Homeowner Forum / Construction / November 2006

"R Alexander" wrote...

More than likely it was galvanized with zinc.

A lot of coatings will not adhere to zinc unless it is treated properly.
Also unless you remove or treat the rust, it will just come back. So coating
or painting it could be a never-ending chore.  POR-15 http://www.por15.com/ 
makes a good product that's used for autos and marine equipment.

honestly once rust has started unless you can remove all
of the rust then your fix will only last a year or two

your fix could be harder then replacement

They do have better grades of metal roofing with an epoxy over
the galvanized metal.

Thats probably your best bet but if you only have surface rust
you should get another 10 years before you need full replacement

try your patch as long as it dosent drive you insane and save for
a new roof and maybe a catchment so you can save some of that
rain youve been getting lately and put it on a garden

Financially speaking, there are different alternatives to "repair/cover" the
rust issues. Some work 'sort of' and some don't. From your post & the time
factor you state, I'd highly suspect the existing roof is corrugated
galvanized sheetmetal. The 'sort of' would need to be researched carefully
and applied properly as there's way to many 'this'll work BS' claims out
there. You can probably get another 3~5 years of use with a proper
sealant/application to "seal in and/or cover the rust".

However, in the grand scheme of things, I've seen the (untreated) rusty
roofs hold up (no leaks) even though the top surface has severely degraded
and you're left with what is basically the bottom coat of galvanizing.

You have different options here as a way to go;
1. Attempt a repair. You might try a clean/repaint. (zinc-rich impregnated
paints)

                              You can try to cover/seal it with a asphaltic
based material (per your post) Used to be called Kool Seal
                                      > I've considered swabbing that
aluminum colored tarry stuff that folks put on
                                      > top of mobile homes.  How long
would that hold up before I needed to repeat?

2. Strip the old and replace with new metal roofing.

3. Re-roof over the top of the existing. This option is more in line with
industrial/commercial construction for roof repair but is cost effective
given the square footage of most industrial/commercial applications.

Assuming the cost factor will come into play here, I would personally opt to
re-roof with removal of the old. You should then be able to look forward to
at least 20~25 years of a worry free roof. The nice thing about the new
metal roofs are the cool factors built in. Essentially a type of paint that
reduces/reflects heat transmission/absorption. Trade speak is 'cool roofs'.

One KEY FACTOR in buying/installing a new metal roof is the refutability of
both the manufacturer and installer. The best product in the world installed
by monkeys will fail. The converse is true relative to installers vs
materials.

Dan

...

Depends on how badly it's rusted -- if it's just cosmetic so far, the
rust converters are probably the most effective solution and can last
quite some time.  One is at

http://www.bestsupplychem.com/

but a google search will turn up many others or you may find a local
farm supply or other similar outlet locally...