Which practice is required when using foam in exterior assemblies to prevent leaks?

Which practice is required when using foam in exterior assemblies to prevent leaks?

• A. Joints must be sealed to ensure no leaks or tongue and groove
• B. Joints must be left unsealed
• C. Install an additional waterproof membrane
• D. Paint the foam for UV protection

Answer: (A)

Sealing the joints in exterior foam assemblies is essential because foam boards alone don’t form a continuous water barrier. Any seam—whether a simple butt joint or a tongue-and-groove connection—can become a leak path if it isn’t sealed. Applying a compatible sealant or tape to all joints creates a continuous moisture barrier that prevents leaks and also helps maintain the insulation’s effectiveness. Leaving joints unsealed allows moisture to penetrate. Adding a waterproof membrane can be part of some designs, but it doesn’t replace the need to seal the joints, and painting the foam only protects against UV exposure, not water intrusion.

Sealing the joints in exterior foam assemblies is essential because foam boards alone don’t form a continuous water barrier. Any seam—whether a simple butt joint or a tongue-and-groove connection—can become a leak path if it isn’t sealed. Applying a compatible sealant or tape to all joints creates a continuous moisture barrier that prevents leaks and also helps maintain the insulation’s effectiveness. Leaving joints unsealed allows moisture to penetrate. Adding a waterproof membrane can be part of some designs, but it doesn’t replace the need to seal the joints, and painting the foam only protects against UV exposure, not water intrusion.