The wonderful thing about building your own tiny house is that by-in-large the basic construct is the same as any other building. There are a series of tried and true steps that hold fast for your tiny house trailer, your small home, and the McMansion down the road. You want to decide on your foundation, set the subfloor, frame out the house, add windows and doors, put on your sheathing, etc. Now notice I said add windows and doors.
Windows are one of the most predominant features of a tiny house. Buy using them strategically you can help heat and cool your home (think passive solar and cooling), make the space appear larger, and properly ventilate for appliances and heating units. But how do you do this? Do you put up sheathing first and then cut out for windows? Or do you hang the windows and frame around it? The following is my method and what I have found to be most successful.
1. Rough it up. In order to rough in your window you first need to measure the width of the rough opening at the top, middle, and bottom and the height (at both sides and in the middle). If you come up with a difference in the three width measurements you may need to fill the opening with some stud material to level or plumb the opening. You also want to make sure you follow the directions on the new construction window which will more than likely call for the dimensions of the window to be 3/4″ narrower and 1/2″ shorter than the smallest width and height measurement.
2. Insane in the membrane. Rain is NOT our friend when it comes to installing a window (or even a door). That area where the window meets the wall can be a nightmare waiting to happen. To combat any leaks you should cut a 6-inch-wide strip of self-adhering waterproof membrane about 20 inches longer than the window’s width. Center the membrane under the rough opening and adhere it to the existing house wrap. Make sure its top edge doesn’t go past the edge of the rough opening. Then cut two more strips of membrane a foot longer than the height of the opening. Center and attach. Make sure to overlap the strip under the window. Now deal with the width by cutting a strip of membrane about a foot longer than the window is wide. Center and attach it so it overlaps the two side strips. By now you should have four strips of membrane around your window with the top and bottom strips overlapping your side strips.
3. Install. This is perhaps the most gratifying step as it is the one you see the most immediate result. Pick up your window and insert it bottom first into your rough opening. You want to first fold out the window unit’s nailing fins for proper tacking. When you see the gaps between the sides of the window and the jack studs equal on both sides tack the nailing fin to the sheathing at one upper corner with a common roofing nail being sure not to drive it all the way in.
4. On the level. Once you have tacked your window into the rough opening use a 4′ level to note the window’s high side. Then hold the level against the jamb on “the high side” and nudge the window until it appears plumb at that jamb. Tack the fin at the lower corner on the same side of the first nail.
5. Drive it home. Measure your frame diagonally from corner to corner to check for square. You should find that the window is within 1/16″. If not, you may have to adjust the frame. When the sill is level and the frame square, drive it home by nailing the sides, top, and bottom of the nailing fin. I find that driving one nail through every other pre-punched hole is plenty.
6. Is this record skipping? Repeat step 2 on the outside of the window.
At this point you may or may not have to deal with flashing or other sealing strips provided by the manufacturer. If this is the case, directions should be included with the window. The advanced installer may even have to use a siding break to bend a piece of flashing for superior protection against leaks.
FOOTNOTES: You simply can’t depend on just the trim and the housewrap to stop water from leaking in. Take the extra time (and money even…..remember, it is your HOUSE after all) to seal the perimeter of the opening with sticky sheets of self-adhering waterproof membrane, strips of metal flashing, and liberal amounts of window & door caulk. Any rain that gets by one of these layers will be stopped by another.