The sealant joints (caulking) applied at the junctions of the various components of your home’s exterior envelope must be inspected regularly—ideally, in the spring and fall. Spend a few minutes taking a close look around all window and door frames, among other joints, to make sure the seals are in good shape.

Repairing joints: sooner rather than later

Defective seals are most often attributable to:

  • use of poor-quality sealant product;
  • improper application; and/or
  • incompatibility of the sealant with the surfaces to which it is applied.

If you notice cracks in the caulk, or it’s coming unstuck, you need to take action. The repair job is quite simple and inexpensive. And you should do it sooner rather than later: a loss of air- or watertightness can lead to high costs. Remember:

  • Water infiltrations will damage your home’s cladding and insulation and even its structure;
  • Air seepage will mean a higher energy bill as well as uncomfortable drafts during the colder months.

Choosing the right sealant

Before you buy a sealant product, carefully read the description and the application instructions. This information is crucial, and will tell you right away if the product is right for your situation.

You need to take the following into account:

  • Compatibility of the product with the surfaces it will be used on. The surfaces the caulk will be applied to (wood, metal, masonry, glass, etc.) determine whether you should choose latex, silicone, an elastomeric sealant, polyurethane, etc.
  • The degree of elasticity or “stretchability” of the sealant. The caulk must stay flexible and stretchable to adhere properly to surfaces, in all weather conditions. In Quebec, given the huge temperature extremes in our climate, this criterion is by far the most important. You should have no problem finding sealants with flexibility and elasticity guaranteed in temperatures as low as -40°C.
  • The product’s other qualities. Ease of application, range of application temperature, drying time, VOC content and toxicity, drying shrinkage coefficient, adhesion, viscosity, colour, resistance to UV radiation, paintability, etc., are all characteristics to be considered.

The cost of the product depends on its quality. A longer-lasting sealant will obviously be more expensive—but the extra investment is well worth it.

Should you apply the sealant yourself? Call a contractor?

If you have fairly good manual dexterity—which is essential for using a caulking gun—and have a sure enough hand to apply a uniform, neat bead of caulk, you may want to apply the product yourself.

In some cases, however, it’s a better idea to have a professional do the job:

  • If there is difficult or extensive prep work;
  • If the product is to be applied high up on the building;
  • If you aren’t particularly skilled at this type of work.

Professionals will normally use high-performance products and have developed sufficient skill to create perfect seals. It may be worth it to spend a few extra dollars to be assured of great results.

Preparing the surfaces: an essential step

Before applying new sealant, you must:

  1. Remove the existing seal. Caulking over an existing seal will likely give unsightly results, because the new seal will be too wide. What’s more, the seal probably won’t be very durable, because the caulk won’t be thick enough. If the old sealant is tar-based, it may be diluted by the solvents in the newer product and “bleed” through. And if it’s silicone-based, applying a different type of product may not guarantee sufficient adhesion.
  2. Properly clean the surfaces. Dust and contaminants can affect sealant adhesion. Choose a cleaning product suitable for the surface and for whatever deposits have accumulated: dirt, wax, grime, oil, mould, etc. Remember to follow the manufacturer’s instructions and allow all surfaces to dry thoroughly before applying the new sealant.

Achieving an effective, durable seal

Durability and performance of sealant joints are directly related to:

  • the width of the surface of contact between the caulk and each element to be covered. The wider the surface, the better the adhesion and the longer the seal will last.
  • the width of the gap to be caulked. If the gap is wider than 6 mm (1/4 in.), insert a backer rod (a length of foam “rope”) first; it will provide an appropriate base for the sealant and keep it from sinking into the gap.
  • compliance with the minimum and maximum seal dimensions, both width- and depth-wise. Check the manufacturer’s specifications; every product has its specific characteristics.

Lastly, if you choose a product with a high solvent content, such as a thermoplastic sealant, don’t smooth the bead (e.g., with your finger) to achieve a better look. Evaporation of the solvents will cause the bead to shrink and perhaps come unstuck.

Though they may not seem like much, sealant joints play a huge role in protecting your home from air and water infiltration and ensuring comfort. For optimum effectiveness and durability, you’re better off choosing a quality product and making sure it is applied according to best practices.

Our thanks to Michel Lussier, technical advisor for Mulco products at PPG Industries, for his contribution to this instalment of Tips & Tricks.