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The 2 Biggest Myths of Sanding Exterior Porches

Exterior porch refurbishment is a great summer project, but misconceptions about the process abound.

Let’s debunk some of them.

Myth #1  Porches are easy and quick to sand. My porch is only about 300sqft and just has some paint on it. I’ll be able to sand that clean in a couple hours, right?

kirkhanson1It takes more work to sand a porch than you might think:

  • Porch paint is difficult to remove because it is dense and thick. Because it was intended to resist the wear of foot traffic, contains a higher percentage of solids than ordinary exterior paint. Paradoxically, even when porch paint looks worn and scratched, it is still a beast to sand off.
  • Every customer who comes to us with a porch with any paint on it, even when they swear up and down that their paint isn’t very thick, eventually resigns themselves to using the coarsest grits available, starting with 16 or possibly even 12 grit. That means you’ll take several passes, just to get the paint off, then more passes to get out the scratch from removing the paint.
  • Old porch paint is more likely than clear finishes to contain lead. And while it is perfectly legal for a homeowner to sand off this lead-paint bearing finish, the lead dust that you release will poison you and your neighbors. Do a Lead Check test ($4.95 here at the shop) and if it’s positive, hire an RRP accredited flooring firm. It will be worth every penny.
  • Porches in Minnesota are primarily installed the short way, meaning the boards run parallel to the short depth of the porch (see photo at right). That depth is typically only 7-8 feet, which makes it more awkward to use the drum sander.
  • Porches have railings. You have to sand under the railings. We rent a special radiator for that, but you still have to do it.
  • Because of their direct exposure to water, the individual boards of most porches are likely to be cupped and you’ll have to sand that curvature level before you can sand the boards clean. Luckily, most exterior porches are made with fir which is relatively soft and easy to flatten.

Myth#2  Outdoor finishes should last at least a decade without maintenance. Wooden boat decks were constantly exposed to the elements and they never rotted – you should be able to sell me something that lasts like that.

decayed porch floor side viewFloors in porches are exposed to more sunlight and more water than any other area of the home.  Water and sunlight are deadly –and let me say that again more emphatically, deadly, to wood. If you find a clear finish that lasts five years on a south facing deck, buy stock in whoever makes it because it must be magic.

So why did ship’s decks last forever? Because ships had untold numbers of abused, shanghaied sailors who scrubbed those decks with coarse brushes and sand every day. 

If you abraded your porch like that every day, you wouldn’t see any damage either because you would have sanded it off! But your porch was likely coated with something – porch paint or a varnish of some kind- and then simply ignored for years at a time.

Clear finishes will degrade very quickly on a porch because, unlike paint, they let the sun right into the wood where it can break down the lignins, which are essentially the connective glue that makes wood hold together. Once those lignins are broken down, the varnish has nothing left to cling to, and so it peels or powders away. 

Paints are better at protecting wood from sun damage – they are much like wearing a sweatshirt to the beach; they block the sun from reaching the wood. But paint still can’t block everything, and standing water from snow and rain, the weakening effect of sunlight, plus the erosive action salt and sand underfoot will eventually grind paint away too.

decayed porch floor top viewThe simple answer is that, no matter what finish you put on your exposed porch, you will have to periodically reapply a top coat of some kind, even if you use porch paint (enclosed, three-season porches are more protected so the finish will last longer there).

There is no magic bullet that will protect your porch forever; the longest you can completely neglect that wood is two years.

Two years?!?” we hear you cry. Yes. Two years. But the good news is that if you refresh or reapply a top coat to your exposed porch every two years you should be able to avoid resanding it for at least a decade.  But compared to the huge effort of resanding, recoating is child’s play and worth every minute of your time.

What product should I use? Right now, we offer two options. 

Waterlox Marine Finish.  We love it for four reasons:

  • This is essentially a “long-oil” varnish, which means it has a higher proportion of oil to resin, which makes it stretchier and better able to handle all the swelling and shrinking your outdoor wood will encounter through the seasons. 
  • The high proportion of tung oil in this finish also allows superior penetration of the finish into the wood.  This allows most of the Waterlox to cure below the top level of the wood, which makes it less likely to peel or flake, but it still has a lovely sheen.
  • Marine Waterlox has a UV protective component that slows down the destructive effects of sunlight. 
  • Its fabulous, rich, almost red color looks good on every wood type, but is especially attractive on the older fir and pine of many porches.

waterlox marineMost porches require at least three coats, and both Waterlox and Pete’s would recommend four coats, allowing at least 24 hours between each coat.  But because this is more of a penetrating finish than typical high-building polyurethane, it is particularly easy and forgiving to apply.

This product should be touched up or recoated at least every other year.

Marine Waterlox Gallon $130 (400-500sqft per gallon)
Marine Waterlox Quart    $50

Just call the store at 651-698-5888 if you'd like to order.
Sorry, because of the paint thinner component of this, we can’t ship this outside of the 7-state area of Minnesota, Wisconsin, Iowa, Illinois, Nebraska, South Dakota and North Dakota. 

Rubio Monocoat Hybrid Wood Protector. 
Five reasons we adore it:

  • HybridWoodProtector1LwebThe Rubio Monocoat is a linseed-oil-based, zero VOC finish – we think it smells great.
  • It is a one-coat finish that is water-resistant in 36 hours and ready for traffic after 48 hours – very helpful if you are trying to coat during the thunderstorm season.
  • It does not form a film layer of any kind and has a very matte appearance.  Flaking or peeling is essentially impossible because there is no build above the wood whatsoever.
  • The oil contains UV blockers to slow down the sun damage and mold inhibitors to keep the algae at bay.
  • It comes in seven colors – and the colors can be mixed with each other to increase your design options.

This product requires that you prep your wood (new or old) with their Exterior Wood cleaner. 

Covered porches will need an oil refresh every other year, but fully exposed decks will need touchups annually.

Rubio Monocoat Hybrid Wood Protector 1 liter  $160 (+/- 300sqft per liter)
Exterior Wood Cleaner 1 liter $52 (+/-250sqft per liter) and this is required before applying the Hybrid Oil!

Call the shop at 651-698-5888 to place an order - we stock Pure and the Exterior wood cleaner and can ship!