Saturday, November 29, 2008

Getting Ready To Install The Windows

I've started preparing to install the windows in the dining room. Before the windows can be installed, the window openings must be flashed (i.e. protected from water). Most windows today are flashed with a peel & stick membrane. The type I've chosen to use is called Blueskin.

At the bottom of the window opening I'm creating a sill pan. A sill pan is designed to catch any water that might somehow leak into the window opening after the window has been installed, and direct that water to the outside of the house. The base of the sill pan is made from a piece of bevelled cedar siding that gets nailed to the bottom of the window opening so that the slope runs towards the outside of the wall.

Once the sill pan is in place, its ready for the flashing. Although the Blueskin has a sticky backing, it will adhere better to a primed surface, particulary in colder weather. I've primed the bottom of the window opening and the first few inches of the outside of the ICF with Blueskin primer that's made specifically for use in cold weather.

Once the primer has dried, the flashing is applied on top of the sill pan and up the sides of the window opening, as well as over the front edge and down the front of the wall.


  1. A question: Did you know any of this stuff when you started? Are you learning as you go, or did you need to learn how to build a house at once, before you started?

  2. Oh, this is Brian.

  3. Hey Brian... I knew most of it from a high level before I started. For some of the details, I'm just learning as I go.

    For instance, with the window flashing... I knew it had to be done; but it wasn't until I started studying it that I found out that you have to install the bottom piece first, then the sides, then the top. That ensures that each higher layer overlaps each lower layer, and sheds the water properly.

  4. To be more precise, that last piece over the top should go on after the window is in the rough opening. That way it covers the top tab of the window and seals it.

  5. Thanks Gene. Yes... very important. Once I have the windows installed, I'll be running another layer of flashing around and over top the nailing flanges.

  6. Thanks for the details on this flashing. We'll be installing windows and doors on our ICF house in the next month or so and this is as good an explanation as I've found. Three questions:
    1. What primer coating did you use under the flashing? We don't have the cold weather issue right now.
    2. Will you be flashing the doors in a similar manner?
    3. How do you plan to finish our your windows inside? With the beveled sill under the window I assume you're going to trim out the window with some similar material?

    Thanks for the info.

  7. Hi Tim! The primer I used was called HiTac by Bakor ( If you can't find that kind, I believe that Grace (Vycor) makes a primer as well. Just make sure it's compatible with ICFs, because if it's solvent based, it's liable to disolve the foam.

    You may not need primer if the weather isn't an issue. As long as your ICFs are clean (i.e. not dusty) and dry, the flashing should stick fine. You might want to try a piece of flashing first to see how it sticks.

    Yes, I will be flashing my doors the same way.

    For inside the windows, I'll have drywall up to the window frame on the sides and top. On the window ledge at the bottom, I'm going to put MDF with a countertop-like laminate on it. I'll run a bead of silicone on the inside of the window frame at the bottom and butt the MDF up against it. The laminate covered MDF is better for a window ledge than drywall because it's durable. Window ledges always get stuff put on them... coffee cups, plants, knick-knacks, etc. The laminate won't get scuffed up and spilled liquid won't affect it.

  8. Thanks, Marlon. Some followup questions:

    Did you consider something other than beveled cedar for the sill? I've been trying to avoid all wood on the exterior because of termites down here.

    Are all your exterior doors outswing doors? Or are you mounting any on the inside and then trimming out the exterior opening?

    Thanks. I've been encouraged by your site. Our ICF walls are finished as of today so we're moving on to the next stage.

  9. Hi Tim,

    Regarding the sill pan under the windows... I was actually trying to find a product call "Jam Sill" ( but I couldn't find a supplier here.

    Next I tried to find some sort of bevelled plastic or composite material. Again, nothing available around here.

    So, the bevelled cedar was sort of a last resort. Having said that, it's fine and will last a long time... although termites aren't a problem here.

    Maybe you'll have better luck finding some of the plastic products in your area.

    Let me know how you make out.

  10. Tim... sorry... forgot to answer your question about the doors. To be honest, I haven't decided what swing I'm going to have on the outside doors yet.

    What are you planning for doors?

  11. Marlon,
    I couldn't find a local supplier for jamsill either. Their web site says you can order direct - the price is higher than I expected to pay for a piece of vinyl.

    Regarding doors, we plan to use mostly exterior doors that swing out for all single doors except for one that my wife had already purchased. That one we'll mount on the inside and somehow (not sure yet) trim out the exterior jamb. We also have a double door (one fixed) that will swing in the middle so it can be mounted on the exterior. Mounting them on the outside seems to provide a better ability to weatherproof the door opening.

    The folks I talked to with ICF homes typically used outswinging doors because the thicker jamb doesn't let the door go beyond 90 degrees if it swings in. Outswing exterior doors are a little more expensive but not much.

    You can order special exterior doors that mount on the inside, but we're on a budget. We had a neighbor who had an inswing front door and he used hardie board to trim out the exterior jamb.