Rust Protecting Steel Roof Beams

[dolly.samson]

Are there any standards in Thailand, and are they enforceable, for protecting steel roofing beams? I see that most builds have what appears to be a glossy red enamel finish on the steel, while a scant few just use a light grey primer. Those who use the red enamel, paint the joints where welding is done, while the scant few don't bother. I have seen already rusty beams being tiled over.

What effect will lack of proper rust protection have on the longevity and safety of a home? It would appear to this layman that rusty joints would be prone to break apart after some time.

[PAINTER01]

most of the primers I saw being applied when visiting various sites on my visits to HH (what a way to spend a vacation) are single pack white spirit based fabrication primers, most were also applied by low tech paint sprayers. You should normally expect a primer to be applied in excess of 100 microns (0.1mm). Given the chemical composition of this type of paint being used and the application methods I doubt this is being achieved (possibly as low as 25/50 microns).
This in its self is not a problem if the steel is corrosion free when installed and in a environment free from moister and away from high humidity.
The main steel span's them self won't rust and rot away the danger is on welds and joints. I also noted that some roof tiles are tied on to the steel spans using rusty wire laying around site (steel fixers type). This is a way of transferring corrosion to the steel pulin bars and this wire would be prone to rotting away with a short period of time.

Coming to HH again in 3 weeks and looking forward to visiting building sites again !!!!

[dr dave soul monsta]

Use timber !

P1 can a vernier be used to measure the paint thickness or do you need a electron microscope ?
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[prcscct]

[STEVE G]

Isn’t that red paint put on the welds the same red lead stuff that I was made to paint onto rusty bits of aircraft carriers during idle moments in my navy days?

[VincentD]

Hi Dr Dave

Timber is so expensive these days, steel has become a viable alternative.

You can use a wet film thickness gauge, it's like a series of steps on each side of a square bit of plastic with the two end steps at the same height and the corresponding thicknesses in between. After spraying on the paint, the gauge is stuck into the wet paint coating and removed. The paint thickness can then be ascertained by the number of steps covered in the paint.

The equipment to measure dry paint thicknesses is much more expensive and works on an eddy current principle.

P1, indeed, what a way to spend a holiday! I very much doubt they'd be using 'low tech' paint sprayers for roofing steel beams, as they'd need an air supply, hoses and such - on the roof - plus imagine all that overspray!! Possibly you've observed the roadside car/ truck body shops with that particular type of equipment. And, really, nobody is going to check their paint jobs unless a specification calls out for documentation of such...


DS,

They normally just brush on some iron oxide paint for steel roofing beams. It's quite effective.


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[Nereus]

[johnnyk]

If using metal then it can only really be protected by either galvanizing or anti-rust paint.
Neither is perfect but spraying on anti-rust paint seems to me to be the barest minimum. Some builders here dip the steel in paint baths ensuring a thicker coat and no missed bits for rust to attack.

[huahinsimon]

Are there building inspectors that inspect the build at any point in the construction like there are in Europe and USA? Can one hire a tessaban building inspector to look at the condition of work and approve or disapprove?

[johnnyk]

[Norseman]