How to repair a peeling deck stain

Q:  I had my back deck painted with DeckOver in spring 2016. A year later, the coating is peeling off in a few places, exposing bare wood. What to do?

A:  Behr, the manufacturer of DeckOver, describes this coating as a stain, but it certainly fits the definition of what most people consider paint. It’s opaque, hiding the wood grain, and it goes on thick and sits on the surface of the wood. It even fills cracks and gaps less than a quarter of an inch wide, something that makes it seem more like half paint and half putty.

The peeling you’re seeing could have a couple of causes. The surface might not have been cleaned thoroughly, leaving loose fibres. The coating could have stuck to them just fine, but if they weren’t stuck to the underlying wood, they and the coating could have peeled off. Or the initial coating might not have been thick enough.

Behr’s instructions for DeckOver specify that you need one gallon for the required two coats on each 75 square feet of deck.

“You have to measure your deck,” said a Behr customer service rep, who by company policy was allowed to give only his first name, Josh. “You can’t just eyeball it. It will look very nice after one coat. But it needs a certain mil thickness in order to last.”

When dry, that’s 10.9 mils, about the thickness of three sheets of copy paper.

What to do now? First, remove all of the loose coating. The easiest way is with a power washer. Make sure the pressure is set no higher than 1200 psi, which shouldn’t damage DeckOver where it is well-adhered but should take off all the loose material, Josh said. Then let the deck dry for several days. During the interim, sand any rough edges on the wood or where an intact section abruptly changes to a peeled section. The idea is to eliminate any sharp edges, where coatings have a hard time gripping.

Once the deck is dry, clean the surface with Behr Premium All-in-One Wood Cleaner No. 63 ($13.47 for 3.8 litres, homedepot.ca). One container this size, diluted with an equal amount of water, treats 400 square feet. Working in sections, dampen the surface with water from a hose, spread a liberal amount of cleaner with a pump sprayer, brush, mop or roller, and wait 10 to 15 minutes. The cleaner should not dry on the surface during that time, which is the reason to tackle only a small section at once. After the wait time, scrub the area with a stiff-bristle broom or brush, then rinse. Do not use a power washer this time, unless it is set for a very low pressure: 500 psi.

Why must the deck dry for several days? Josh said that after five to seven days, the cleaner loses its effectiveness in preparing the surface to grip well to the coating. So if the deck is too damp when the cleaner is applied, the wood won’t dry enough during the window when you need to apply the coating.

When the deck is again dry, if there are relatively few bare spots, touch those up, wait three or four hours, then give the whole deck a fresh coat. If there are lots of bare spots, skip the touch-up and give the whole deck two coats.

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