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Restoring rusted tin roofs

by Kendall Holmes
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Metal roofs will shed water for a century or more if they’re repainted occasionally. Eventually, though, these old roofs made from tin and its close cousing terne will begin to rust — and leak — if they’re neglected.

Is there any way to save a rusty, leaking metal roof?

A few years back, I wouldn’t have thought so. But that was before I learned about — and used on my own houses – a series of roof restoration paints and fabrics from Preservation Products.

Restoring a metal roof using the company’s products consists of:

  1. Scraping and sanding off as much rust and old paint as possible;
  2. Once the roof is clean, applying a water-based primer using a roller or a brush;
  3. Embedding polyester fabric into this primer anywhere there are holes or worn spots;
  4. And finally, applying a couple more layers of water-based paint on top.

Sound simple? It is. And it’s a long-lasting repair too.

Roofs recoated with Preservation Products’ coatings should last a decade or more before they need further maintenance — which itself should involve nothing more than cleaning the surface and adding a new layer or two of paint.

Paint: Heart of the system

Special paints, as you might suspect, are at the heart of this roofing system.

Marketed under the brand name of “Acrymax,” these paints are described by their manufacturer as  “elastomeric” – that is, they keep their elasticity at low temperatures. 

Acyrmax paints resemble (and even smell similar to) water-based acrylic latex house paint. You apply them with a roller or brush, which you clean with soap and water afterward. Aside from the super-stretchy nature of the paint, the key difference between Acrymax and regular paint is that these paints are thicker.

What you end up with, once everything is dry, is a coating of semi-gloss paint that is 25 to 45 mils thick. (By way of contrast, most heavy-duty contractor’s garbage bags are 3 mils thick.)

The products in action

I’ve used Preservation Products roofing systems on several sections of roofs on a pair of 1870s-era Victorian houses.

The first and most ambitious job entailed restoring a metal roof over an 18-by-14-foot sunroom of a Victorian home Deb and I owned until a year ago.

The roof (and the room) dated to around 1900.

When we bought the house in 1989, the roof was leaking badly. It seems that some years earlier, the nearly-flat roof had been enclosed with a fancy Victorian railing. That long-gone railing had been supported by three posts, each of which penetrated the tin roof. At some point in the past, someone had removed the railing and posts — and then done a lousy job patching the three holes left behind by the now-removed posts.

]Now those patches were leaking like a sieve. Worse, it was winter. And we needed to patch the roof so we could repair water damage inside the sunroom. And so we covered the roof with asphalt roll roofing. Our patch job was ugly … but it kept out the ice, snow and rain.

Our hasty patch job lasted for 17 years. But by the spring of 2006 the roof looked like hell. It was time to either repair the old tin roof underneath — or spring for new metal roofing.

And so I tore off the roll roofing, removed hundreds of roofing nails — and then went to restoring the mess underneath.

Scott Bennung, the founder and CEO of Preservation Products, had assured me his company’s materials would allow me to restore the tin roof. I was mighty skeptical. But I decided to give it a try.

Here’s what the roof looked like once I removed the roll roofing. Notice all the nail holes:

Tin roof, before

Preparation consisted of scraping and sanding off as much rust as possible. To do this, I used a paint scraper and a stiff wire brush. I also wore an OSHA-rated dust mask, because terne (a close relative of tin) contains lead.

Here’s a wider-angle photo of me doing prepwork:

Cleaning the roof of rust

Key to this part of the job was removing all flaking or loose paint and then, with the wire brush, getting rid of as much rust and grime as possible. Finally, I needed to clean up the dust and debris my work had left behind. On this relatively flat roof, I was able to clean up using a shop vacuum.

Applying Primer

This was a big job – so I was working directly from a 5 gallon bucket of primer. I applied the primer using a roller that I dipped directly into the bucket.

After the first layer of primer dried, I applied a second — and then while this was still wet, I unrolled and embedded into the wet paint polyester cloth I’d purchased from Preservation Products.

The cloth is similar in consistency to cheesecloth. Its purpose is to add fiber, giving the paint something to adhere to in covering up holes.  (And remember, I had plenty of holes — hundreds of them from nails, and three big ones from where those porch railing posts had once been.)

Getting the fabric in place wasn’t so much tricky as it was messy. I was working, after all, smooshing the sfuff into wet paint.

Next I covered the fabric with another layer of gray primer. The fabric, combined with the multiple coats of primer, had covered up all the holes. I now had a water-tight roof.

Finally, once everything was dry, I applied a top coat of red paint from Preservation Products.

The top coat and the primer are actually the same paint, just tinted differently. The theory is that someday when the red topcoat begins to wear off, I’ll know that it’s time to repaint.

I was pleased as could be with the finished roof. All of the seams from the old terne roofing telegraphed straight through the layers of paint and fabric I’d applied. And that, of course, was my intent:

To transform my rusty, leaky metal roof into something that looked nice — and which doesn’t leak.

Smaller jobs

Since doing this first job, I’ve done several smaller jobs using leftover materials.  Two of these jobs consisted of cleaning up metal roofs over Victorian bay windows. The other two were terne roofs covering entry vestibules.

Two of the roofs had been gooped with roof tar at some point in the past, while the other two had been kept covered up with paint. In each case, preparation was similar to what I’ve described above: Plenty of scraping, sanding and cleaning.

But with these smaller roofs, I didn’t need to add fabric, because none of them had leaks or badly rusted places. And so, in each case, I applied a layer of primer and two coats of finish paint.

The cool thing about these smaller jobs was that in a couple hours’ time, I was able to transform ugly, peeling roofs into crisp roofs that look as good as new, and which shouldn’t need any further attention for another decade or more.

I like that.

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