Floor insulation methods

[ssutton]

Planning the build and wanting to know about insulating the floor. I will have a welded steel tubular frame (2"X3") and plan to install Advantech flooring that has been fiber glassed/resin coated to water seal. Beyond that, I have not planned how to insulate the flooring. A design goal is to be able to camp in cold/hot weather so camper will have AC and heat.

First thought is to install foam panels under camper....but I am afraid that this will hold/trap water and moisture against the frame and under body accelerating rust and rot. Second thought is to install sheet foam insulation on top of the advantech and then install a thin sheet of luan or other type of floor covering on that. My concern with this approach is that the foam will eventually compress and cause low spots in the floor and loss of insulation properties.

What solutions have others used for this?

Thanks in advance,

Scott

[RandyG]

Many sandwich foam in between sheets while others just think their mattress is enough insulation.

[MtnDon]

The pink and blue variety of foam has a compressive ratings of 15 PSI in the normal material; there are versions with 25 PSI rating as well. Polyisocyanurate (foil faced on 2 sides) has a rating of 20 PSI. The foam will not compress any measurable amount if topped with a plywood layer. Using the usual 5 mm lauan would probably be okay for most loads except point loads like stiletto heels or impacts from dropping something heavy on a corner / point.

[les45]

I insulated with 1 1/2" of foam board over a 5/8" plywood deck then a sheet of luan over the foam. It makes a very sturdy surface as I crawled around on it for a long while doing the interior trim and electrical with no dents or damage to the luan. If you install a full length mattress over it, then there is very little pressure on the luan.

[George Taylor]

I did what the last post says. I put 1/2 ply first, then the foam, and a sheet of luan. I know our tear is well insulated. Stays cool in the summer with the fan on, and can stay warm in the fall.

[bobhenry]

I too have placed closed cell foam between the floor sheathing and a light top final floor of 3/8 osb. It's stays warm in cold weather and helps to insulate in hot weather. The foam is protected and will not trap water and the under side of the bottom floor sheet is well coated with a protective coating.

[Rainier70]

I insulated the floor of my cargo trailer by putting 2 inch pink foam between the rails. It made a huge difference in the temps in my trailer. Cooler in the hot season and warmer when it is cold. Quieter too! I have only traveled a couple of hundred miles with it so far, and about 30 or so miles was gravel roads. It is showing no signs of wear. I live where it is very dry though so I am not as worried about moisture as others may have to be. Some pictures of what I did are at the bottom of this page:
viewtopic.php?f=42&t=55219&start=60

[alaska teardrop]

Planning the build and wanting to know about insulating the floor. I will have a welded steel tubular frame (2"X3") and plan to install Advantech flooring that has been fiber glassed/resin coated to water seal. Beyond that, I have not planned how to insulate the flooring. A design goal is to be able to camp in cold/hot weather so camper will have AC and heat.

First thought is to install foam panels under camper....but I am afraid that this will hold/trap water and moisture against the frame and under body accelerating rust and rot. Second thought is to install sheet foam insulation on top of the advantech and then install a thin sheet of luan or other type of floor covering on that. My concern with this approach is that the foam will eventually compress and cause low spots in the floor and loss of insulation properties.

What solutions have others used for this?
Thanks in advance,

Scott

Scott, a sketch & a few details of your design would help in other members replying with suggestions.

Assuming that you're building a stand-up trailer using aluminum structure on a steel chassis, I'll offer a different solution to the usual wood floor.

Consider an .063" aluminum sheet attached to the top of the steel chassis with just VHB tape or VHB tape & rivets. 1", 1-1/2" or 2'' EXTRUDED polystyrene insulation laid on top & sealed with vapor barrier tape at the edges. Extruded polystyrene (pink/blue) is commonly used as a floor underlayment, even for cement floors, and will not crush or absorb moisture with a proper floor covering for the intended use.

For a stand-up trailer, I'd suggest manufactured fit together flooring laid on top of the foam board for durability.

As I see it, the advantages to this method are no glue or black goop, no materials that attract & absorb exterior or interior moisture, a solid protective underbelly & a solid warm floor.

After all, your question is about insulation. On any off-the-ground structure the underside surface will be the same as the ambient temperature, therefore, the quality & R-value of the insulation will make the difference in how warm your feet are, or in the case of a mattress on the floor teardrop how warm your butt is.

Also, the interior moisture attracted to a cold floor can create damage & mold on the floor & up the walls. Especially in the case of a mattress on the floor that absorbs interior moisture in & around it. And the method provides for full coverage insulation without any thermal bridges between the chassis steel or extra wooden floor framing. The method might also save you some weight over a wood floor.

Ideas:

Manufactured flooring

Vinyl flooring

1/4" oak ply flooring

Fred

[Nobody]

There probably as many answers to your question as there are builders on this forum. None are 'wrong' or incorrect. What's right for one person may not work as well for another.

I built my TD in 2006, using an HF 1800# trailer & a couple of profile drawings I expanded from quarter inch graph paper. I built my floor from ripped spruce 2x4's, 1x6 pine for side rails, & 1/2" CDX ply for the decking. After the 'floor' was completed I inverted it on a couple of sawhorses & 'painted' it with asphalt roofing compound. Contrary to conventional wisdom, the coating wasn't nearly as 'stinky' as expected, & the 'tackiness' only lasted as long as it took to dry (overnight). I then cut pieces of 1" styrofoam (Dow 'blueboard') to fit the recesses under the floor, installed them with PL Adhesive, & as an extra caution, I used small pieces of scrap wood as 'battens', 'nailed' to the floor frame with 18ga brads from my HF nailer/stapler. Almost 8yrs & 20K plus miles later (towed thru all kinds of terrain from freeway to National Forest/BLM back country roads/trails) the foam shows considerable stains/marks of travel, a few tiny 'gouges' probably from road debris, but NO deterioration or tendency to 'de-laminate' from the floor. In SE New Mexico in 2010 we encountered standing water in the streets of several towns, that in places almost 'floated' the TD. I've also driven through lots of heavy rain/T'Storms where I'm sure the tires & passing vehicles sprayed lots of water up under the TD. I've found no indication of residual moisture nor any evidence of rot in the wood portion of the floor, nor corrosion to the metal of the trailer chassis. As an aside, I live in central Arkansas where our average humidity is quite high & equipment not properly protected has ample opportunity to suffer ill effects from it...

Here's a few pix of my floor under construction





This how the underside looks this morning (not bad considering what it's been exposed to since 9/2006)