How To Seal Cornerboards CLICK TO PRINT

Once you have identified gaps in your cornerboards (the vertical board that covers where the ends of the siding meet on the corner of your home) use these directions to seal them up. Be sure to check for application temperature ranges on products and if rain is forecasted to occur during the dry time of your selected product.

Latex sealant:

Easy to apply and clean up, latex sealant can be used to seal up small air leaks and gaps. If the gap is greater than ½" in width, use a foam backer rod first, then apply the sealant over the backer rod.

  • Be sure to read the entire package to ensure you have all materials the job will require and to budget for dry times in your project. Carefully review all safety precautions on the package.
  • Clean and dry the surface you will be sealing to ensure it is free of all dirt, dust, grease, old sealant and debris. (To remove old sealant, carefully use a utility knife or a caulk removal tool. Once completely removed, wipe away any debris. Use a rag to wipe the joint surface with rubbing alcohol or an over-the-counter disinfecting spray, rinse thoroughly with water, and dry.)
  • Apply the painters tape to mask off areas around the joint where the sealant should not appear and to help give a straight sealant line.
  • There are many different nozzle designs on sealant cartridges. Read the instructions of your select product for how to cut the nozzle. Some nozzles have an inner foil seal that will need to be punctured.
  • Load the cartridge into the caulking gun. Applying steady pressure to the trigger, fill the gap down the length of the cornerboard with an even bead of sealant. It is best to push the sealant ahead of the nozzle to ensure that it gets into the joint for a proper seal.
  • If you applied painters tape, remove the tape prior to the sealant skinning over. To correctly remove tape, lift the edge up at a 45° angle away from you, and carefully place in a trashcan.
  • Wipe away excess sealant with water and a damp cloth before the sealant dries. Excess dried sealant will need to be cut or scraped away.

Silicone sealant:

The application of silicone sealants is very similar to latex sealants. Two notable exceptions are that silicones must be cleaned up with solvent cleaners, not water. And, most silicones are not paintable. Read label instructions carefully.