Question on using foam sealant (new windows)

[Tidybuoy]

I installed new windows on half of the house last weekend. 2 of the windows are different from the rest of the house as that area has a brick wall. After normal installation of the windows, there is a special trim piece on the outside ("Brickmold") which I am replacing since it is very weathered and peeling paint and it's easier to replace than sand.

When the brickmold is removed, it exposes a large gap and I'm wondering if I should fill with foam sealant. The gap does not have any affect on the sealing of the window as they are sealed in a frame that is sealed to the wood frame of the house. The brick is installed onto the house frame but leaves this gap (see photos).

I tried filling with "large gap sealant" and it seams that it just sprays forever without really filling up anything. Should I continue filling with foam or use fiberglass insulation or do nothing and just replace the molding.

Looking for advice.







You can see that the brickmold will eventually cover up this gap.

[dad911]

Either spray foam for windows (does not expand too much) or Foam backer and caulk.

Do yourself a favor and use PVC brick molding. Wood against masonry is bad. If you really need to use wood, tape the backside with this butyl protecto wrap or equivalent, so the wood can't touch brick.

[drkshdw]

Stuff the cavity with fiberglass first to fill the big gaps and then the spray foam to seal it up. Then the brickmold and then caulking.

[mfiazzo]

Agree with PVC molding also agree with fiberglass then window foam. Other foam expands too much and may impede window operation.

[KFC911]

Originally Posted by drkshdw

Stuff the cavity with fiberglass first to fill the big gaps and then the spray foam to seal it up. Then the brickmold and then caulking.

^^^ yep...

[Tidybuoy]

Thanks! Fiberglass insulation, then foam sounds like a good idea.

[cabmandone]

I wouldn't go with fiberglass unless you're sure you can get it sealed, that stuff will hold water forever! I'd go with the Great Stuff window and door expanding foam. It's a minimal expanding foam so it doesn't put pressure on the window. Be careful though as it does expand out which can be messy.
This stuff
Great Stuff Window & Door Foam Sealant 12 Oz. 175437

[John Rogers]

Where did you get the windows? If they came from a window supplier that also does installations they could tell you the best was to go I did vinyl windows over our very old aluminum framed ones. The manager told me how to seal the outer flange against our vinyl siding with a special type of sealer, which took about two tubes per window!

[cabmandone]

Just a suggestion but you might consider vinyl brick molding If you haven't already purchased all the wood brick molding.

[flatbutt]

Originally Posted by mfiazzo

Agree with PVC molding also agree with fiberglass then window foam. Other foam expands too much and may impede window operation.

Boy and howdy! AMHIK

[javadog]

If there is a void back there of considerable size, that we can't see in the photos, you might consider using backer rod in front of the void, then foaming the rest. If the entire void is as narrow as what is seen on the outside, then just foam should be sufficient. I would caulk the joint too.

[MRM]

I spent about 15 years representing the largest window manufacturer in the country. You need to fill the void with low expansion closed cell foam. Great Stuff window foam with a small nozzle to get into the cracks and entirely fill the void is what you want. The foam has to fully fill the void so that water can’t enter but it can’t expand because it would impinge on the window frame if it did. The foam also needs to be closed cell so it doesn’t absorb water.

Get the right Great Stuff product and shoot the void until it’s full. Let it sit and expand and dry and then cut the excess away. Don’t bother with Fiberglas.

You do have to caulk the joint. That is essential. Use backer rod and caulk to seal the exterior joint and prevent water entry. Just caulk alone won’t seal the joint even though it looks like it will.

[onewhippedpuppy]

One other tip, I would mask the window and brick adjacent to the void before you foam. Once it expands out the foam can make a mess, and it sucks to clean up. If you mask you can let it expand out, dry, then easily shave it to flush with a utility knife.