# Forum Home Renovation Sub Flooring  support beams rust

## cranswick

Hi l looked under the house the other day and l theres about 7 or more large long metal beams running the lenght of the house, l think they are called the support beams. l noticed there was some rust starting to form on them, the house is only 7 years old and near the coast which l guess can make rust worse. Is some rust on them something to worry about or not, they look fairly large , thick and strong , do most support beams on houses have some rust , do l need to do something to get the rust removed, what sort of cost would that be?

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## joynz

According to Wikipedia: 
‘Although rusting is generally a negative aspect of iron, a particular form of rusting, known as "stable rust," causes the object to have a thin coating of rust over the top, and if kept in low relative humidity, makes the "stable" layer protective to the iron below, but not to the extent of other oxides, such as aluminum.’

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## r3nov8or

Given the location near the beach the builder really should have galvanised the steel, or used something else. Anyway I would say that if there is only a thin 'dusting' layer and there is no 'delamination rust' due to more severe issues then after 7 years it's probably as far as it's going to go. If you have access you could paint it with a "kill rust" type of paint and see if the rust breaches that paint in short time. If so, more probably needs to be done...

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## Marc

For steel to rust you need air and water. Salt acts as a catalyst and accelerates the process. If the moisture is low the steel may develop ferrous hydroxide, if the amount of water available is higher you get a more aggressive form of rust, ferrous oxide. 
if you cut the air off, the process will slow down or stop, depending how good the isolation is. if you paint over the existing rust, you will trap enough oxygen to allow the process to continue and since iron oxide grows in volume, the membrane of paint will peel off and the steel will be exposed again. 
Solution, steel brush and paint. If you use a paint containing zinc you will slow down the process further due to the galvanic reaction of the zinc in the paint. 
Galvanising he beams would have been the best, but now is too late, unless you contract a hot metal spray company. Probably overkill.  :Smilie:

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## cranswick

> For steel to rust you need air and water. Salt acts as a catalyst and accelerates the process. If the moisture is low the steel may develop ferrous hydroxide, if the amount of water available is higher you get a more aggressive form of rust, ferrous oxide. 
> if you cut the air off, the process will slow down or stop, depending how good the isolation is. if you paint over the existing rust, you will trap enough oxygen to allow the process to continue and since iron oxide grows in volume, the membrane of paint will peel off and the steel will be exposed again. 
> Solution, steel brush and paint. If you use a paint containing zinc you will slow down the process further due to the galvanic reaction of the zinc in the paint. 
> Galvanising he beams would have been the best, but now is too late, unless you contract a hot metal spray company. Probably overkill.

  Its dry down there , theres no water , is it possible a light bit of rust or ' stable rust' is nothing to worry about. Its a bit difficult to to paint the beams as theres not enough height to kneel only enough height to crawl , it would be possible to paint them but difficult to crawl the whole time down there. l was wondering roughly what sort of cost would l be up for to get someone to paint the support beams of an average 3 bedrrom house

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## cranswick

> Given the location near the beach the builder really should have galvanised the steel, or used something else. Anyway I would say that if there is only a thin 'dusting' layer and there is no 'delamination rust' due to more severe issues then after 7 years it's probably as far as it's going to go. If you have access you could paint it with a "kill rust" type of paint and see if the rust breaches that paint in short time. If so, more probably needs to be done...

  
Hi just to update, l had a guy look under the house, hos not a builder but his a handyman and welder and experienced with metal. He said there is a light coat of rust forming and as you said, he said the builders of the house should have galvanised the beams or painted them. But he said its nothing to worry about at this stage, he said it could take 50 years before it the rust  becomes a series problem. But he said just to check it every few years to see if its getting worse and he said if l wanted to he or someone else could probably paint over the beams with rust killer for around $2,000. Do you think l should get it painting over within a few years, does $2,000 sound a fair price.?

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## Marc

To paint over loose rust without sanding is most likely a waste of money. 
A second alternative is to spray the beams with fish oil or similar. Get someone under there with a spray pump and a gallon of fish oil.

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## r3nov8or

I'd probably leave it, but the fish oil sounds like a simple way to improve peace of mind. It's also something you could do yourself and quicker than painting

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## intertd6

> Hi l looked under the house the other day and l theres about 7 or more large long metal beams running the lenght of the house, l think they are called the support beams. l noticed there was some rust starting to form on them, the house is only 7 years old and near the coast which l guess can make rust worse. Is some rust on them something to worry about or not, they look fairly large , thick and strong , do most support beams on houses have some rust , do l need to do something to get the rust removed, what sort of cost would that be?

   The real areas of concern are the places of contact where the loads are transmitted, what will happen is the steel will corrode & layers of rust scale will develop & expand, this will jack up the beam & what ever lands on it.
inter

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## Blocker

I would suggest a coat of Penetrol as a cost effective diy solution.
Regards,
Blocker.

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## cranswick

Thanks for your answers, do most of you agree with what the handyman welder guy said that as the house is only 7 years old even if l left it and did nothing it would be 50 years before the rust would become a serious problem, l guess l would be dead by then so it wont bother me much  :Biggrin: or maybe because l'm 3 km's from the ocean in might rust faster, l hope not.
some of you guys mentioned spraying it with fish oil, never heard of that before, l guess it would be a lot cheaper and easier then painting it. Would fish oil be as effective as spraying it with rust killer or painting it? if l sprayed it with fish oil or rust killer , would l have to keep doing it every 5 or 10 years?

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## doovalacky

Nearly every project built house I have worked on in WA has black steel for support beams. A light surface rust is normal and generally does not extend past that even after 30+ years.  
The only issue you may have is the proximity to moisture being under the house. 
Rustkiller paint is surprisingly effective if it is only surface spots.  I've got some stands that have been out in the weather for last 8 years and the rust is only just starting to show through again now.
Oil is an old trick that many use to slow down the process by reducing available oxygen.
Either way whoever does it will have to be careful if a sprayer is used. Confined space with little airflow is a recipe for disaster.

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## r3nov8or

> The real areas of concern are the places of contact where the loads are transmitted, what will happen is the steel will corrode & layers of rust scale will develop & expand, this will jack up the beam & what ever lands on it.
> inter

  Hey cranswick. Is there a moisture barrier between the steel and the supports? Malthoid, membrane, or similar?

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## cranswick

> Hey cranswick. Is there a moisture barrier between the steel and the supports? Malthoid, membrane, or similar?

  l dont think so,l would need to take another look. It seems pity dry down there the only parts that would get wet and the parts running along the edges of the house where a bit of rain could blow in from the wind

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## r3nov8or

> l dont think so,l would need to take another look. It seems pity dry down there the only parts that would get wet and the parts running along the edges of the house where a bit of rain could blow in from the wind

  It's not so much whether it's visibly wet. Moisture from the ground can wick up brick, concrete and timber supports into beams/bearers, if there is no moisture barrier. What are your supports made of?

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## cranswick

> It's not so much whether it's visibly wet. Moisture from the ground can wick up brick, concrete and timber supports into beams/bearers, if there is no moisture barrier. What are your supports made of?

  the supports or the vertical posts holing up the beams of made of metal, l think they are galvanised and not rust on them

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## r3nov8or

Ok, that's good. Then I would just monitor once a year and if it (the rust) seems stable, not do anything

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