How to stop roof screws rusting?

[Amrad79]

Hi my colorbond roof is 12 years old  . l live 4 km from the coast. Theres no noticable rust on my roof but l noticed about 10%-15%  of the roof screws have some rust on them , All the rest look normal . l think the rust just stated a couple of years ago. l was thinking just replace the rusted screws and treat the remaining screws that are not rusted with some sort of rust inhibitor product or paint to stop them from rusting. Could l do that or should l replace all the screws not just the rusted screws, What is the better option ? and what product to use to prevent the screws from rusting. My concern is if the rust could spread from the screws to the roof, but they have rubber washers under them which would help, how urgent do you think the problem is , could l wait a year to replace them, thanks

[Nailbag]

Hi @Amrad79 Looks like either those rusting screws are mixed with higher quality powder coated ones, possibly from 2 roofers fixing the roof off. If you feel safe/confident on the roof yourself, it's a very easy job of using a drill/driver or impact driver with the right sized hex bit and you could replace them yourself. Otherwise any handyman (cheapest option) could easily do this task for an hourly rate plus the fixings. 

Personally, I would get this task completed sooner than later. If the body of any of the screws is also rusting and making contact with bare metal in the holes it's made through the colour bond roof, could be the beginnings of corrosion spreading. At the moment from your photos, I would be very confident that simply changing the screws over will all that be required.

Nailbag.

[Dave-1]

Evening @Amrad79 

Sorry I just logged in and saw the question now about the screws. @MitchellMc has nailed it, well screwed it lol  Id be only replacing the ones with rust on them and would be thinking its a bad batch of screws. As he mentions, maybe take one or two out to check how bad the rust is and if its spread. 

I wouldnt class it in an "urgency" class, I would class it in a "have to get that sorted sometime tho.

Dave

[Amrad79]

Hi can l ask you advice l spoke to my plumber he said theres two options they can paint the screws with cold gal paint which is only a few hundre dollars but will only last a few years or they can replace all the screws for $2,000, which is a better option, l was thinking as only about 20% of the screws have rust on them and the other 80% look normal it might be better just to have them painted and check them in a year.  l mentioned to the plumber about just have the rusted ones removed but he said its better to either remove allof them or  paint them and check them in a year. My main concern is that rust does not spread from screws to the roof, if the screws are painted will that contain the rust for a couple of years

[EricL]

Hello @Amrad79 

It will probably work if the heads were painted with cold gal. The issue I have with this repair option is that you 'll have to check again in a few years to see if the cold gal is still holding up. Whereas if the screws were properly replaced then you would be confident that the screws are not deteriorating.

I suggest going with a full replacement rather than a half measure where you'll need to check down the line if it is still in good condition. Another problem with that scenario is if the cold gal fails rust could spread on your roof.

If you have any other questions we can help with, please let us know.

Eric

[Amrad79]

Thanks, yes l think l will go with either a full replacement or just the rusted screws pulled out, someone on the forum mentioned it could be a case of the rusted  screws being defective and the rest normal, ? is that possible or unlikely ?. Also when you replace the screws you will take the old screws out of a hole and insert the new screws in the same hole, does that mean that the screws wont have the same strong grip as the old screws and theres a risk the roof could come lose in the wind, if that happens then does the person who installed the screws responsible or would l have to pay the cost of fixing that

[MitchellMc]

Hi @Amrad79,

Galvanised screws should not have deteriorated to that state in 12 years, so it indicates to me they could be defective, given there are screws right next to them that are perfectly fine.

The replacement screws will hold the roof sheets down just as well and have the same strong grip as the current screws. 

Mitchell

[Amrad79]

thanks l live 4km from the coast, so should they still not have rusted after 12 years, so your advice is not to replace all the screws on the roof, just replace the rusted screws. , even if the cost of a total replacment is similar to just replacing the rusted screws?

[MitchellMc]

My opinion is based on the fact that some have drastically rusted, and some have not at all @Amrad79. If 12 years were the lifespan of those screws 4km from the coast, then all the screws would have rusted equally. The fact that only some of them have rusted adds credence to the theory that there was an issue with their corrosion protection.

If the total replacement cost is similar, I would be doing all of them to be safe. There is no point working off theories when total replacement would solve the issue entirely.

Mitchell

[Amrad79]

Thanks for your help , just to update , My plumber said his going to replace just the rusted screws and it will only cost a couple hundred, he said the vast majority are rust free and could be OK for a few more years so its not worth replacing all of them now, he will just replace the rusted ones and then check the roof screws again in a year

[Amrad79]

Thanks for your help l have another question, l think the plumber said he is going to use stainless steel screws but l read on the internet that they are not suitable for colorbond roofs and can cause rust, should l tell him not to use stainless steel screws or would they be OK? , what type of screws should l ask him to use for a colorbond roof. My other question is would it be OK for him to use the same sized screws as the old ones as they are going into the same holes, should he use a slighly larger screw so it has a better grip