Caulking FAQs

Should I replace all caulking or just the areas where leaks are occurring?

We understand that keeping your tenants happy is of the utmost importance. If a tenant has a leaky window, you may not have time to do a full system replacement. PCM offers both services and would be more than happy to work with you to decide which solution is the best fit for your particular building and tenants.

When is the building ready to be re-caulked?

Silicone and polyurethane are both successful at keeping water at bay, however, the two sealants can have different lifespans. Assuming proper design and installation, a polyurethane joint’s lifespan is typically 5-10 years. A silicone joint’s lifespan is typically 20+ years. PCM Building Exterior Services division will provide a façade survey to inspect the age and effectiveness of the existing caulk and provide you with a report. In this report, we will tell you the current condition of the caulk and make recommendations for replacement if needed.

What is the difference between “Wet-Glazing” and “Window Caulking”?

  • “Window Caulking” refers to the perimeter joint where the window frame meets the substrate. This joint prevents water from entering the building and protects the window frame from corrosion. It will also prevent drafts.
  • “Wet Glazing” is the process of cutting the rubber seals flush with the frame and installing a 100% silicone caulk to seal the glass where the glass meets the metal window frame (mullions). As the original rubber seals age and weather, they shrink. This causes water leaks, air leaks and will sometimes cause the glass to shift in its frame. It is important to keep these seals closed even if you are not experiencing leaks. Water infiltration into the window frame system will cause corrosion of the frame over time.

Should I use polyurethane or silicone?

While a polyurethane joint’s lifespan is typically 5-10 years, a silicone joint’s lifespan is typically 20+ years. A silicone joint’s lifespan is longer because, chemically, it won’t break down. Silicone is better suited for temperature extremes. Changes in temperature cause the joints to expand and contract. Silicone allows for greater movement. For a full system replacement, most manufacturers of polyurethane offer a 5-year warranty and most silicone manufacturers will offer a 20-year warranty.

  • When deciding between a polyurethane or silicone sealant on a replacement project, you should remember to take a few factors into account.
    • First is the cost of material. Silicone can be up to twice as expensive as polyurethane.
    • Second is the cost of labor. While the initial application process takes about the same amount of time for each material, the frequency at which you will have to repair and replace the polyurethane sealant can be much higher.

Why is it important to remove old caulk before applying new?

All caulk, whether silicone or polyurethane, requires the old caulk to be removed completely prior to installation. Simply placing new caulk on top of old caulk automatically voids all warranties. The new caulk will not adhere to the existing caulk under any circumstances. Polyurethane caulk is an organic material and decomposes over time. Placing new polyurethane over old will cause the new caulk to decompose at the same stage and rate of the old caulk. Placing silicone over polyurethane will cause the silicone to peel off the building. The oils from the polyurethane interact like vinegar and oil. At PCM we also remove all the old caulk and backer rod as part of our full-system replacement.

Should I require the contractor to involve the manufacturer rep?

Definitely. He or she will perform a pull test for the warranty and make recommendations about which primers to use and which caulk is best for the specific application. All buildings are not created equal. Having the manufacturer reps involved guarantees the caulk and installation will be warrantied.

What are the best temperatures/time of year to do this type of work?

Weather Affects Performance; It is crucial to pay attention to the weather, as it can affect:

  • joint size at the time of caulking;
  • contaminants on the surfaces of the joint (like dust, pollen, etc.);
  • the ability for the caulk to “wet” the surfaces of the joint for good adhesion; and
  • proper curing and developing of ideal physical properties.

Ideal Weather Conditions: Dry weather and outdoor temperatures between 50°F and rising and 90°F and falling. Why dry? Low humidity is key during application in order to prevent cracks from swelling with moisture.