I will be building addition for my old house and replacing siding. I
am leaning towards fiber cement or cedar siding. My house currently
has no house wrap. I want to install exterior foam insulation boards
over entire house and new addition. I have a couple of questions.
1. Since exterior foam insulation boards are 1" to 2" thick what to do
with windows? How to make them flush taking into account increased
wall thickness due to insulation? Right now they are flush with
2. Can someone point me to info regarding what goes over what: house
wrap, insulation, rain screen and finally siding?
Build up with boards thicker than final surface of new siding.
House wrap, thin foam panels, vinyl siding, done. Windows and door
openings flashed as recommended after house wrap. Go poke around some
new construction sites after working hours and view what the
journeymen are doing. Don't overcomplicate your own project.
There is usually a stand off between window edges and exterior surfaces -
meaning that you build up the window edgeing and then trim it. If this is
the trim that you will paint you would buy brick mould. If you are going to
wrap the trim in aluminum just custom mill the needed stock yourself and
save the cost of moulding. Who cares what's under the aluminum.
The current issue of Journal of Light Construction (Nov 2009) has a
good article on Retrofitting Exterior Insulation.
If you are thinking of replacing your windows at some point, this
would be a good time. You could decide to set the new windows flush
with the outside and add internal jamb extensions, or flush with
inside and add exterior jamb extensions. If your windows are OK, then
you will have to add exterior jamb extensions (and head and sill
extensions) to make up for the foam thickness. You'll want to flash
the jamb extensions. Make sure to maintain the sill slope with the
Put the house wrap on first, then the foam, taping all the joints with
the proper tape. It would be ideal to use two layers of 1" foam
staggering the joints, but that's more work and will cost more than 1
layer of 2". Then put vertical nailers for the siding, screwing them
into studs with long screws. The foam will serve nicely as the rain
screen. Fiber cement is heavy, so secure the nailers well.
Along the bottom edge, put a strip of ridge vent material (the woven
plastic kind) wrapped with window screen material. This will block off
the space behind the first course of siding while allowing water out
and keeping critters and insects out.
Thank you for thr info. I replaced windows a couple of years ago. They
are top quality casement windows installed now flushed with sheeting.
I don't want to rip and re-install them.
I assume by "vertical nailers" you mean wood strips to nail siding to?
How thick are hey to be? What material are they made of? If they are
fur or other wood can they rotten with time?
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