Subfloor finitum.

Exterior Shell, Sub-floor

After much ado, the subfloor and its many components are finally done. It’s one of those things where a lot of hours go in, with not a whole lot to show for it. The last step after insulating all the spaces between the steel joists of the trailer was to lay down 3/4 inch tongue and groove plywood to cover the entire surface.

The first sheet of plywood!

The first sheet of plywood!

We started on September 10th (Day 16 of the build since bringing the trailer out to our site) and finished on Saturday, September 12th. It was the icing on the cake so to say, but even with the reward of having that clean slate to start raising walls on, my energy was waning during this part.

It is very gratifying to complete each step, but it is a challenge constantly having to check your expectations at the door in terms of how long things take and how tricky they will be. Little failures or overlooked details are constantly acquainting you with the many shades of humility.

OOPS! Nothing a little PL Premium won't fix.

OOPS! Nothing a little PL Premium won’t fix.

Mental fatigue is definitely a bigger challenge than physical fatigue with all of this, which is something I never would have guessed. A steady effort of holding objects in your mind in 3D and moving them around in different positions to be correctly placed is exhausting!

First thing first, we laid down more sill gasket on all the steel that would be in contact with the subfloor plywood. This is to prevent thermal bridging – a fancy term describing how a more conductive material (steel) creates a pathway for heat to be quickly transferred through a thermal barrier (the insulated subfloor). It makes sense… the steel joists are going to get cold, and they IMG_20150910_155249run up through the insulation to touch our floor. A heat thief if I ever saw one. So the sill gasket provides an insulating break between the steel and our floor. It should help a good bit. We tried using PL premium as an adhesive to stick the strips of sill gasket down, but it didn’t work very well. A few pieces of tuck tape were much more effective.

The 3/4″ tongue and groove (T&G) plywood came in 4′ x 8′ sheets. Each sheet has tongue along one of the 8′ sides, and groove along the other IMG_94388′ side. The top and bottom (the 4′ sides) are square. Each sheet is also
stamped with a “This Side Down” marker, which results in each sheet lying concave up. In the instructional video that came with our plans, it
was explained that the sheets of plywood must run their length perpendicular to the underlying strength axes (which in this case are the steel joists of the trailer).  It is also very important to stagger the sheets so that the seams don’t line up with one another, creating sustained linear weaknesses along which the structure can bend. Alternating our seams at 4′ intervals gave us the maximum strength and unity our subfloor was capable of having.

So to be clear, it wasn’t just me who was tired, Tim was pretty tapped out as well. He was in go-mode though to just power through, and didn’t even stop to take many pictures. I tried to snap a few here and there to make sure the process wasn’t completely lost in time. The fact that each sheet had to be oriented specifically to face down the right way, and to have the tongue of one sheet tying into the groove of the next meant that we had to be really careful about each individual cut we made with the circular saw. Once that cut was made there was no going back, and, like the rigid board insulation, each sheet of plywood is worth a pretty penny!

We used 1.5″ screws to tie down the sheets of plywood. Every six inches along the perimeter (into the wooden side rails) and every twelve inches in the field of each sheet was our pattern. For the screws in the field, we were back to those #$^*)(@$% self-tapping screws again, since we were attaching to the top sides of the steel joists.

Fifth times a charm?

Fifth time’s a charm?

I really SERIOUSLY can’t stress this enough: invest in your fasteners. It sucks to pay a premium on the small stuff, but it will be so, SO worth it. The same goes for drill bits. If you buy (unknowingly or not) poor quality screws and/or drill bits, they will snap. Repeatedly. We used over 200 self-tapping metal screws and maybe 150 wood screws in total, and I didn’t count how many of those were duds. After this though we’ll be done with metal, and be able to work exclusively with wood (at least until the metal roof goes on, but that won’t be nearly as thick as the 1/4″ steel in the trailer joists).

Mind the gap! Lolz

Mind the gap! Lolz

As was the frustration with the 2′ x 4′ side rails, the plywood was pretty bowed, which made it difficult to fit the tongue and groove together completely, and to keep all four corners square. An important thing to remember with this is that wood swells, so you can’t abut adjacent pieces tight to one another – leaving about 1/8″ gap all the way around each sheet allows the plywood room to swell and shrink with varying moisture levels. Not doing this can result in your floor buckling under your feet, which is obviously undesirable. Our carpenter’s square is 1/8″ thick, so that made it quick to check our placement. The thing to keep in mind with these gaps is that they are constantly adding on to your total length, with each piece that is laid. This slipped our minds at first, and actually caused us a bit of hassle.

This sheet didn't line up properly. We had to take the screws out and skim a strip off the end of the sheet in order to make room for the next piece.

This sheet didn’t line up properly. We had to take the screws out and skim a strip off the end of the sheet with the skill saw in order to make room for the next piece.

The steel joists are on 2′ centres, so, the ends of two neighbouring pieces of plywood must meet each other equally at the centre of each joist in order to have enough room for the screws to bite into the metal on each side. These joists are the only surfaces on which the pieces of plywood could be attached in the field, so each one needed to be shared 50/50. Successive 1/8″ gaps add up fast, and without taking them into account, you can end up with one piece of plywood hogging a steel joist, with no room for the next sheet to tie in!

Other mentionable quirks include routing holes to accommodate the pieces of threaded rod, and cutting out pieces to IMG_20150910_221159allow for our wheel wells. It seems that with rough carpentry, it doesn’t matter how precise you try to be, it’s impossible to have everything just so. What a positively fantastic exercise for the nit picky hair-splitter in me!

As you can see in the header photograph for this post, on the right hand side of the trailer we ended up having to cut narrow strips to finish off the entire surface – much like with the aluminum flashing on the underside of the trailer. It would have been so much nicer to have the trailer a perfect 8′ wide by 24′ long, side rails included; then we could lay full sheets with no modifications required. But I digress… Again, since the tongue is only on one side of each sheet, we were left with a lot of wood that didn’t have a tongue for us to work with. Tim being Tim (economical and creative) decided to fashion a tongue himself on the long 10″ wide strips we had cut to fill out that right hand side. All it took was a table saw, a bit of cleverness and elbow grease.


A really great tip: take a speed square and pencil, and trace the edges of the steel joists onto the side rails prior to laying your plywood.IMG_20150910_174006 These lines can then be extended along the tops of your plywood so you can know exactly where the steel joists lie, and hence, where to sink your screws. It was a big help for us! We finished up the last few pieces and finally swept off our floor for the very first time. There were a few housekeeping tasks to clue up then, like trimming some of the perimeter overhanging edges of plywood, and using the grinder to cut off any of the snapped screw shanks left sticking up out of the floor. We also caulked around the threaded rod for good measure. All the cursing and frustration has been worth it, and we can now put in our order for 2′ x 4’s for our walls. Before you know it we’ll be raising the roof!



Tim taking it easy after a hard day's work.

Tim taking it easy after a hard day’s work.

Me, feeling proud :P

Me, feeling proud 😛




An Insulation Sandwich to Stand On.

Exterior Shell, Sub-floor

After we finished installing the flashing, we had to close up the seams between all the lengthwise sheets, as well as gaps around hangers and the tongue. To do this, we used a special kind of duct tape IMG_9245made by IPG that is typically used in duct work or on chimneys. It’s heat resistant, which I thought was an added bonus, and it came in a roll of about 45 m (omg, finally something in metric). It also came with a hefty price tag though- $15 per roll, so we bought just one to see how it went. Turned it to be perfect for our needs, and we were able to do the entire trailer with just the one roll! The ‘aggressive adhesive’ lived up to its hype and I feel very confident that we’ve been meticulous enough about moisture and tiny intruder prevention. As a side note, it’s miraculous how well the volume of our purchases have been working out. Little waste makes us happy campers.

There was something very oddly pleasing and enjoyable about peeling the backing off of each strip of this stuff and sticking it to our flashing. Smooth lines, and no more IMG_9266gaps! Simple joys 😀 There was a scattered spot (in the area where we first began our flashing, when we still sucked at it) where the flashing was bowed a bit extra – in those places we beefed up the closure using caulking; PL Premium, to be exact. This stuff worked really well, I’d recommend it. IMG_20150903_154529We also used this stuff all around the perimeter of the axle section, and the hangers belonging to the leaf springs and equalizers. If there’s anywhere on the trailer with a higher risk of water infiltration, we figure it will be around the wheels, so that’s why we did that.

Ready for insulation!

Ready for insulation!

Since the caulking takes a little time to dry, we had to space this out a bit, and did it over two days: September 3rd and 4th. We were going to head straight home for the weekend then to recharge our batteries, but we decided to spend the afternoon on Friday the 4th getting the subfloor insulation started. Now, since I did the post on insulation in the research phase, I’ve learned a good bit more about it all. You might recall that we had said we were planning on rigid board (also known as code board) throughout, but at that time I had no idea how expensive the stuff was. Turns out, a 2″ thick 4′ x 8′ sheet is around $50 a pop. So to cut down costs, we tried to come up with a compromise for our subfloor, since it is probably the lowest risk area for heat loss. A lot more research ensued, and to be honest, I wasn’t really able to get a straight answer on anything.

In the plans we bought, the instructions did not include the seam taping that we did on our flashing. They said to use one layer of 2″ thick rigid board, and another layer on top of the first, of 1.5″ thick rigid board with a radiant barrier (shiny silver backing) on the side facing upward. This would allow for the required air space between the radiant barrier and the plywood subfloor in order to properly reflect radiant heat back into the house. No vapour barrier was used in their method on either side. My issue with all of this was that not taping the seams left the underside of the trailer too vulnerable. Also, using a radiant barrier in the floor didn’t make a whole lot of sense since the majority of heat loss would be happening through the roof – I would consider it up there but not in the floor. And lastly of course, the cost of all the rigid was daunting. So we bought some Roxul mineral wool batts – really cool stuff! IMG_20150827_162456IMG_20150904_140455It’s made from volcanic rock (basalt) and steel slag, spun into a fibrous mass which is basically fireproof, highly moisture resistant, and much healthier and practical than fibreglass. It is recommended to install a vapour barrier with it though.

With all of this insulation research, my biggest concern was vapour barriers and if / when to use them. Theoretically, in a predominantly cold climate, you want to place a single vapour barrier on the warm side of your insulation (towards the inside) in order to block moist air moving from inside the house, into the wall / floor space and condensing on the insulation or exterior sheathing once it meets the cooler temperature towards the exterior. Since we had sealed the bottom, moisture and water vapour were effectively blocked from that side, so if any moisture got in, it would be kinda stuck with a vapour barrier on top as well. I was worried that putting that vapour barrier / retardant on the top would run the risk of turning our subfloor into a big ziplock bag of mould, if any vapour was able to sneak inside somehow. Oh the stresses… we decided against it in the end and went back to plan A to fill the entire trailer with rigid board. IMG_20150904_143856That way we don’t have to vapour barrier, and we’ll be adding extra structural integrity to our base. The rigid board is closed cell foam, and it is petroleum based of course, so it is intrinsically very adept at preventing moisture intrusion (and mould development). It’s printed on each board that at least 20% is recycled material, too. Our floor is going to be R-20!! Hooray for warm feet. The roxul won’t go to waste though because we are going to put it in all our walls 🙂

We have an account at the hardware store now, so we’re feeling very professional and important being able to say “Yes, put it on my account, please”! We bought our stack of insulation and the very nice people working in the yard offered to bring it over to our warehouse with their forklift! Gotta love rural Newfoundland. IMG_9276

Each (standard) bay in the trailer frame is 4″ thick, 23 3/4″ long, and 91″ wide. This meant we would get two pieces from each sheet of rigid board, and each bay would accommodate two pieces stacked on top of one another. There are a few exceptions to this, such as in the axle section, and the two end bays, so we adjusted measurements accordingly. We first started out cutting our pieces to size using our circular saw. This achieved very straight lines, and it was ok, but the IMG_20150904_163058blade spins so fast that it actually burns the foam a bit along the cut, and also, I find it a bit overkill / aggressive for this kind of material. The weight of the saw causes the sheet to bow in the centre along the axis where it is being cut, and this sometimes causes the blade to get pinched by the foam, resulting in the saw kicking from time to time. This is not fun. It is a pretty amazing machine though, I enjoyed using it when it was cutting smoothly, and it will be much better when using it on wood.

On day 2 of insulation, Tuesday September 9th, we incurred a power outage for the majority of the day, so we had to try a different method. As it turns out, using a utility knife blade to score the rigid board and snapping it along that cut works beautifully! I’d say even cleaner and faster than the circular saw, and safer as well. We kept this up even when the power came back on. Getting a really snug fit for these pieces of insulation is really important in order to block drafts and to have an efficient and economic subfloor. Why pay for heat if it’s going to escape out through gaps? I took a segmented video laying out the whole process of preparing a sheet of rigid board to place within the trailer frame- you can watch it below!

Using a regular handsaw works well too, and we used one for some of the smaller, thinner trimming we needed to do on certain pieces. And that bread knife… I gotta say, it was essential for those notches. If you’re a good hand at cutting homemade bread, you’ll be great at slicing insulation with the same knife. We finished insulating on September 9th, and bought our stack of 3/4″ 4′ x 8′ tongue and groove plywood for our subfloor as well. We’ll very soon have something to stand on!

Finished job!

Finished job!

The Aluminum Flashing Blues

Exterior Shell, Sub-floor

I’m writing this now after 4 of the toughest days on record of this entire project. I must say, I’m glad I waited until now, because this post would have been steeped in a lot more despair and frustration otherwise, haha. We started on Saturday, August 29th thinking we would do the entire job in one day. Hey, it’s just a bit of aluminum flashing! We said. Roll it out and just pin it on! We thought.

Tim, looking sad, brushing shards of metal out of his hair.

Tim, looking sad, brushing shards of metal out of his hair.

Not so much.

This is an excellent example of where theory and practice do NOT equal each other. However, there is a silver lining (other than the one going in underneath your trailer – hehe). With something extremely challenging such as this comes a great sense of accomplishment, and allows your confidence to grow, even if it’s just a little.

I’m not going to spend too much time on our failures and struggles, because neither of us really want to re-live them, but I’m also not going to sugarcoat this. About half way through this task, I asked a group of fellow tiny housers in desperation whether or not this was the hardest part of the whole build, and a lot of experienced people actually said it was. This gave me a little strength to keep on going, knowing that we weren’t the only ones who struggled, and that it was going to get better!

Flashing the underside of the trailer is an important step in any tiny house build. It ensures that any little critters looking for a home won’t end up sharing yours. Also, since we are insulating the bays in between our trailer joists, it will keep our insulation dry and in place. Lastly, it will deflect road wash and any debris or small rocks from the road when we’re towing our tiny house. We bought the majority of our flashing at Kent, and it came in 2′ wide, 50′ long rolls (we bought 2 rolls). A lot of people use galvanized steel flashing on their tiny house trailers because it’s cheaper, but all we could find was aluminum, so we went with it. Since our trailer cross members/joists are on 2′ centres (that means that from the centre of one joist to the centre of the next is 2 feet), we wouldn’t be able to align our strips of flashing width-wise because proper overlap (at least one inch) wasn’t attainable that way. The only option was to send the strips length-wise. THANKFULLY we had the good judgement from the beginning to not try and do full 28′ long strips… I think we’d have each other murdered by now if we had. We decided to break it up into sections, as per the picture.

Our trailer, broken into sections for flashing installation.

Our trailer, broken into sections for flashing installation.

We started in the red section, progressed to blue, then green, and finally purple. They each had their defining qualities, good and bad. Of course, as with anything you’re doing for the first time, the beginning is kinda ugly, and the end is kinda beautiful. I’m also really glad we chose (not on purpose though) to start at the back, where it is the most straight forward. The process basically dictated that we attach each strip, from left to right, overlapping each one by an inch. The perimeter is attached using wood screws (as it is attached to the wooden side rails), and the field is attached to the 1/4″ steel joists (C-Channel) with 3/4″ self tapping screws. We were able to cut our strips of flashing just using a utility knife against a straight edge. Going over the cut 3  to 4 times and then bending along that line would snap your piece off cleanly.

On deciding how to orient our overlapping edges, it was useful to think about how shingles work. The bottom pieces go on first, and you work your way to the peak of your roof, so that water will be directed down and away. BE the drop of water and imagine where you would go. We decided to have the flashing strips overlap such that at any lengthwise intersection, the left piece was on bottom and the right piece was on top. Since oncoming traffic would direct water towards our trailer from the left hand side (in North America, anyway), it made sense to us to overlap our flashing to protect infiltration from the left. Similarly, since driving would direct any water hitting our trailer from the front to the back, we overlapped the sections such that the front section (green) was underneath the middle section (blue), and the middle section was underneath the back section (red).

The good news is that aluminum flashing is light and flexible, making it easy to manoeuvre. The bad news is that aluminum flashing is light and flexible, making it difficult to get it flat and straight. SIGH. This was our biggest issue overall. I’d almost consider getting a slightly thicker gauge of flashing if I were to do it again, just so it would stay a little more rigid when installing. In the beginning, we were trying to hold IMG_20150829_144149up the strips of flashing using our hands and a few clamps along the edge. We also tried milk crates as stands, but they weren’t tall enough. These methods didn’t last, since only two of our clamps are really any good, and we just couldn’t get the sheets uniformly tight enough to the underside of the trailer this way. We did this for a whole day though, and then spent the better part of the next day re-doing it all. Every time we would drive a screw, the aluminum sheet would buckle slightly, in one direction or the other, creating dips and bows along the length and width of the piece we were working with. It was maddening. At last, we found the silver bullet, using long, narrow pieces of wood under the two adjacent sheets being worked with, along their centres, clamped at either end using a metal C-clamp OR a scissor jack.

Loosening your clamps a touch allows you to wiggle the sheets into place so that they’re square, flat, and properly overlapped. When they’re perfectly in place, tighten, and then you’re ready to roll around on the floor on a sheet of cardboard for a while. Drilling the pilot holes and driving screws into steel from UNDERNEATH the trailer was pretty miserable. To make it worse, every hole that was drilled spouted hot, sharp, metal filings that would rain down on your face, neck, arms, and into your shirt. Blissful. We’re going to be finding these little bits for days I think, in our clothes, in the bathroom, the kitchen.. everywhere. They grab onto your hair and your clothes, even after having been washed!

Up until now, I haven’t truly hesitated with anything connected to the building process of our tiny house; we’ve split everything 50/50. But once Tim was nearing the halfway mark, I will admit, I was questioning my capabilities and a little doubt snuck in. It was day three of this task, we had been working long days, often as late as 1:30am, and we had only just started to yield a little success with it all. I’m going to be honest, doing this kind of stuff tests you. It will test your relationship with your partner, your ability to stay positive, to be kind, to communicate effectively. Especially when one role of a task is significantly more demanding, both physically and mentally, than the other role. The person underneath the trailer driving screws can’t really see the steel joists that well, or the degree to which the flashing is buckling, so constant discussion and trouble shooting amongst each other is required. When my turn came, I was determined, but I did need a bit of a pep talk, and Tim did a great job 🙂 I’m psyched to say that I basically did the entire front end of the trailer: the green and purple sections.



The purple section probably took just as long as the green section, just because it was so time consuming to think through all the shapes and angle translations required to

Step 1 - Check it out and take your measurements

Step 1 – Check it out and take your measurements


Pieces that fit in around the tongue

fill in the spaces around the trailer tongue. It was also tricky accommodating the 4 hangers we installed on the corners for our scissor jacks, and the 6 hangers within the axle section. Measure twice, cut once, people!!

If you do cut a bit too much off, or you have any kind of gap, it isn’t the end of the world though. It can always be patched, or filled in with caulking, or even taped over with aluminum foil duct tape.

Step 2 - Trace out your cuts on to your sheet with a sharpie.

Step 2 – Trace out your cuts on to your sheet with a sharpie.

Also, a sharpie is perfect for drawing lines on aluminum.. just hard to keep the felt tip clean is all.

Step 3 - Make your cut!

Step 3 – Make your cut!

It kinda felt like a big arts and crafts project towards the end, and we really started gaining fluidity and momentum. By the end of it, we were feeling pretty good about it all, and it seems as though we have succeeded in protecting our investment from underneath. I might even go so far as to say I’d do it again… but maybe that’s the elation of being done talking. Here’s a few pictures we took on Day 4 of the finished product (Tuesday, September 1st).

Part of the green section

Part of the green section

Looking towards the back, from the tongue..

Looking towards the back, from the tongue..

Suggestions for anyone doing this themselves in the future:

  • Invest in an automotive ‘creeper’ (like a skateboard) so you can roll on wheels and not your back.
  • Make sure you have a combination square, a carpenter’s square, a utility knife, a measuring tape, large metal c-clamps and scissor jacks, a few 10′ – 12′ lengths of 2″ x 4″ or 2″ x 6″ wood (for bracing), and needle nose pliers. Of course the screws, drill bits, drill and driver go without saying.
  • If you have the means to flip your trailer over so that you can have gravity on your side when installing the flashing, DO IT!
  • Give yourself a break. This is hard work, and you will get through it in your own way, in your own time. Don’t rush it, because you will probably get even more frustrated and potentially end up wasting material.