Vinyl Door/window installation question

[brwqb]

When installing new windows/patio doors do you use minimal expanding foam on all four sides? My real question is do you shim up the bottom and use minimal expanding foam or do you lay a caulk bead on the bottom and set the door/window on the caulk bead?

Thanks for any help
Dave

[randy]

On windows, we use minimal expanding foam on all sides, including under the window, around the shims. Anywhere air could penetrate, is a good place to use the foam.

On patio/french doors, where we are setting on a concrete slab, we set the threshold onto multiple lines of caulking only (no foam). Of course we always foam the sides and top.

[brwqb]

Randy my Patio door isn't on a concrete slab, so would you use foam on the bottom also? Thanks

[randy]

If the sill is very flat and level, no. If you have to do a lot of shimming to get the sill level, yes.

Here in Houston, our jobs are always on slabs, so I will defer on this, to the pros here who regularly deal with your situation, however.

[XSleeper]

ideally, doors should be set on top of pan flashings. Problem is, very few places require them, and very few installers like to use them.

At a minimum, I like to install some ice and water shield (a self-sticking membrane- there are several brands) across the bottom of the opening, then out and over the sheathing / building paper to act as a flashing. If the sheathing and building paper are not or cannot be exposed, I'll make an aluminum flashing that will bend down over the siding edge and seal the edges with ice and water shield.

Then as Randy mentioned, I'll run several beads of sealant across the bottom and set the door on that. The idea of the flashing / membrane is to keep the bottom of the rough opening from getting wet at all. Caulking alone may prevent water intrusion but if the area continually gets wet, the caulking (and subfloor) won't last forever. Running a surface bead in front isn't a good solution either, because if water does get in (such as from above), that bead can act like a dam causing water to back up behind it when it can't run out.