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Dismantling old trusses


saveasteading
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Unfortunately we are having to remove a section of building and replace (I wouldn't, and think they can be fixed, but have not prevailed, mostly because we can't get builders or designers to do tricky stuff.)

So 40 tied trusses have to come down. The wood is good apart from a few ends, and can be reused for roof or inner walls.

Any tips on how to get 50 year old twist nail connections undone? Either up in the air if the demo people will consider it, or on the ground once chain-sawn apart.

2 twist nails per joint, right through 2 x 45mm, and 30mm extra length bent back.

 

For the interest of anyone....interested. I calculated the design using the Scottish Government 'how to do it' guidance for 'non-Engineers'. Tied trusses with ridge plates, and some shear walls.

The local Engineer we are now required to engage is specifying Ridge beams (big) and props, and no ties: I guess because they never have to use the simpler, standard method. Then another ridge beam and some steel beams to support the ridge beam! 

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Have a good look at the timber joint. You'll probably see the timber has cupped a bit and there is a tiny gap. If so I would treat yourself to a Sable saw and buy some stiff metal (hack saw) blades for it. Also get some wood blades at the same time as you then use the sabre saw for a whole load of other stuff. Get in about it and cut the nail at the timber interface. If you try and prise it apart you probably wreak the wood.

 

Up in the air will be tricky as as soon as you cut one nail it will jamb the saw. Or use the chain saw and use the offcuts in the stove!.. the stove / chain saw is probably the way to go. You still will recover some good lengths for use in the garden and so on. Before you put it aside for garden use examine the timber as some could be really high quality and worth using for decorative purposes internally.

 

 

57 minutes ago, saveasteading said:

For the interest of anyone....interested. I calculated the design using the Scottish Government 'how to do it' guidance for 'non-Engineers'. Tied trusses with ridge plates, and some shear walls.

The local Engineer we are now required to engage is specifying Ridge beams (big) and props, and no ties: I guess because they never have to use the simpler, standard method. Then another ridge beam and some steel beams to support the ridge beam! 

Yes interesting. I think there is a bit more to this. Some sketeches would be helpful.. just some line diagram stuff on a few sheets of A4. These old roofs and traditional type design often need a bit of finesse. Sometimes the solution is staring you in the face, but you can't see the wood for the trees. The next trick is to know how to prove it using modern calcs.. but this can on occasion be time consuming as you need to convince the checking Engineers that the design is valid.

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On 03/02/2022 at 20:54, Gus Potter said:

use the offcuts in the stove

Can't do that as we had the whole roof sprayed, and I don't fancy the fumes. Not as bad as tanalised by a long way but too risky I feel.

 

I forgot some old floor boards had been sprayed before removal, and put some on a wood-burner.....despite them being ultra dry and porous with worm holes, they didn't burn well at all and made a lot of smoke.

 

The timbers are the right size to try slicing in half, and can then be used as our wall studs. There is some worm but really not significant and now treated. 

What shape they will take when split we don't know yet.

Failing that they will form the terraced garden.

 

Re. cutting with a sabre saw.... having tried similar with a multi-tool I found it was slow and burnet a lot of blades. 

A disc-cutter that could fit on a sabre saw would do the trick, but doesn't seem to exist,

 

On 03/02/2022 at 20:54, Gus Potter said:

how to prove it using modern calcs.

That is the issue I think. The approved design method is driven by tradition and evidence rather than calculation. As it is designed for use by non-Engineers (or Engineers who don't do calculations any longer) , the consultants will never have handled the document, and so revert to what they can calculate....it is costing us a lot and would be much worse if I couldn't argue some points which 'may be justifiable'.

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12 hours ago, saveasteading said:

Old fashioned, lever the tails up, knock them through and claw hammer/nail bar?

With the twist on them, does the levering/mole grips work?

 

I once had to take apart a significant proportion of the roof on an 1840s workers cottage in situe and salvage the timbers for reuse. Two tools I came to love for this are 1, a japanese nail puller, 2, A nail puller similar to this Hultafors version I bought years ago in Sweden https://www.hultafors.com/products/hammers/H0208-nail-puller-atle/79452 - I've rescued a good number of floor joists from metal hangers with this tool too.

 

Both will put out square twists as once they're dislodged, they pull out realy easily.

 

If you go for cutting, then a circular saw with suitable blade for chomping nails work well, providing you can support the truss to avoid pinch.

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Bolster driven between timbers with a big lump hammer will cut some nails if not too thick. If not the gap created will allow an angle grinder with 1mm steel blade to get in there.

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13 hours ago, Russell griffiths said:

throw the small bit and metal work on a bonfire

The 'small bit' is 1m long as the ties are quite high (hence the walls displacing in the first place). 

It might be the solution though, if we cut the ties off close to the rafters, losing 2 x 300mm, then try to get the stubs off on the ground, salvaging most of the wood.

 

This tool looks 'the business'. 

12 hours ago, SimonD said:

A nail puller similar to this Hultafors version I bought

 

 

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5 hours ago, saveasteading said:

The 'small bit' is 1m long as the ties are quite high (hence the walls displacing in the first place). 

It might be the solution though, if we cut the ties off close to the rafters, losing 2 x 300mm, then try to get the stubs off on the ground, salvaging most of the wood.

 

This tool looks 'the business'. 

 

 

Will it actually pull out a twisted nail?

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yeh those type of nail pullers will pull out twist nails easily, if they are hammered through and bent over i would first cut off the bent over bit with a grinder with a slitting disk, and then give the nail a good smashing from the back, this will break the "seal" that the nail has, always funny trying to explain to people the best way to remove an old nail is to hammer it in first ??

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On 06/02/2022 at 01:22, saveasteading said:

This tool looks 'the business'. 

 

On 06/02/2022 at 07:02, SteamyTea said:

Will it actually pull out a twisted nail?

 

Just came across mine - battered and well used. Works well with square twist nails and with the one I've got, you can smack the handle even with a lump hammer to get those stubborn nails out.

 

 

IMG_20220209_132342516 - Copy.jpg

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