Tiny House October: Subfloor Part 1

October is a big month for the project because we are officially starting  the Build! Starting from the bottom up, of course, which is the coolest thing about building a house, subfloor was the order of business. As of right now, the plan is to have a roof by mid-November (and before the snow flies!).

Before that, a quick note about the layout. In an effort to get a more realistic feel for the space, we bought a bucket of chalk and measured it out on our driveway. Once we were able to actually stand in our drawing, we saw a lot of changes we could make to use the (small) space to its fullest potential, and we ended up changing about three quarters of the main floor layout. (Those blue outlines are the actual sizes of our toilet, sink and shower, oh my!)

Back to the subfloor…Since our trailer was made to order, we didn’t have to mess around building a floor frame or tacking the aluminum belly pan on, but we did have to caulk the belly pan to keep water and critters out. Mr. W guessed we would use 15 280ml bottles of caulking and we came in at 12. We washed the trailer with soapy water first and made sure it was good and dry before we started and then we filled every crack, gap and seal we could see.

Once the caulking was dry, it was time to lay in the insulation. Let me say, this was more exciting than it might sound. To have looked at the empty trailer for weeks without being able to work on it and then to finally be able to fill it up with insulation…finally felt like we were starting to build something. As I discussed in a previous post, we used Roxul insulation, which meant the only equipment we needed was a tape measure, a bread knife, and some gloves. However, while drawing up the plans for the house frame, Mr. W. found that we would need to grind some of the bolts off that had been welded to the frame, so insulation went in once the trailer was 10 bolts lighter. (We touched up the places where the bolts used to be with some Tremclad to keep it from rusting).

IMG_6893 IMG_6896 IMG_6898

IMG_6923 IMG_6918

For the record, this Roxul wasn’t nearly as itchy as fibreglass insulation. We rinsed our arms and our faces afterwards and that was it.


Once the insulation was in, we put closed cell weather stripping along each surface of the frame to stop any heat from the inside of the house from traveling out where the plywood meets the steel frame .


Next step, vapour barrier. We used regular 6mil plastic and that awful black, non-drying vapour barrier sealant. Whether to use vapour barrier in the subfloor or not was a bit of a tricky decision, since there is no real straight answer in the tiny house research available online. A lot of builds we’ve seen, including professional ones from Tumbleweed, don’t use vapour barrier. But we also didn’t see a ton of builds in a climate like ours, where we get everything from hot and humid to cold and wet (a lot of tiny housers that you find online are building in warmer and/or less dynamic climates). After researching forums for building houses with crawlspaces in an Ontario climate, we decided we would go with it.


Voila! An insulated, weather stripped and vapour proof subfloor! I’ll be back in a week, when the plywood is laid!


6 thoughts on “Tiny House October: Subfloor Part 1

  1. Very Cool !!! glad to see it coming together !! (I hope you two work together better than Greg and I……..when 1 zags the other zigs…….not good) Keep up the great work !!


  2. Very professional! Did I send you the video of the person who used the kitchen cabinets as the steps to the loft? Now that was a real space saver.
    Looking forward to your next installment!


    1. Thanks :) I don’t know if I received that video from you, but I have certainly seen a lot of great ideas for storage stairs. We’ve designed a set ourselves! Now we just have to see if we can build them lol


  3. Hey there! We are also building a tiny house in Canada where the weather is not so nice as our southern neighbours. I’m a little nervous about our subfloor.. we’re dropping insulation in tomorrow or the next day and I’ve been torn about whether or not to do the vapour barrier – don’t wait to create a big zip lock bag of mold, but don’t want to lower our R-value by letting interior vapour get into the subfloor! Ahh! How has it worked out for you guys? Any issues thus far?


    1. Hi JessandTim! So sorry for such a late reply! I think Matt and I both thought the other had taken care of it! As for how the vapour barrier has worked out…we can’t really say since we’re still in the building process. But I will say this – this week we took the tarp off to find that the house was SOAKED with rain. Our tarp had never failed us before and we had no reason to think it would. Out subfloor was fairly saturated in some places and if we didn’t have a VB under there our insulation would have been wet too.

      We made our decision based on the idea of building a house with a crawl space as opposed to a poured basement, the former of which do have a VB and the latter of which does not. We felt that the tiny house was kind of close to a house with a crawl space and went from there. Not to mention, the house we a currently renting has a crawl space with no vapour barrier (it’s a really old house) and we get terrible drafts up between our floor boards in the winter! Obviously this is also an insulation issue but in order to re-insulate it out landlord said he has to get under there with a VB first.

      So based on all of this I still think we made a good decision. What did you end up deciding?? We’d love to see pictures of your trailer so far!



Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s