How-To install a Window in Your Tiny House

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. I dare the rain to try and penetrate!


Bigger does not always mean better. Progress does not always mean forgetting our roots in order to forge a new future. Blogger, photojournalist, and hobby farmer Andrew Odom has spent much of the last few years rediscovering the lost art of living, growing, and being truly happy. Visit him online, find him on Facebook, or follow him on Twitter.

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    Kent Griswold - October 20, 2011 Reply

    Thanks et, I’ve fixed that link.

Wolf Lahti - October 20, 2011 Reply

Those instructions regarding the membrane were not only unclear but self-contradictory. Perhaps an illustration or two would help?

Josh - October 20, 2011 Reply

The wonderful thing about building your own tiny house is that by-in-large the basic construct is the same as any other building.

I think you mean “by and large.” Like so many other terms we use today, this one originated with sailors. I believe it’s a combination of the terms “by the wind,” which means sailing into the wind, and “full and large,” which means sailing with the wind from the stern, keeping the large mainsails full. A ship that handled well “by and large” sailed in either condition well, and so the phrase came to be synonymous with “in any case.”

I knew reading all of those sailing books would come in handy someday.

    anotherkindofdrew - October 20, 2011 Reply

    Well don’t I feel silly now. Actually, I feel enlightened. Thank you for correcting me and teaching us all a little something Josh.

      Josh - October 20, 2011 Reply

      I should be a professor of mostly useless knowledge.

anotherkindofdrew - October 20, 2011 Reply

@Wolf – You are right. The membrane explanation is a bit sketchy. I am working on my technical writing proficiency. As I am sure you know sometimes what you think is clear is so only because you have it in your head (or have done it yourself) as well. I am going to work this weekend (when I have some time) on a sketch that will illustrate my technique better. Thank you for the polite correction.

Benjamin - October 21, 2011 Reply

Call me confused.

I’ll wait for the illustrations. Or better yet would be a video.

    anotherkindofdrew - October 21, 2011 Reply

    The illustrations may come quite soon. However, I have no windows to truly install so a video may not be possible at this time. I am not a contractor or professional builder, per se, so I am not installing windows on a regular basis. My apologies Benjamin.

ian - October 22, 2011 Reply

Just wanted to say this is the same method I use and the best I have found but you definitely need some video or images for someone just learning.

I learned this method from a video on youtube, but sure of the link but I am sure it would come up under ‘how to intall windows’ or similar.

Brian - October 25, 2011 Reply

Much advice will be given on this article about the proper way to flash a window. Drew’s description is technically correct, though the illustration or video would help. Try

Also, never, ever, ever caulk the bottom fin of the window to the outside of your flashing. Water WILL get into your window assembly and you WILL want it to drain. Instead, caulk the gap from the inside.

My twopence

Surly Liettle Cerley - October 25, 2011 Reply

Thank you for providing this instruction. Any more instructions for those of us who cannot afford to pay someone else to build for us but have no experience are certainly appreciated!

HE Windows - December 18, 2018 Reply


Glad you mentioned not caulking the bottom fin of the window to the outside of the flashing. Water always likes to find the lowest point so this is crucial. We are actually thinking of building a portable sauna shortly and the information here will definitely be beneficial to use. We are used to installing windows in the Albany, NY area so knowing that it is much the same installation process is very helpful.

Thank you!

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