Thread: Screwing Merbau to steel joists

Hi, I did a deck on our houseboat, merbau on C channel, but same principle.

I used self-drilling countersunk metal screws, but pre-drilled them with a drill bit just under the size of the drilling tip on the screw. I also countersunk the merbau so that the screw head would sit just under the top.

Thanks Big Shed: I am certainly going to countersink the Merbau so the screws dont sit proud.

http://www.jamestowndistributors.com...tainless+Steel

Do you think these screws would be good for this job? If not can you link me to some that would so i know what to get.

Thanks in advance.

Those screws wont hold in steel.

Thanks Doogie. Anyone able to link me to something that will?

http://www.redboxhardware.com.au/ind...id=84&gid=1241

These look like they might do the trick. Can someone confirm this for me. Also what size screws should i get? The Merbau will be 90 X 19 and the joists are 2mm RHS Gal.

My reference site is playing up - http://www.kjbolt.com.au/products_cat.php


cant get you a link to the exact screws you need atm

No worries doogie. When you can access it that would be greatly appreciated mate.

How big is your deck - a lot of ppl are now gluing decking down to duragal joists - a bit slower but very easy and durable. There seems to be some issues with penetration of the joists. These KJ bolts people have decking glue which is being used more and more.

http://www.kjbolt.com.au/newproducts_02.html


the screw at the top is the sort you might want to use - notice the drive tip for going through metal - these go in much easier if you drill a pilot hole through the timber and through the steel.

Thanks Doogie, The deck is huge and call me old fashioned but i like the idea of screws. I just dont trust glue

OK I got sick of constantly having this debate, so I've rung the OneSteel technical guy and asked him why they don't recommend screws on outside decks and verandahs. So here's what he told me:

1. You put a joist tape on the top of the joist which seals against the nail as it penetrates - this doesn't work with screws. Using screws can therefore allow moisture into the joist.

2. When the decking expands, screw heads have been known to snap off. Timber joists allow for a bit of expansion, steel doesn't.

He said that their preferred fixing method for external applications is a stainless steel twist nail.

If you insist on using screws, he says you can put a blob of silicone under each screw, or counter sink and then fill the holes - but this wont help with the head snapping problem.

With their own products, they wont assist in warranty cases if the decking has been screwed down.

Hi Silent - did the onesteel dude say anything about gluing decking down.?

Didn't ask him, hadn't read your post!

The only thing I'd say about it is that you wouldn't be able to put a joist tape down first...

There's a type of deck fixing available that grips boards from the sides - no through nails. I reckon if you could tek-screw that to the side of the joist with a bit of flashtak behind it, that would be the Rolls Royce.

Yeah I agree Silent - a batten of some sort down the side of the duragal joist sealed with nuetral silicone seems to me to be the best way. The KJbolt site which I gave a link to above lists a decking glue suitable for duragal joists - but I cant get into the site proper atm. Interesting stuff and links there also.

I think what Silent is referring to is a fixing that is screwed in between the boards and slots in to a slot in the side of each board.

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