Deck Caulking Advice and Tips - Using Sikaflex 290 DC

Deck Caulking Advice and Tips:

Using perhaps the best Deck Caulk on the market today Sikaflex 290 DC we will give a quick overview of "best practice" when installing the deck caulking compound.


Depending on the deck's design and construction, a large amount of movement might take place. When applied correctly, Sikaflex 290 DC will contain a total movement factor of 10% of the average joint width (1mm of movement / 10mm of joint width). This movement factor must be taken into consideration at the start of the job. With bare timber, expansion and contraction occurs less due to thermal changes, but more due to variations in the moisture content in the wood itself.

The design of the joint must also take into consideration the movement of the sub deck.

Dry or seasoned teak or other timber must have a moisture content of less than 12%. In service, a bare timber boat deck can typically vary in moisture content between 5% and 20%.

"Considerable difficulties arise when timbers used in deck construction are not completely seasoned or dried."

When Sikaflex is used, the timber should ideally be at least 6mm thick to avoid the curling at the edges that occur due to heat and moisture. To prevent this effect, the entire width of the primed planks should be thoroughly bonded down with Sikaflex 298.

Application of Sikaflex 290 DC Deck Caulking Compound:


  • Before any wok commences, ensure that the temperature of the wood does not exceed +30C.
  • In addition the ambient temperature during application should be constant or falling and ideally within the range of +5C and +35C.
  • Apply Sikaflex 290 DC ensuring that air is prevented from entering the seam by placing the tip of the nozzle against the bottom of the joint and keeping the gun at an angle of 60-90 Degrees.
  • If narrow joints need to be caulk, a specially designed nozzle may be required.
  • Continue to apply along the seam, so that the joint appears to slightly overfill behind the nozzle, but maintain a constant motion.
  • After applying Sikaflex 290 DC but before skinning occurs, compress the excess material onto the surface of the deck using a slightly flexible spatula at an angle of 45 degrees. This produces a convex appearance of the joint and fills the seam completely.
  • Protect the joints from rain and direct sunlight prior, during and after caulking for a period of at least eight hours.
  • Do not use excess material from the spatula for filling seams as the skin already formed will prevent proper adhesion and will leak!
  • Sikaflex 290 DC is ready for sanding.