Annually, check the joint between the deck and the house. Ideally, there should be a space between the deck structure and the house to prevent moisture and debris accumulation that will lead to rot. Without that, rot can occur easily. Regular inspections will help identify problems before they become serious. If necessary, the decking should be removed in the first four to six inches along the building to inspect the condition of both the deck framing and the building framing for possible rot. It's not uncommon to find rot in this location in decks as young as five to ten years old.

Annually, go under the deck and inspect the top of the joists (horizontal framing members) supporting the decking. This is where rot will often start. Using an awl, screwdriver or knife to poke into the upper one to two inches of each joist will help identify problems in their early stages and allow correction before major repairs are required.

Annually, check the attachment of the railing. Grab the railing at the top and shake it vigorously. If there is any looseness, the railing should be more solidly attached for your safety.

Every two to three years, the entire deck should be stained or painted. This is equally true if the deck is made of pressure treated (rot resistant) lumber.

Use of pressure treated lumber is not a substitute for good construction techniques. All of the same annual inspections and proper maintenance are applicable even if the deck is constructed using pressure treated lumber.

Annually, check the base of any support posts that are close to the ground for rot. Using an awl, knife or screwdriver, poke into the wood. If significant rot is found, repairs should be undertaken before serious problems develop.

If the railing has any opening through it (below the top rail) larger than approximately six inches square, additional screening is recommended to minimize the risk of young children crawling through the railing and falling to the ground below.

The height of the railing is recommended to be at least 36 to 42 inches. Lower than that does not provide a safe enclosure for adults or children.

For New Decks

The use of pressure treated lumber is suggested for all framing members. We do not, however, recommend pressure treated lumber for the actual deck material or the railings where there is a chance of splinters. The compounds used in pressure treating the lumber have been known to cause blood poisoning. Rot resistant woods such as Cedar, Fir or Southern Yellow Pine can be used for the railing and the deck surface. With proper maintenance, the life of this material will often be as long as that of pressure treated material.

Make sure the deck is spaced at least two inches out from the building to which it is attached. There are various devices available for this purpose. Recently, one Maine firm has begun manufacturing what they call the Maine Deck Bracket specifically for the purpose of separating the deck from the building while still providing needed support.

Railings should be 42 inches high and solidly mounted. We do not recommend railings that incorporate benches since they encourage unsafe activity such as sitting on the top rail.

Support posts should be supported on concrete sonotubes founded sufficiently deep in the soil to prevent frost action. Also, the bottom of the wood posts should be separated by one to two inches from the top of the concrete or any adjacent soil to minimize the risk of rot.

Diagonal bracing should be used in conjunction with all support posts to provide additional stiffness for the deck itself.

Other Deck Observations

When looking at existing buildings, pay particular attention to cantilevered decks; those that extend out from a building with no other exterior support. Depending on the age of the building and the quality with which these decks were originally built, they can be a "magnet" for rot being drawn back into the building along the cantilevered framing members that extend out from within the building framing itself. These decks deserve extra special inspection on any home more than five to ten years old.

Any decks associated with waterfront properties deserve closer inspection than those related to inland properties. The added exposure of a waterfront location will take its toll rapidly on exterior wooden decks.

Any stairs providing access to exterior decks should be equipped with railings. These stairs should also meet all other normal stair construction requirements, including uniform tread width and riser height. A suggested rule of thumb would be to have treads eleven inches wide and risers seven inches high to provide a comfortable, safe stairway.

In general, the space underneath a deck should not be enclosed. It is better to leave the deck wide open so that it can breathe properly.

Decks are an enjoyable part of many homes. With the cooperation of the insect population, many carefree, relaxed hours can be spent on a deck. Decks require far more maintenance than most other building components, however, due to their typical construction methods and their extreme exposure to the weather.

Be sure to check your deck regularly and, when necessary, perform proper and regular maintenance.

Criterium Engineers, Copyright © 1999

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