strength of timber

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N. Thornton 21 years ago

Fwom:Zipadee Doodar (zipadee snipped-for-privacy@yahoo.com)

> Since your 'Local authority planning officer' recommended

'doubling up'

> presumably he also suggested some method of attachment. Can you say what
>> method of attachment he suggested, if any?
>Using PVA glue to BS 4051 with screws driven through at 6 inch

distance -

for storage purposes only remember. We are not talking a full scale loft
>conversion here.

Thats the standard method. I would not consider countersinking, you need to use screws meaty enough for the job, not tiddlers lost in big holes and wood like swiss cheese.

But.... whats your existing joist size? Very few houses have joists so weak you cant use them for box storage as is. There's a fair bit of miswhatnot about this subject.

NT

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Zipadee Doodar 21 years ago

The existing joists are 2.75 x 1.25 inches, but I would prefer to err on the side of caution - son's video collection of 'classics' (crap repeated every

2 days on cable) is extensive, and can be heavy if concentrated in small areas.

BTW, what would you consider to be meaty screws in this sort of application? I have abandoned any idea of countersinking - only considered it because I have a seemingly inexhaustable supply of 4 inch x 8s. I want to start the job before the local spiders wake up and begin clog dancing across the loft.......

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BigWallop 21 years ago

application?

They're only 3'' X 1 /12'' rafters? Geeso !!! I think I'd place some decent new 5'' X 3'' full joists beside them, so I could at least walk across them. They don't sound to robust at all, do they?

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N. Thornton 21 years ago

joists so

repeated every

I wouldnt even want to walk across those, let alone put boxes on them. Adding 3x2 on top should be adequate, but without knowing the length its impossible to say for sure. I would not put the 3x2s on the side, there wouldnt not then be the same strength there.

4x2s would give you significantly more strength, I do wonder about cutting such a corner when youre putting so much work into it.

As you walk on the wood it will bend down, as you attach new woodwork it will pull up. Its possible your ceiling may crack up a bit, but all can be repaired if it does. You can reduce this by some strong putting sheet wood down that crosses a few joists, walking on that rather than standing on one joist a time.

Screw size: youve got 5.75" depth of wood, 4" screws would only go 1" deep which isnt overly impressive for a load bearing structure, 5" screws should do nicely. With screws that size I think you'll need to predrill, otherwise you may end up with firewood.

NT

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adder1969 21 years ago

Does it not depend on a) how close together the beams are b) if they're triangulated into the complete roof structure, c) what kind of unsupported distance they have to span?

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Mike 21 years ago

Within limits but I think I could just about snap 2.75 x 1.25 with my hands.

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BigWallop 21 years ago

Same here. I would most definitely try to lay more robust joists between the existing ones, before I laid any boards to walk or store tings on. No matter how you try to strengthen these joists, you'll still have parts of the load over just one or two at a time, which isn't really a nice thought.

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John 21 years ago

I bet they drink Carling Black label!!

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strength of timber

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