Moisture and Other Problems
Wood decks and balconies are either cantilevered (that is, built on floor framing that extends from the wall) or attached to the side of the building. If attached to the wall, the joint is the source of most problems. If not properly flashed, moisture gets in and rot develops. If cantilevered, the actual penetration through the wall must be sealed properly or moisture will enter there.
Once moisture enters the framing, rot may develop in the deck. It may also develop in the floor and wall framing, requiring expensive and disruptive repairs. Cantilevered decks can be a “magnet” for rot being drawn back into the building.
Concrete decks are almost always cantilevered extensions of the floor slab. Moisture may enter the concrete through cracks, or simply penetrate the surface if the concrete is not maintained or water is allowed to sit long enough.
Water entering the concrete may cause spalling whereby portions of the concrete actually break off. This occurs when the rebar (reinforcing rods in the concrete) rust and expand, popping off pieces. In cold climates, the freeze/thaw cycle may also cause the balcony to break up. Once in the concrete, moisture may also migrate to other structural components within the building.
Other sources of moisture for both types of decks are penetrations made to hold railings and other appurtenances, improper slope allowing for standing water, or failure to permit water to run off either to drains or through the open framework of the deck. In concrete decks, railing installations that use a sleeve drilled vertically into the concrete to hold the base are particularly vulnerable.
Often, decks and balconies are located to take advantage of views, which may also expose them to more severe weather and driving rain. That is why the flashing and caulking around doors and windows is also very important.
In addition to damage and deterioration caused by weather which could lead to a catastrophic kind of failure, one must also pay attention to the more obvious safety precautions like the condition of the railing. The railing must be securely mounted to the wall or building. It must be in good condition.
In recent years, the code has changed with regard to the spacing between balusters. Today, there must be no more than a 4 inch gap where previously, 6 inches was allowed. Some parts of the region have grandfathered older railings, but others do not.
Periodic inspections and preventive maintenance can help avoid or mitigate most problems. The following checklist was prepared to help you and your association avoid some of the more serious deck and balcony related problems.
For Existing Wood Decks
¨ Check the joint between the deck and the house at least annually. Ideally, there should be a space between the deck structure and the building to prevent moisture and debris accumulation that will lead to rot.
¨ Annuall, 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.
¨ Every two to three years, the entire deck should be stained or painted, top and bottom. This is equally true if the deck is made of pressure treated (rot resistant) lumber.
¨ Annually, check the base of any support posts that are close to the ground for rot.
For Existing Concrete Decks
¨ About once a year, after a good rain, check to see if there are any cracks or if there is any ponding of water on the deck. Seal all cracks and if ponding occurs, investigate filling and recontouring the deck.
¨ Apply a concrete sealer to the surface of the deck or apply a waterproof coating to the surface. Do this at least every other year.
¨ Check all drains and/or scuppers quarterly to be sure they are clear and running freely.
For All Decks
¨ 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.
¨ If the railing has any opening through it larger than approximately four inches square, additional screening is recommended to minimize the risk of young children crawling through the railing.
¨ 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.
A Few Final Words
When building or rebuilding wooden decks, we recommend the use of pressure treated lumber. We do not, however, recommend pressure treated lumber for the actual deck material or the railings where there is a chance of splinters, especially for young children. The compounds used in pressure treating the lumber have been known to cause skin irritations. 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.
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 decks.
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 adequately.
And lastly, if you suspect a problem, it is wise to consult a licensed professional engineer. Many times, only the symptom is treated while the real problem goes unnoticed. Someone who thoroughly understands building systems and details will be able to help determine the cause of the problem and recommend a cure before the problem becomes too severe.