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.

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