Connect sheet metal deck to wood

[N3l]

Hi everyone,

I have been searching online for the right screws to connect a sheet metal deck and 2x4 wood joists.
I couldn't find anything on simpsons or itw buildex. Unless I was look at the wrong section. Most of them have wood to hot rolled steel. but im not sure if you can use that for a gage 16 sheet metal. Please see attached for a sketch.
Any suggestion please? Thank you.

 

[jayrod12]

Standard shouldered wood screws would be fine. Also called panhead or waferhead wood screws. Typically in these types of connections, the wood governs not the steel.

 

[dauwerda]

16 gage is fairly thick, but based on your picture it is being used as a roof - typically you would use something with a rubber washer for this. See the following link for typical screws used for post-frame buildings that use 26 or 29 gage steel sheeting.

https://www.fastenersplus.com/shop-by-product/construction-screws/metal-roofing-screws/metal-to-wood

 

[dik]

You should be able to source screws from the deck supplier... they may even match the colour... and they often have 'rubber like' washers attached as part of the screw head.


Dik

 

[XR250]

For 16ga, you will likely have to pre-drill the decking if you want a rubber washered screw. I believe the self-piercing ones max. out at 18ga.

 

[hokie66]

https://www.buildex.com.au/products/roofing-cladding/

 

[dhengr]

N3l:
I would not want the end lap in the decking midway btwn. the structural members, which your sketch shows, use 6’-11” pieces of decking. I would strengthen the main structural elements (2x structural sub-facia) out at the facia trim. I would want the structure spanning in each direction to have its own level/layer/plane. The long joists are the top layer, under the decking, they probably don’t need the flat 2x4 on top, but should have blocking btwn. then, and in line with (atop) the main frames. Then, the beams of the main frames are the next layer down and are an integral part of the main frames. Pay particular attention to lateral bracing and the cantilever posts, in both directions. 16ga. is certainly not the limit for self-drilling screws, whether you can get rubber washers and all in one screw you must determine. They should be installed at a high point on the decking for proper drainage, not in a valley. Put a layer of self-healing, sticky-back tape on top of the joists, before installing the decking and screwing it down.

 

[XR250]

@Hokie.

I doubt those will penetrate 16ga material. Did you see a spec for that?

 

[hokie66]

Sure, there are screws to go through 16ga, which is about 1.5mm. The site I linked has some dropdowns where you can find the following page. Commonly done in Australia, and the website is Australian, so not sure about in other countries, but probably just a matter of looking in the right place, which is a fastener supplier. Then you need the right tool.

https://www.buildex.com.au/technica...on-guides/drilling-and-installation-capacity/

 

[XR250]

@Hokie,

That is interesting. In the US, Buildex has a Trugrip screw but is limited to .048" (18ga) or 1.22 mm. it must be the same screw.

http://fastening-solutions.itwbuild...th-bonded-washer-self-piercing-screws/1272000

I have tried these on 20ga and they are tough to make work.

 

[dhengr]

Is the difference that the screw XR250 shows is a piercing point screw, and they are limited in the thickness that they can pierce before the tip blunts. While the screws that Hokie shows probably actually have a drilling tip, which will go through thicker base material, but they have limits too.

 

[XR250]

@DH,

I don't believe you can use a self-drilling screw in wood. That is why they have the piercing point screws.
I have not seen anything else in Buildex's catalog.
I used to go thru this with contractors in my LGMF days.
See what you can find and report back.

 

[hokie66]

I think I misspoke about the screws through 16ga metal. I am accustomed to using the thickness in mm. The OP said these were standard corrugated sheets, which don't come that thick as far as I know.

 

[N3l]

Thank you everyone for your help and suggestions. I've recommended to the client to use an 18gage instead of 16gage. I think he's fine with that.
However, the Trugrip self piercing are really pricey! They're looking for something more affordable and can be found in home depot. Is there any other suggestions?
Thank you for your help!

 

[XR250]

Might want to have him test a few first. They are a real pain to go thru even 18ga.

 

[hokie66]

These are the screws. But I think XR250 is correct. If the corrugated roofing is that thick, you will likely have to predrill, especially if fixing through the crowns, as is necessary for watertightness.

https://www.buildex.com.au/products...-timber-type-17s/3-type-17-roofing-to-timber/