This picture window install has 5/4 Boral flush window trim at the sill rather than a traditional extended sloped sill with drip kerf. What is the preferred method for preventing water from wicking back towards house? I see jobs where the trim is just caulked to the siding but that seems subject to failure.
Somehow cut a drip kerf into existing bottom edge? Metal flashing tucked up under trim boards with turned down drip edge flush with wood edge? Can some caulking be avoided to allow for sill pan drainage?
Replies
To prevent water from wicking back towards the house in a picture window installation with 5/4 Boral flush window trim at the sill, instead of a traditional extended sloped sill with drip kerf, you can consider the following methods:
Drip Kerf Addition: If feasible, cutting a drip kerf into the existing bottom edge of the trim can be effective. This kerf acts as a barrier, directing water away from the house. However, this approach requires precision and understanding of the material properties to avoid damage.
Metal Flashing: Installing metal flashing under the trim boards is a commonly used method. The flashing should have a turned-down drip edge that is flush with the wood edge. This helps in directing water away from the window and the house. Ensure that the flashing extends beyond the trim and is properly sealed at the top.
Caulking: While caulking is commonly used, relying solely on it for water prevention can indeed be subject to failure, especially over time as the caulk ages and potentially cracks. If caulking is used, it should be high-quality, exterior-grade, and applied meticulously to prevent water ingress. It's advisable to inspect and replace caulking as part of regular maintenance.
Sill Pan Drainage: If you're using a sill pan, it's important to ensure proper drainage. This may involve strategic placement of caulking to allow for water to escape while preventing it from entering the building envelope. Leave weep holes or a similar drainage pathway to allow any water that does get in to escape.
Regular Maintenance: Regardless of the method used, regular inspection and maintenance are key to ensuring the long-term effectiveness of any water prevention strategy. This includes checking for any gaps, cracks, or wear in the materials used and addressing them promptly.
Professional Consultation: Given the critical nature of proper water management in window installations, consulting with a professional or the window/trim manufacturer for specific recommendations based on your exact situation and the materials used can be very beneficial.
Hope so it will work for you.
Hey there,
This is a super typical detail we see now with many more modern/simple exteriors being done. We typically will rabbet the sill to receive the siding, providing a "siding tuck" with no need for sealants. As it is shown, and depending on what the siding material will be, you will likely be relying on sealant to keep water out. This is fine as long as the siding material does not come proud of the trim (i.e. cedar shingles will build out to about an inch) so you can get a good caulk joint that bridges the trim and siding joint. Hopefully, the house was built in such a way that the siding and trim are more "cosmetic" than a weather barrier.. As we build now, detailing should be such that the house can tolerate occasional wetting of the drainage plane.. As the other poster noted, sealants should be checked and maintained as part of routine home - work.