Flashing Doors and Windows

Old 01-28-05, 06:58 PM
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Flashing Doors and Windows


Have stripped down the garage doors (4) and also have two entrance doors and a window in a detatched workshop at a house we recently bought.

Am installing fiber cement trim and siding planks.

On the garage doors and windows (overhang on sofitts is 2'), I'm assuming that flashing is the right way to go, although I recently saw on some do-it-yourself show on TV about a "rubber" flashing made by "Grace" that looked real easy to install instead of traditional galvanized or aluminum.

I am also surmising that just adding calk to the joints isn't enough.

Some advice on what is right would be most appreciated.


Deland, FL
Old 01-29-05, 11:12 AM
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The installation instructions at: http://www.jameshardie.com/builder/i...stallation.php are pretty much the standard for all types of fiber cement siding. It is recommended that a weather barrier (tyvek, tarpaper, etc) be used behind the siding. Some areas also require additional moisture flashings behind brickmoulds and nailing fins (be it #30 felt or a self-sealing product such as Moiststop, or Tyvek Flashwrap). Obviously, dripcaps need to be installed on top of everything, and it is important that these dripcaps also be flashed behind the building paper.

It is very important that the caulking you use be paintable and also compatable with your fiber-cement product. The product we use is OSI Quad, which meets all the ANSI-ASTM requirements for fiber-cement applications.

Additionally, cement siding is corrosive to aluminum, so you cannot use bare aluminum flashings (such as your dripcaps). An 1/8" gap around brickmoulds, and between butt joints is usually sufficient to allow for expansion and contraction, and also provides a good gap for your caulking to "grab onto".

I seem to be going on a bit... I hope that somewhere in there I covered the original question. LOL

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