 'er indoors needs a shower - too many prostheses to get into a bath - so 'needs must when the Devil drives'

Tony.

Omit cymru to email.

[Ian Stirling]

There exist mixers hirable from your local tool-hire place, that will go through a standard doorway.

Add a thick tarpaulin, and being careful about spills may be enough.

[Ian Stirling]

Might be an idea to consider a mixer. There are little ones that will fit through a standard doorway. Add sufficient carpet/... protection, and it might help.

[jacob]

Fixing top & bottom is to make a studded inner wall rather than lining the wall. I'm doing this at the mo with my chapel conversion - uses fair amount of timber 3x2 inch but is quick, but in a small room might take away too much floor area. I'm also damproofing by hanging polythene off battens, and insulating with kingspan in between studs - if you are doing studs you might as well add insulation or its a wasted opportunity. Perhaps the sensible choice is between direct render/plaster or studs.

cheers

Jacob

[Nick Brooks]

Hanging isn't quick. You die because the rope cuts off the blood supply to the brain not because you can't breathe. If your neck breaks as you hit the bottom then you can't swing you legs wildly in your last few seconds but this probably adds to the pain rather than reduces it. The heart stops beating a few minutes later.

Nick Brooks

[The Natural Philosopher]

Its not norally cyanide, but its VERY unpleasnat and causes asthma.

Umm. Seriously, try the thinned epoxy/carbodyfilla route.

[Tony]

Excellent suggestion which I shall bear in mind for any future project. Unfortunately, it will be difficult here because I have to negotiate 3 doors then work in an 11ft by 5ft room with shelving on one side and a freezer and washing machine on the other occupying 2/3 of it.

I suppose I could get my old Baby Belling a bit closer to the house and turn the dash into a gentle stroll (:-). Did you know that, since European harmonisation, an old Belling can't be tipped into a new barrow? It has to be mounted on blocks because the barrows are higher.

A point of information for anyone faced with a similar type of job: spraying several times with 1:4 pva/water makes a pretty good job of stabilising the mortar which, contrary to my earlier assumption of sand/lime, is actually soil/lime. At least it's not difficult to remove.

As to replacement, I'm wondering whether I could do it in small patches? I've cleared an area of a couple of square yards but can go no further until the old belfast sink has been moved into an outhouse, into which the washing machine will go. If so, I can do the job piecemeal, which would be much better all round. It shouldn't crack at the joints, unlike hard mortar, especially if I treat them with with pva.

Opinions, especially experienced ones, welcome.

Tony.

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[Tony]

Sorry, Nick, you're wrong, unless you are referring to people hanging themselves on dressing gown chords behind the bathroom door. The old Home Office hanging formula, which I have somewhere, is based on simple physics i.e. Force = mass * acceleration, the object being to snap the spine, without pulling the head off - if you've ever killed a chicken you will know what I mean. The height of drop is proportional to the mass (weight) of the victim, as the table makes clear. Thus, heavy people have shorter drops than light.

A Canadian prisoner, a few years back, condemned to hang, went on an eating spree and raised his weight to over 30 stone. He escaped the rope because the Supreme Court ruled it a cruel and unusual punishment to hang him, presumably because the table didn't cover his case, or he only had a 3 inch fall!

As to the time, this relies on the fact that The drop = 0.5*Universal gravitational constant (approx 9.8 metres per sec, per sec) * time^2. If you transpose this formula, the time is, (for a 6ft(1.8M)) drop, is the square root of (I.8/4.9) which is about 0.6 secs.

Tony

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