Sub Floor: Wicked Choices

Preparing a sub floor (from an unrelated restoration)

Preparing a subfloor (photo from an unrelated restoration)

We have three weeks to get the sub floor in before the Spartan gets towed to Newhall to meet with the Nomads  on November 6th. (see Sam’s post 3)  So much to do!  Sam is scraping off all the old rust off the chassis.  Then he’ll use POR15, a product that forms a protective coating by bonding with rusty metal.  There is nothing green about this product.  The other option was to remove the trailer skin and transport it to Van Nuys for sand-blasting and powder coating.

Meanwhile, we have to search for suppliers for the sub floor lumber, floor insulation, belly pan and grey water tanks.

Lumber Many, if not most, vintage trailers have rotting floors from water damage due to leaks from windows, metal seams, ceiling vents and

Bathroom floor was rotted from leaks

plumbing. Then there’s the vapor that forms under the floor and walls.  After 60 years, the Spartan had all of the above.  The sub floor was rotted and had to go.  But replacing a trailer’s sub floor (all or part) can be a challenge.  Seems like there are as many ways to go about it as there are people willing to tackle the job.

Marine grade plywood is worth the extra expense.

Sam has already cleared out the trailer and has a clean slate.  He’ll use 3/4″ marine grade plywood.  We’d like to use sustainable lumber.  But that brings up all sorts of questions (It looks like this is going to require a steep learning curve.  See Treehugger links below.)                                                                  FSC lumber is available about an hour away.  But even that may not meet the standards of all environmentalists. It’s also a speciality item, stored in a separate lumber yard, required special delivery. For now we have to compromise.  We are looking plywood that is pretty green, not treated with formaldehyde and try to do better with the rest of the lumber.

Belly Pan We want a more sturdy belly pan that the conventional MDF or plywood variety that always seem to get damaged from scrapes or rot aways.  Aluminum will also keep out pests.   The thickness: 0.40 or 5053.  Another expense!

Flooring Sam is supposed to refer to the link below for sub-floor installation.

Fiberglass insulation was used under the floor of this restoration- may not the greenest choice but it is relatively cheap. .

There are other options. TRA Certification (Airstreams gets certified by them) suggested Eco Batt by Knauf which has some recycled content and it not supposed to off-gas.  Company site don’t seem to mention where the product is manufactured nor do they mention certifiable fair labor practices

Another solution is a 1.5″ layer of foam spray. A soy or castor oil based variety comes in a do-it-yourself kit. It has a high R value, seals everything in place and keeps bugs out.But it would require all the plumbing and electrical under the floor to be in place before the foam goes in.  How to do that before November 6th?  Sam is in class full-time and is rehearsing for two plays after-hours.

Another looks interesting:  Airstream is using a sheet of plastic on the belly pan then Refletix, which is also recommended by this Airstream forum.  Here is how one of the forum members used a similar product.

I have used Prodex, much the same as Reflectix throughout the whole 26′ restored Argosy. However, I have glued 1″x2″ urethane strips onto the sub floor underside. Cutting the Prodex by 3″ oversize I have overlapped it onto the frame members attaching it with 3M 5200 Fast Cure to the urethane strips and frame. Prodex has advertised “R” value of 14.7. Added air space between bubble foil and sub floor adds about two points in “R” value. I did the same thing in the walls using 1/2″x2″ urethane foam strips in order to create air space on booth sides. I have brought the Prodex along the ribs toward the inner skin trimming the excess 1/8″ high past the rib. This way the inner wall skins sealed the cut edges of Prodex. My 15000 BTU Carrier freezes me out at the lowest setting in 95+ degree direct sun. Thanks, “Boatdoc

Next up: the grey and black water tanks to go under the belly pan.

by the Spartan web lackey


Sustainable Lumber Standards:  Forest Stewardship Council (FSC) vs. Sustainable Forestry Initiative (Treehugger)

Credible Forest Certification

Airstream restoration, including the subfloor:

Partial subfloor replacement:       

This post is part of a series documenting Sam Breen’a Spartan Restoration Project. Please see his first post here and check out the archive here. The CSPA is helping Sam by serving in an advisory role, offering modest support and featuring Sam’s Progress by syndicating his feed from as part of our CSPA Supports Program.

Insulation and Chassis: Conversations With Timeless Travel and Aerogel


1946 Spartan, Timeless Travel

What kind of  insulation to use?  How to balance all the variables – sustainable, healthy materials that are also efficient.  No sense using green materials that aren’t going to be good insulators in a trailer warm or cool, as needed.

I talked with Brett Hall from Timeless Travel who has restored a number of vintage Spartan’s and many Airstreams:

Brett Hall:

Spartans are the best trailers. The body, which is made from airplane material, contributes about 70% of the trailer’s strength; the rest of the strength is in the chassis.  An Airstream is about 50-50%.  For other trailers, it’s all in the chassis [i.e. the body is basically useless.]

Timeless Travel uses PIC insulation

We use PIC insulation which is fiberglass without formaldehyde.  It has an R5 value, which is best you can do with a Spartan, which has an average depth of 2” on the wall.  Insects don’t like it and [I think he said it is fire resistant.]  Once installed, it has an R10-R13 value.  We use foil tape. The PIC has a lot higher R value than other stuff; we install it in panels.  PIC insulation is fairly green, doesn’t outgas.  When installed, it creates a vapor barrier.

There is a lot of exhaust inside the trailer, from cooking, heating, showers, even humans [people give off 2 liters of water/day.] That goes to the outside of the skin.  The air gap helps air from getting in and also air going out.

Steven Harasim, chemical engineer with Aerogel

Q:  We have a limited budget, but we are interested in following up with your idea of using strips of Aerogel (Thermogel) over the ribs along with some other form of insulation.  What is the R-value of Aerogel?

Our product has an R4 value for each layer (the idea is to layer it). Harasim’s idea was to use some other kind of insulation in the gaps and then use strips of aerogel over the metal ribs before putting the paneling on (see the above photo where exposed metal ribs aren’t covered by insulation.)

Harasim says this method would get rid of the thermal bridge where the steel is in direct connection with the paneling which is very inefficient, thermally.

He said steel has a conductivity far greater than wood. When the metal is  exposed and it touches the walls it acts as a much larger sink in terms of conductivity  than even the gap in between where the insulation would normally go.  So the idea is to isolate that contact by putting a strip of Aerogel on the metal beams.

Santa Clara University’s submission for the 2009 Solar Decathlon

Harasim mentioned the Solar Decathlon (, a competition sponsored by the Department of Energy  where college students design homes that are almost entirely net zero homes.  According to Harasim, Areogel was used in 4 out of 10 of the winning designs, including the Refract House (photo above) a collaborative effort between the University of Santa Clara and California College of the Arts (click to download PDF of project manual,  lower right column)

Coincidentally, Harasim actually used to work for the PIC insulation company that makes the stuff that Timeless Travels uses.  He says it is an “adequate solution”.  From looking at the  pictures I showed him he said, he says “It is well insulated.  The only downside is that the still the steel studs are still exposed.”

He continued:  “What is difficult about the Spartan is the varying cavity size.  But I don’t see anything wrong with this solution. The PIC foam would be a mid point solution.  The aluminum foil is 100 percent recyclable.  The foam is not but it has a higher R-value than other foams per mass basis.  It is more efficient than other insulation.

Question:  Is the PIC insulation “green”?

Harasim:  It’s hard to describe insulation as being “un-green” since its primary objective is to save energy [I suppose some people could argue with that statement]

Q:  Does you think it would be more green to use something like a newspaper product?

The newspaper, being 100 percent recycled would be an advantage, but overall probably not because of the insulation value and the difficulty of installing it in a trailer.

Q:  Do you think Areogel might be willing to donate some materials or otherwise help with the cost?

We aren’t against it but they are stretched pretty thin right now. We are a new company and have already been donating (I bet to the Dethlon).  But he would help with advise on the installation.  And the strips actually come from a different company, Thermal Block, and they may be able to work with you as well.  He’ll give me all the info.

Note: Timeless Travel uses a different kind of insulation in the floor. (I don’t remember why).  He may have said the stuff is styrene or else fiberglass??


New chaissis, Timeless Travel

Timeless Travel’s Brett Hall said Spartan trailer chassis often have structural problems, especially from the wheels back.  “We start looking right away for problems.”  About 40% of the Spartans have serious problems, about 10% need work.  (It should be noted, however, that Timeless Travel tends to add 2,000 – 3,000 additional pounds on average to their renovated (high end) restorations.

Note:  Hall said the original Spartan chasis were built by a third party.


Hall added that it’s very important to pay attention to wiring.  The trailer must conform to the National fire Protection Association’s Standards for Recreational Vehicles (NFPA 1192)






click here for PDF:

Hall rattled off all kinds of things that I couldn’t catch (I was taking notes from the floor of the grocery store).

The gas pipe has to be grounded to the chasis, for instance.

The main thing is that you have to be very careful.  He said electricians think they know what to do and they don’t read the code.  He said READ THE CODE!!


He started to tell me about the belly pan but I have to call him back…

This post is part of a series documenting Sam Breen’a Spartan Restoration Project. Please see his first post here and check out the archive here. The CSPA is helping Sam by serving in an advisory role, offering modest support and featuring Sam’s Progress by syndicating his feed from as part of our CSPA Supports Program.