Step 4: Priming Bare Wood

Priming bare wood (and other surfaces as needed) on the exterior of your house prior to painting is important because it seals off the porous grain and prevents the topcoat of paint from soaking in and losing its natural elasticity. Without this elasticity the topcoat will harden, crack, and start to peel much sooner than it should. So prime generously if you want to paint your house right!


When the washing, scraping, and caulking are done, the time has come to finally dip a brush into something fluid and spread it on the house. It’s prime time.

On the surface, priming does not appear to be a convoluted matter, and perhaps I’m guilty of assigning it more complexity than it deserves. Bottom line is you slap primer on any bare wood (or bare spackle and sometimes bare metal) anywhere on the house. You do this so the surface is sealed and it won’t suck the life out of the topcoat, causing said topcoat to crack and peel. End of story, right? Any baboon could prime a house.

I suppose. But that’s not going to stop me from presenting a primer about primer, and in the process relate one of the most valuable lessons there is to learn about painting: always perform the Fingernail Scratch Test before painting a house. The Fingernail Scratch Test is simple: you paint a small section of siding (trying on colors is a handy time to do this), let it dry for a day, then come back and scratch it with your fingernail to make sure the new paint is adhering properly to the old paint. You’ll know if it isn’t—it will peel off the subsurface like a boiled plum, clearly not sticking. Although this is rare, it actually happened to me on a house that had an old coat of oil-base solid stain on it; even the pressure washing hadn’t removed the residue. The entire house required a “bridge coat” of oil-base primer to fix the problem. If you perform the scratch test and don’t think you’re paint is sticking, consult with the manager of your local paint store to figure out what’s going on. You might need to do some extra priming.

There are only a few other salient points to make about priming. First, there is cause to wonder what exactly primer is in the first place. How does it differ from paint? More to the point, if you have a can of old paint sitting around, can you use it as primer to save money? In answer to that question, I will say that several bosses have instructed me to use leftover latex paint for priming interior drywall in new construction. As long as the leftover latex is flat or maybe satin sheen, I think it’s okay to use it for that purpose. On the outside of a house, though, I would stick to bona fide primer, because it’s not formulated exactly the same as paint, it’s tweaked a little so that it soaks in and seals more, not aiming for the same rubber-like skin effect.

The best exterior primers are oil-based, and they can be gummy to work with; stir in a small shot of paint thinner or some Penetrol to alleviate this. (The paint companies do make some water-base primers for exterior use; I would say that’s better than nothing but not as good as oil.) Use a brush and possibly a roller, depending on how much surface you have to prime (a mini-roller can also work well for priming). Be aware that some painters switch steps 3 and 4 around and prime bare wood before caulking the house to seal the surface before applying caulk; others prefer to prime after caulking so they can prime the caulk itself. Whatever. Just keep in mind that oil primer is prone to flicking drops around, so you’ll want to drag a drop cloth along with you and a thinner-dampened rag to quickly clean any mistakes. You might also want to mask (tape) off some windows and doors if you’ll be priming above or around them; see the video on masking (taping) the house and arranging drop cloths for tips on doing that. If you accidentally drip some primer onto a porous surface such as asphalt shingles or concrete, wipe off as much as you can and then sprinkle some dirt on the spot, grinding it in with your heel to obscure the evidence. Works every time. Don’t ever pour paint thinner on asphalt shingles.

One final note: If you have areas on the house where the paint is severely cracking but not actually peeling, consider applying a coat of Peel Stop, a clear primer that is designed to form a flexible barrier over cracking paint and prevent it from cracking anew through the fresh topcoat. Don’t have unrealistic expectations for zero cracking in the future, but this could help minimize it. (Watch the priming video for more information on Peel Stop.)

Go back to Exterior Painting Videos                          Move on to Step 5: Removing the Downspouts