simple question on caulking around a window
Where to put the caulk? This is our little 12×16 off grid mountain escape cabin project that’s now in its third year, and we’re finally to the point of installing the exterior siding. Each window was first framed with 4/4 Hardi trim, the the Hardi-plank lap siding butts up to the trim, with a 1/8″ space for caulk between the lap siding and the window trim. The Hardi installation guide makes it very plain to not caulk between the lap siding and the top trim piece, where there is metal flashing, but what about the bottom? Considering how the window flashing and house wrap are integrated, it makes sense to me to seal here, but I don’t find any explicit instructions. Maybe it’s supposed to be obvious.
Also, what about between the aluminum window frame and the exterior trim? Again, this seems to be a perfect point for water to get in behind the siding, but I ask because on our house the builders did not caulk in there. And on the side of the house that gets exposed to wind driven rain we do have some damaged siding that I’m attributing to water getting in here. Is there any reason not to caulk here? Would one caulk all sides, or leave it off the bottom?
Your help and expertise is very much appreciated.
Replies
I would not caulk the bottom. You want a place for any water that get in to be able to weep out. As far as the siding to trim most times it gets done, but it's not east to say in your case unless you provide the full detail, such as flashings/vapor/ barrier tar paper etc.
I'll try to provide as much detail as my memory will allow
thanks for the reply. Here's how the windows are mounted: first Tyvek house wrap, then I flashed the rought opening using leftover Grace Ultra roof underlayment in place of flashing tape following the technique outlined for door openings in FH April/May 2011 pp 58-63. The window was set into place with caulk under the nailing flange on the top and sides, but not the bottom. After nailing, more flashing tape was applied over the nail flange and sealed to the tyvek on top and sides, but not the bottom. Then the exterior trim was applied around the window frame, then the lap siding butts (almost) to the trim.
James Hardie is very clear about caulking between the siding and the trim on the top (don't do it) and the sides (yes, do it) but they don't mention the bottom. It seems to me that with wind driven rain, water hitting the window will roll down over the bottom trim piece, and with no caulk between that trim and the siding it will wick into that space and wind up behing the siding that is under the window. There it will follow the tyvek on down. Would it not be better to seal that space and prevent the water from getting in there in the first place? Same question for the space between the window and the trim. Any water getting into that space will be stopped by the integrated nailing flange, but then it has no place to go but down between the house wrap and the siding. Maybe that's considered to not be a problem with the use of house wrap, but in the case of my non-wrapped house it's made a mess that will have to be cleaned up some time. Luckily I live in a place that doesn't get very much rain.
Any guidance is appreciated. Me trying to rely on what makes sense to me at the moment may have unforseen consequences.
Sounds to me like a well thought out system. Dont second guess yourself caulk it all up. Anything getting behind the caulk (should be nothing if you do a good job) is going to hit the the Tyvek or Grace and and not get anywhere near the sheathing or interior.
I tried RTFM
which means "read the ***** manual"; I dug out the installation instructions for the Andersen windows which I had used when putting in the windows (a year ago) but had forgotten about. It clearly states to caulk all sides around the window between exterior frame and the trim. So between Andersen and Hardie I think I'm set. Thanks for the help.