ᐅ Sealing windows at the bottom with compressible sealing tape: How to ensure vertical load transfer?

Hello everyone,

I will soon be installing a few windows with window sill connection profiles into wooden reveals, and I am currently wondering about the best way to design the vertical load transfer.

For the lateral sealing, I am using a 3-zone compressible sealing tape matching the width of my windows, and below, from the same system, a 3-zone compressible sealing tape for window sill connection profiles matching the depth of the connection profile. The issue, however, does not only concern window sill profiles, but generally the use of compressible sealing tape with support blocks.

Ideas:

• Place support blocks only on the interior side: (Suboptimal load transfer only at the inner edge)
• Place support blocks in the middle and interrupt/cut out the compressible sealing tape (Does the sealing tape still seal well in this case?)
• Install a support bracket or interior window sill (Again, load transfer only on the inside and it interferes with the sealing tape inside)
• Mount with angle brackets (I am not sure if this is a good idea. It also interferes with the sealing tapes and exterior window sill)

What is generally considered the best practice for this?

Hello :-)

The compressible sealing tape at the bottom area has not proven effective under load-bearing conditions.

Support blocks should be properly sized. In your case, they should be installed under the window sill connection. The advantage is that they will no longer interfere with any additional waterproofing.

As you already mentioned, sealing with compressible tape can be done on the left, right, and top parts of the window, while the bottom can be sealed with a membrane toward the masonry, both on the interior and exterior.

The joint between the compressible tape and the support blocks will not provide a reliable seal because there will always be a gap at the joint.

Best regards

Daniel

My father-in-law has been a window installer for 30 years. Just as @montageprofis describes, he installed the windows of my future neighbor two weeks ago.

It was worth a try.

I cut centered recesses into the tape (45mm wide) and placed supporting blocks (24x100mm) there. That worked well and would have been completely airtight, since both sides were sealed. BUT

The compressible tape expanded so quickly (not just at the bottom but everywhere) that 10 minutes later I could barely fit the window in (even though there was a 2cm (0.8 inch) gap).

Then I couldn’t push in additional supporting blocks as planned, because the tape sealed so tightly.

How can the expansion of these tapes be slowed down?

Freezing?

Yes. Or at least cool it in the refrigerator.
Alternatively, use ice spray on it.