How to install timber bearers onto a steel framed deck?

[HarryAudus]

My deck will soon need to be replaced, at least some of the boards. The problem is that the substructure comprises steel channel beams (sideways) and the boards have been screwed directly into the steel. Of course, these screws weren't stainless, and now they are rusted in. It looks like I'll have to grind them all out. I don't want to screw the new boards directly into the steel, so I'm thinking of screwing timber bearers side-on to the steel channel and then screwing the boards into the timber bearers.

I guess this method will only work if I replace the whole deck, not individual boards.

Does this sound like a good way to avoid screwing into the steel? Or is there another, better way? Any advice would be appreciated.

[MitchellMc]

Hi @HarryAudus,

I'd like to see some images of the steel structure before providing a detailed response. If you could post an image, that would assist our knowledgeable members in formulating helpful replies. Let me know if you need assistance uploading.

What you've mentioned sounds like it would work, but calling the timber "bearers" probably isn't the correct term. They are more like batons for the purpose of fixing the boards down. The steel C channels will still be bearing the weight, as the decking will be sitting upon them.

I agree that it could be a bit fiddly trying to do this work for individual boards.

How long have these screws taken to rust out? If they have successfully secured the boards for 5-10 years, then I'd be inclined to just replace them back into the steel. If they only lasted a year or two, you'd certainly want to look at alternative fixing methods. What were the screws made from? I'd imagine these Zenith 10G x 50mm Galvanised Countersunk Head Metal Screws would last for a significant amount of time exposed to the elements as they are for external use. Perhaps the screws used were not suitable for exterior use?

I'll be looking forward to those images and providing further assistance. Please let me know if you have any questions.

Mitchell

[HarryAudus]

G’day Mitchell.

Thanks for your email. You’re right – the timber pieces I propose are not really bearers but battens. And what I called channel beams are galvanised C‑sections.

The house was built in 1992, and so the screws have been in there for 30 years. Most of the boards are still pretty good, except at the edges where they’re in the weather, and I’m not in a great hurry to replace anything. But when I do need to get it done, I want to do it so the next person will be able to remove the screws and replace the boards much more easily. I hate work that’s a result of the previous person not thinking ahead, or not caring.

Anyway, I’ve attached 3 photos that I hope will give you some idea.

Thanks again for your advice.

Harry

[MitchellMc]

Thanks for that additional information and images @HarryAudus.

Thirty years is a good stretch from any deck fixing. After that amount of time, any screw exposed to the weather is likely going to be corroded. I'd agree that the screws being in steel are contributing to their shank snapping, but it's not uncommon to see this same issue in timber-framed decks.

How are the rest of the screws on the deck that are not exposed to the weather? If those can be removed without the head snapping off, and only the screws on the exposed edge are giving you trouble, then I'd be inclined to screw back into the steel C-channel instead of installing timber batons. If this issue occurred every five years, I'd be all for resolving it, but 30 years is a good trot.

Please let me know if you have any questions.

Mitchell

[HarryAudus]

All the screws as far as I can tell (obviously I've only tried a few) are rusted in. When it's time to remove the boards, they'll have to be ripped out and all the screws will have to be removed with an angle grinder. I don't want to leave the same problem for the next person, even if it is in 30 years time. That's why I'm thinking that attaching wooden battens onto the C-section steel joists, and then screwing or nailing (which is better?) the new boards onto the battens is the way to go. Probably quicker too.

[MitchellMc]

That makes sense @HarryAudus, especially if the next guy is you again. 😁

You'd screw the new boards into your timber battens. I prefer these self-drilling deck screws, as there is no need to predrill and countersink the holes. They'll save you a whole heap of time.

Mitchell