This is good information for homeowners to be aware of - for your own safety and in preparation for selling your property. Decks are very common areas of concern on the home inspection reports that most buyers obtain as a condition of the purchase contract. These issues, if severe enough, can jeopardize a sale all together or seriously affect your bottom line because these problems are often perceived as huge and costly to the average buyer, prompting demands for large concessions. Addressing the issues prior to listing your home allows you the time to properly plan and evaluate the costs of correction in order to make sound decisions in the negotiation process. Even if you don't actually DO the work ahead of time, having professional advice and estimates are in your best interest. - L
From the Desk of:
Richard A Hetzel
Architect (NY) & Home Designer (PA)
Well, let’s put it this way…much construction in the Poconos older than a few years is not the best, and decks may top the list of substandard construction. Those buildings and decks were built when there was no particular building code, and inspection quality varied considerably. The adoption of the Pennsylvania statewide building code in 2004, and the training of building officials have brought welcome change in quality and enforcement. Let’s look at some of the common problems of older decks.
COMPARE YOUR DECK TO CURRENT CODE
Starting with the ground, we find many decks which are not built on foundations which extend below the frost line, generally required to be 3 feet 6 inches below the surface. Such construction risks frost heave, as such decks are commonly built on concrete blocks lying on the surface.
While we’re down there, look at the bottoms of the deck posts. They should be anchored by galvanized steel or cast aluminum post bases which keep the end of the wood post from contacting the concrete foundation. The post bases should have an anchor bolt which extends into the concrete.
Moving up a little, the posts themselves are often 4x4 wood, but if the deck is a full story above the ground, 6x6 posts are a better choice.
Then we move up to the girders that support all the deck joists. There is no way to suggest what these girders should be made up of, because it depends on the exact design loads they are carrying. The problems in this area arise because many decks were just thrown up by carpenters who simply guessed at the girder requirements. We frequently see girders with very visible sag or deflection, which may indicate that they are inadequate for the loads.
Deck joists may or may not be undersized, and again, we would have to see the specific deck to evaluate them. Current building codes require that the joists be attached to the girders using “hurricane clips”, inexpensive galvanized steel plates which prevent uplift of the deck in high winds. These were not required on older decks (pre-2004), but are very easy to install on an existing deck.
If your existing deck does not conform to current codes, you cannot be required to update it, unless it was recently built without a permit, when a permit was required. However, if it has any of the deficiencies described, you may elect to improve it to the extent you feel will be safe and reasonable. Additionally, keep in mind that if you are adding to, or roofing over, or doing any other major changes to your deck, you may be required to bring the entire deck up to current code standards, including footings and foundations.
BUILDING MATERIALS MATTER
All the wood used so far in our deck should be pressure treated with preservative, or woods with natural decay resistance such as cedar or redwood. Older deck lumber was treated primarily with Chromated Copper Arsenate (CCA), but this chemical has been phased out for residential use in favor of Alkaline Copper Quat (ACQ). Fasteners used with ACQ must be hot dip galvanized or stainless steel to prevent corrosion.
The decking itself (the “floor”) can be any of several products. Older lower-quality decks have floors of pressure-treated lumber. Better decks have cedar floors, and exquisitely expensive decks can have floors of teak or other exotic woods. There are also several synthetic deck floor products on the market, most made of a combination of recycled plastics and wood fibers.
Surrounding the deck is a railing, which, since 2004, is required to have no space greater than 4 inches in width. Many older decks have simple two-rail railings which would not meet current codes. You are generally not required to upgrade older decks to new code requirements, but you may consider it, especially if you have very small children. Railings can be made of pressure-treated wood, or naturally decay-resistant wood, vinyl, or exotic items like glass or plastic-sheathed cable. Railings should be 36 inches high.
The place where the deck connects to the house is another potential trouble spot. Usually a board is fastened to the house, and the deck joists connect to the board. Very old decks might have a small ledger strip, such as a 2x2 nailed to the board on the house, and the joists rest on the ledger strip. Newer decks connect the joists to the board with galvanized steel joist hangers. The board itself should be lag-screwed into the house structure, with ½-inch diameter bolts not more than 32 inches on centers. Existing decks can easily and inexpensively be retrofitted with both lag-screws and joist hangers, if they do not exist.
Finally, there should be metal flashing with extends up behind the siding, and out over the top of the attachment board. Many older decks do not have this flashing, but it can be added with moderate expense.
CODE COMPLIANCE = SAFETY
There are many stories of deck collapses, some with tragic consequences, and most could have been avoided with careful inspection and upgrading. Older decks should be checked for the presence of the features described, and missing elements added if possible. It’s easy to add most of the features, and doing so will improve the safety and longevity of your deck, and you won’t have to “haul the deck” to the garbage dump.
Here’s an excellent link to a good compilation of building code requirements for residential decks. Building codes change every three years, and the current code may differ somewhat from the linked document, but it won’t be by much.