Painting a Metal Roof
Preparation
Our metal roof is made of terne
metal.
It had been painted over the years with a regular roof paint.
Where the metal seams had bent, the paint collected as hard
blocks. As you can see from Photo A, the paint had
peeled off and the roof rusted. An examination showed that
the metal was solid.
The first job was to scrape all of the loose rust, dried
paint chunks, and roof
cement which should not be used on a terne metal roof. The
roof was power washed and a metal putty knife was used to scrape
the rust and old paint. Although it isn't recommended to use
a metal implement to scrape the roof, it was the only way to
remove the loose rust and old paint. You have to be extremely
careful not to pierce the metal. Photo
B shows
an area that has been scraped. During the scraping, straighten
up any bent seams.
After the scraping, the roof was power washed and a strong
solution of TSP brushed
on. This TSP solution was then removed using the power washer.
A hose with a nozzle probably would have worked as well as the
power washer since the scraping and TSP solution took off all
of the loose material. Finally, a chlorine solution was
washed on to remove any remaining moss that was growing on some
of the roof panels.
Because the gutter supports were nailed through the roof, I
removed the roof cement they were covered with and then covered
them using Preservation Product's Reinforced Restoration
System (see below).
The Preservation Product's restoration
system required the following steps:
- (1) A rust inhibitive primer coating was painted on the scraped
roof using both a brush and roller.
- (2) Each gutter support and surrounding area was coated with
an acrylic coating and a high strength stitch-bonded reinforcement
fabric was embedded into this wet coating. See Patching
a metal roof.
After two weeks
of scraping the roof was ready to paint.
Painting 
Metal roofs should be painted with a specially roof formulated
acrylic latex which bonds tightly to metal and becomes
a flexible coating 15-20 mils thick. Two firms are recommended
(see below) for their products. On the main roof, I used Calbar
Shower-Proof WB and on my porch
roof,
Acrymax from Preservation Products. Both
require priming over rusted areas. Two coats were applied.
Preservation Products offers a good
description of the advantages of these acrylic
roof coatings for metal roofs.
Product information:
Preservation
Products More
information »
Calbar
Roof Paint/Penn Valley Paint More
information »
Visitors:
| 
A.
The rusted roof
