Ask the Carpenter: How to remove pine sap from a deck

Ask the Expert Home Improvement
If you don't seal your deck, you'll regret it in a year or two. Adobe Stock

QMy home is surrounded by white pines. This past summer we experienced the worst pine sap droppings in 20 years. Our deck is covered with dried white splotches. We have tried to remove them with several products, but nothing has worked. We need to re-stain the deck this season, so I’m wondering whether you can recommend a product to clean the deck. Can we stain over the splotches?

W.M., Plymouth

A. My first thought is to reach for a chain saw! If you’re re-staining the deck, it might make sense to give it a light sanding to removal all of the contaminants, and then clean the wood surface.

Unless your deck has a good finish, I would hesitate to use an oil-based chemical cleaning product. Some folks use nail polish remover or Goof Off, but again, I’m hesitant. You could end up with wet-looking spots where you use the chemical.

I would use a paint scraper, then lightly sand. If your deck is stained, use the paint scraper, but be very careful not to scratch the surface of the wood.

If your deck is unsealed, lightly sand the entire surface and seal it, either with a transparent product or stain. If you don’t at least seal it, you’ll really regret it in a year or two.


Q. I purchased a single-family home in Medford about eight years ago. It was built in 1920, and all of the floors were carpeted. I removed the carpet and found oak floors underneath that were in beautiful condition. Now, however, there are random gaps between the boards. What causes this, and what can I do to correct it?


A. Gaps in wood floors are normal and occur when the wood loses its moisture content.

Often, gapping can result with flooring installed during periods of higher humidity. Months later, usually during the heating season, those gaps start to show up. The good news is that they usually close back up. Many times, a seasonal gap, one into which you can fit a dime, will close in higher humidity.

Indoor humidity imbalance can also cause gapping. The ideal humidity level is 40 to 60 percent, and the ideal temperature range is 60 to 80 degrees. All the wood in your home will expand or contract as the moisture in the air changes. You may also notice that your doors or wood windows will swell and stick when it rains.

If you have large gaps that don’t close in the summer months, you may have excessive moisture (check the crawl space below), flooring too close to a heating vent, incorrect nail spacing, or structural settlement issues.

For normal gaps, no repairs are needed. Adding filler is not a good idea; it will get pushed out as the wood expands with moisture.

For larger gaps that don’t close up, call in a professional contractor who can repair floors properly. The best times to repair hardwood floors? April and October.

Rob Robillard is a general contractor, carpenter, editor of, and principal of a carpentry and renovation business. Send your questions to or tweet them to @robertrobillard. Subscribe to our free real estate newsletter at