On Deck Post Systems
Our remodeling company was recently called to repair a leaking second story deck. The deck is located on the windward side of the house and leaks were showing up at adjacent interior walls and ceilings. Needless to say we found it necessary to remove an inordinate amount of surrounding surface material in hopes of eliminating any existing fungus damage. Leaks in tile decks can be disastrous to surrounding areas and cost a fortune to fix.
Since the deck was going to be finished with ceramic tile the deck post system suddenly became an extremely important consideration. We didn’t want the posts come up through the flooring because each penetration would eventually become a potential leak hazard. The tile detail extended over the edge of the deck in the same fashion as a countertop. This made connecting the posts even more difficult. We didn’t want them to penetrate the edge of the tile either. This meant we couldn’t bolt the posts directly to the side of the deck. What to do?
Since there was plenty of bolting area beneath the tile edge we decided to use thicker-than-normal posts and notch them at the tile edge. Thus, we were able to achieve a strong connection via heavy bolting at the deck perimeter and we did not have to worry about penetrating the waterproof surface anywhere.
Isn’t it amazing! Even a deck-post connection can be important. Also, “how a post is connected to a deck” can have a great deal to do with the deck’s appearance – and – how strong the hand rail is…. or not! We like to notch the post so that the rail system is centered over the edge of the deck. Others prefer no notch placing the rail system outside the deck edge. Also, we prefer a two-post corner system where others suggest that a single post system is cleaner. We prefer the strength of a two-post corner. We also prefer to use 4×6 posts instead of 4×4’s. Once the post is notched its depth at the thinnest point is not less than 3 ½” (a full 4×4). We also like to use vertical grain, clear-dry redwood when the budget allows because the material can be pre-stained before assembly (no waiting for natural moisture to evaporate). Also, clear material is stronger than the same material with knots, and vertical grain is simply the most beautiful wood in the world to look at.
We recently decided to begin using neoprene washers at the bolt connections BETWEEN the post and the deck edge. The washers act as spacers between the post and the deck and guarantee a free flow of air at the connection. We have found that wherever wood connects there is a chance for rot. All such connections have a tendency to hold enough moisture to promote rot. If you have read our articles in the past we mentioned the under-board deck fastening system. This is another step in reducing rot and improving the life of your deck.
When it comes to bolt connections – size IS extremely important. Each post should be connected to the deck with at least two half-inch through-bolts with the spacers we mentioned and malleable washers (they’re the big square kind) at both sides. Through bolting is important because it can be easily tightened later as the wood expands and contracts, which causes even the best of connections to loosen. In our case our customer’s deck already had a beautiful plywood soffit (ceiling cover). This meant that we wouldn’t be able to access the deck framing later on. We were forced to use lag bolts. We used large chunks of 4×6 blocking as backing for our lags. One thing we didn’t want to do is remove plywood siding to tighten bolts – kind of an expensive process.
It is really important to remember that spacing between parts in open rail systems is important. There should never be more than four-inches of clearance between any parts. Be careful here, some building departments require the space to be even less. Check with your local building official before beginning. By the way, deck rails should not be less than 36” above the deck. Your building department may require 42”. Be sure to check.
When it comes to finish we have just discovered that Consumer Reports says that clear finishes don’t work on decks. They tell us that the clear materials just don’t hold up. We always have disliked using paint. Too much maintenance. Consumer Reports Magazine seems to agree. Whatever you choose make sure that your finish coat is oil-based and high quality.