Nails or bolts

[BigJock2005]

Can I tap someone's experience or professional knowledge here?
I'm mounting decking joists using BPC steel face-mounted hangers.
They can be fixed with 8 x 3.75mm twist nails or 2 x M12 high tensile bolts.

Any experience or recommendations on which is better?

Thanks

 

[^woody^]

One fixing per hole is the intended way, unless you want movement.

The larger holes are for heavy duty fixings and are in addition not instead of the other holes.

Won't these rust to high heaven in short time on a deck?

 

[JohnD]

I don't know how many you've got, but I use stainless outdoors.

large stainless bolts are expensive, so for the long ones, I buy stainless studding cut to size, which is fairly cheap, plus SS nuts and washers. If you have an angle grinder you can trim any round any protruding excess.

example
https://www.ebay.co.uk/itm/A2-STAIN...8-M10-DIAMETERS/361652370335?var=630988893452

You need the special stainless anti-seize compound.

Stainless does not need to be oversized to compensate for loss of material by rust.

I used to use zinc-plated studding, which is very cheap, but I had several rust completely through on fenceposts. They went through at the joint, possibly from chafing.

On the carport I used sherardised twist nails on similar hangers where they are under the roof and protected from weather, they are lasting well. Very difficult to remove if you make a mistake.

 

[BigJock2005]

If I was going to use bolts, they would be zinc-plated high tensile (nuts/bolts/washers) so should be no fear of rust.
If I use nails they will be sheradised twist nails, so again rust-proof.

Question really is whether I am better/stronger to use 8 nails per hanger, or to drill two M12 holes and use bolts. BCP don't recommend one or the other, but I think both might be a bit over the top? I'm looking at 24 joist hangers, so that's 1 pack of 50 of each for around £50 or a bag of nails for about £6.

But I'd rather just pay the £50 if bolting was materially better/safer.

 

[BigJock2005]

Actually guys, don't know I missed this on the BPC website, referring to multi-truss joist hangers:
Quote: "Use 30 x 3.75mm sheradised square twisted nails in all pre-punched holes, together with bolts in Multi Truss Hanger range where required. Stainless steel hangers are available to order."
So I'll over-engineer by getting in 50 bolts/nuts/washers plus nails. £50 is bearable for peace of mind.

https://www.bpcfixings.com/joist-hangers-timber-timber-connectors.php

 

[opps]

You need the special stainless anti-seize compound.

Wow, that stuff is expensive, £125 for a 500g tub.

https://www.ffx.co.uk/tools/product/Rocol-Roc14143-5024747900732-Anti-Seize-Stainless-500G-14143

 

[JohnD]

you won't need 500g

I use this stuff between stainless and aluminium alloys

https://www.ebay.co.uk/itm/New-50-g...766531?hash=item288fb61483:g:Zw4AAOSwe-heXrY7

the anti-seize compounds might look like grease, but are often based on slippery clay with additives.

it might be this, repackaged
https://brit-lube.co.uk/products/nickel-anti-seize

 

[opps]

you won't need 500g

I use this stuff between stainless and aluminium alloys

https://www.ebay.co.uk/itm/New-50-g...766531?hash=item288fb61483:g:Zw4AAOSwe-heXrY7

the anti-seize compounds might look like grease, but are often based on slippery clay with additives.

it might be this, repackaged
https://brit-lube.co.uk/products/nickel-anti-seize

That works out to 4 times cheaper than the Rocol version (per 500g). BTW, thanks for the link.

Forgive my ignorance- what function does it perform? The name suggests that it prevents nuts from becoming stuck. Is there the risk of the threaded rod shearing if you don't use the product and try to loosen a nut year later?

 

[JohnD]

some metals (especially stainless steel) are prone to cold-welding or galling when two pieces press and rub together. It's not like being too tight, or rusted together. It can happen in an instant while you're tightening a nut or stud. Once it happens, you can't undo it. You have to cut the pieces apart.

I don't know metallurgy, but there are technical papers describing how or why it happens.

 

[opps]

some metals (especially stainless steel) are prone to cold-welding when two pieces press and rub together. It's not like being too tight, or rusted together. It can happen in an instant while you're tightening a nut or stud. Once it happens, you can't undo it. You have to cut the pieces apart.

I don't know metallurgy, but there are technical papers describing how or why it happens.

Thanks for that. It isn't something that I have ever experienced.

 

[BigJock2005]

There’s no aluminium involved so I don’t get why I would need that.

Hangers are zinc plated, bolts are zinc plated, lock nuts and washers stainless.

From what I’ve read the cathodic reaction is minimal and doesn’t merit additional protection.