Constant exposure to moisture and heat causes wood deck boards to crack, and small or hairline cracks are an unavoidable consequence of your deck's aging process. The wood gets wet, soaks up the water, expands and then drys out, contracting and shrinking, causing cracks in the surface of the wood. Repairing the cracks and sealing the wood every two years is a sound alternative to replacing the entire deck. The cost of the repairs to the wood in your deck is minor when you consider the safety of yourself and your family.
To Repair Cracks Under 4 Inches in Length
Fill a plastic garden sprayer with deck wash and brightener and spray the entire deck with the cleanser.
Scrub the deck with a steady pressure applied to a push broom against the wood decking. Allow the cleanser to work at removing the accumulated dirt, stains and discolorations for 15 minutes.
Spray the entire deck with the spray from your garden hose to remove the chemicals in the cleanser from the boards.
With a putty knife, fill any cracks in the wood that are under 4 inches in length with a latex wood filler that is formulated for outdoor application and will not shrink, crack or flake when exposed to rain and sun.
Allow the deck to dry completely.
Fill the sprayer with deck sealer and apply a coat of sealer to the entire deck. This will reduce the rate that the wood absorbs water, which causes the expansion and contraction that causes cracks. Allow the sealer to dry completely before replacing the patio furniture and using it.
To Repair Cracks Over 4 Inches in Length
Place the prongs of a nail puller beneath the head of the nails holding the board in place, and apply pressure to the other end of the nail puller to pull them out.
Lift the entire length of the board with the cracked section from the deck joists.
Secure a new piece of wood that has been cut to length to the joists with 2-inch wood screws at all of the joists. Alternatively, if the underside of the old board is in good condition, you can simply flip it over and reattach it.
Clean and seal the deck as described above.