On 5/29/2011 2:19 PM, TN wrote:
Our front door has an oak front stoop that I have tried every
possible wood stain and polyurethane sealer on the market. No matter
what I use it starts cracking very spring and I have to sand it down
and do it all over again.

Does anyone have a product that can stain and seal oak so this is
more durable?

Thanks!

Are you staining and sealing all surfaces of the board or just the easy
part that faces up?

Instead of coating it with poly, try an oil that will soak in instead. I believe that for hard wood, Danish oil will soak in better than teak oil.

Jack:

That cracking and peeling can be due to two things:

1) the stoop is absorbing rain water or snow melt on it's underside.
As that moisture migrates up through the wood and reaches the top surface of the board, it evaporates with sufficient pressure to push any impermeable coating off the wood. This often happens with people who paint their garage or basement floors with epoxy paint. Any significant migration of moisture from the ground below water up through the concrete slab will result in that paint cracking and peeling.

2) the expansion and contraction of the wooden stoop caused by changes in it's moisture content.

Wood has virtually no thermal expansion or contraction, but it can swell and shrinks by as much as 14 percent depending on it's moisture content. The wood's moisture content will change with the temperature and relative humidity of the air surrounding the wood, and that changes from summer to winter. In this case, the coating is not cracking and peeling because it's being pushed off the wood by the vapour pressure of the water in it, but because that water causes dimensional changes in the wood that hard coatings (like polyurethane) simply can't stretch to accomodate.

Unfortunately, there's no easy way to tell which of those two things can be causing the cracking and peeling.

So, if it were me, I would plan to do the same song and dance as you have been doing two more times:

Once with an EXTERIOR alkyd paint or a clear marine varnish (aka: "Spar" varnish). This will give you the hardest coating that is still elastic enough to stretch and shrink with wood outdoors. You need that hardness for the coating to stand up well, both to that it doesn't wear off fast and so that it doesn't get dirt embedded in it under foot and ends up looking awful.

Now, if that oil based coating still cracks and peels, then I would assume the problem is that moisture is migrating up through the wood, and in that case you'd do better with a coating that will allow the moisture to evaporate through it.

And, that means using a water based coating. If it were me, I would use a water based clear coat like Minwax "Polycrylic":




... but if you live in the south where the sunlight is intense or in a coastal area where the high humidities cause mildew to grow on paint outdoors, then ask if there's a similar product available for exterior use. Otherwise, just use the stuff that's recommended for interior use and clean it with bleach periodically to kill any mold on it and hope the wood beneath it doesn't start to turn grey and fuzzy cuz of exposure to UV light from the Sun. (Exterior coatings will have UV blockers in them to block UV light and prevent that greying and fuzzying from happening to the underlying wood from UV light.

The acrylic clear coat will be softer than an oil based coating, thereby making it more prone to getting worn off sooner or getting dirt embedded in it underfoot, but it will at least allow moisture to evaporate through it and that should alleviate the cracking and peeling.

And, if it STILL cracks and peels, then there's too much moisture getting into that wood to deal with, and your best bet is probably to just stain it and treat it with a deck sealer and leave it at that.