Stick to the Plans!

Friday, January 17, 2013, 6:35 AM at home in Santa Clara

Despite being a little bit tired from waking up early this morning, I am excited about my day.  It’s another day of working on the tiny house.  I have a plan for what I’m going to do today and I think I know how to do it.  I spent a couple of hours last night installing rubber flashing on the bottom of my pressure treated floor frame (see more on this below).  I also added a few two by four nailers in the right position for the plywood floor that I hope to install this weekend.  I think that’s going to form a good barrier between the treated wood and my aluminum flashing.  After several nights this week of trying to figure out how I was going to attach flashing to treated wood, stressing out about it, researching it, not sleeping over it and shopping for the extra supplies I needed, it was really nice to actually do some work.  I decided that my ratio of hammering nails to solving problems needs to be a lot higher because when I actually get to hammer some nails, it makes me feel really good.  I enjoyed the work I did last night and I’m looking forward to more of it today.

Rubber Flashing on the Treated Wood

Rubber Flashing on the Treated Wood

Today’s Epiphanies:

The big thing I learned this week is … don’t deviate from the plans!  The plans only called for pressure treated wood around the perimeter of the floor frame, not in the middle.  Last Friday, I made a last minute decision to use pressure treated wood throughout the floor.  I made this decision based on the casual recommendation of a neighbor whom I barely knew, who just happened to be walking by when I started to build my floor, a person who knew nothing about my plans.  Instead of trusting the people at Tumbleweed who have spent countless hours figuring out the best way to build these tiny houses, I trusted a random person walking down the street.  In the end, this decision created hours of extra work, added expense and a serious amount of frustration to my week all for a final product that I’m not sure is better than the original design and could possibly be worse.

I am extremely grateful to Andrew for discovering the biggest problem with our pressure treated wood decision.  It turns out that you cannot attach aluminum flashing to pressure treated wood.  You also can’t attach the aluminum flashing with regular staples.  The chemicals in the pressure treated wood will corrode and destroy the aluminum and any steel that is not galvanized or stainless.  If I had followed the plans, I would have used regular wood in the interior of the frame which would have allowed me to use the aluminum flashing called for in the plans and regular staples.  Now that I have used pressure treated wood, I need a different solution.

The second problem with our pressure treated wood decision was pointed out to me by Meg Stephens from tumbleweed, who called me this week in response to my requests for help.  She pointed out that pressure treated wood is much heavier than dried lumber. My decision would not only result in problems installing the flashing, but would also result in a heavier house. When you’re building a house on a trailer, weight matters.

Like I said, the people at Tumbleweed have thought about this for a long time.  The things they have put into the plans are there for a reason.  Given my low level of construction expertise and knowledge, deviating from the plans is more likely than not to add to the difficulty, time and expense of the project while subtracting from the quality.

Final solution for dealing with the pressure treated wood:

  • Use the aluminum flashing that I already purchased even though it will rapidly corrode if placed in contact with treated wood.  Another option would have been to use galvanized flashing.  However, galvanized flashing is at least four times as heavy as aluminum flashing for the same square footage (again adding to the weight of the house).
  • Install one layer of stick-on rubber flashing on all downward facing sections of treated two by fours in the floor frame to separate the aluminum from the treated wood
  • Staple the aluminum flashing to the floor using stainless steel staples which will not corrode in the treated wood

Final cost of deviating from the plans:

  • $50.00 for pressure treated wood
  • $50.00 for rubber flashing
  • $12.00 for stainless steel staples
  • 6 hours of research required to determine this solution
  • 1 hour of shopping for new materials
  • 1-2 nights of poor sleep
  • 2 hours of installing rubber flashing on the bottom of the floor
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2 Responses to Stick to the Plans!

  1. Jay says:

    Galvanic corrosion is a tricky one. However, I’m surprised there wasn’t a reaction between the stainless steel and the aluminum? How did the flashing hold up. & could you have simply used tyvek as a barrier between the aluminum and pressure treatment… Wait, that still lets moisture through… Perhaps 6mil plastic or a sheet of thin gauge Epdm rubber roofing(that butyl based tape is kinda similar). Yet, I got a whole 24’x9′ of Epdm for $340. I’m sure perhaps strips and glue might have saved money. I just can’t believe how much that flashing tape costs up here in the northeast.

    Anyways, please let me know how the stainless staples and aluminum flashing worked out after two years?

    • Hi Jay. So far the staples and aluminum flashing seemed to be holding up well. In the long run, even if the staples completely corrode and disappear, the aluminum flashing is not going anywhere now because it is sandwiched between the subfloor and the trailer frame and I also have lag bolts going through the frame and the flashing into the subfloor. The staples really just hold it in place long enough to flip it over and attach it to the trailer.

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