Ask the Carpenter: Reader’s new porch is rusty, rotting

Ask the Expert Home Improvement
A reader's new deck is rotting where it is nailed. Handout

Q. We have a lovely front porch on our three-decker that the previous owners fixed up about five years ago, including replacing the decking, railings, and trim. Unfortunately, several nails in the balusters and trim are beginning to rust. In at least one area, this is leading to rot in the wood. I suspect that an unsuitable type of finish was used on the fasteners. I hope we don’t have to replace the balusters and trim. Is there’s anything we can do to prevent the rust from spreading?


A. It’s January, so my deck skills are a bit rusty (kidding), but I think I can help you here. Your first step, unfortunately, is to replace the rotted balusters. My lumberyard sells finger-jointed mahogany balusters that are more durable, come preprimed, and work great. Make sure that you prime the cut ends, the end grain, prior to installing.

The biggest reason for sealing wood-end grain is because the end absorbs liquids up to 250 times more rapidly than other wood surfaces. To envision this, grab a bunch of straws and hold them together. These tiny straws wick up moisture over time from rain, snow, and roof splash-off.

Install these new balusters by pre-drilling and then toenailing galvanized finish nails. If you have a nail gun, use galvanized or stainless-steel fasteners.

It’s possible the former owners used ungalvanized nails. In the balusters that haven’t rotted, countersink the rusting nails. Scrape, sand, and prime these areas well, getting the primer into the nail holes. Once the primer is dry, fill the holes with exterior-grade wood filler, spot prime, and then paint.

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 newsletter at