Post construction insulation install?

[Robbie]

Hi guys (and gals),

My benroy is almost ready to be mounted to the frame and I'm having some change of plans going on in my head right now. My floor construction is Pine 2x2 framing with 1/2" OSB flooring. When I started my build I didn't think I was going to get as into it as I've now become so I ditched putting the insulation in the flooring.

Now as I progress further and my wife gets more involved we have grown to love this little thing and are planning on keeping it for a while. I am wishing that I had put the insulation in the floor at the beginning. So my question is, how can I get insulation into the flooring with the main box already being built?

If you want some pics of my build my journal is here:
http://tnttt.com/viewtopic.php?t=45640

I was thinking of just tipping the box over on its side and putting in the 1.5" thick blue ploystyrene foam board in all the voids and then covering it with 1/4" plywood? Or even just some rubber sheeting glued and sealed real well to keep water out?

I've seen the blue foam board installed with only screws and fender washers into the floor but with there only being 1/2" OSB on mine I don't think there is enough material to get a successful bite, and I don't really want to screw in through the floor.

Any other ideas?

Thanks!
Robbie

[absolutsnwbrdr]

I was thinking of just tipping the box over on its side and putting in the 1.5" thick blue ploystyrene foam board in all the voids and then covering it with 1/4" plywood

I'm in the same boat as you Robbie. Didn't insulate the floor on my last one - just laid a 3/4" sheet of insulation on the floor inside. On my current build, I didn't really plan on insulating the floor, but now I'm thinking that I might as well just do it.

Since my floor is already on my frame, my plan is to cut some foamboard panels to fit underneath in the framing, then paint one side of the foam before installing them. Then stick them in place with construction adhesive. After the construction adhesive is dry, just caulk around the perimeter of each square. The foam is light enough that it really shouldn't need any mechanical fasteners. Just don't skimp on the adhesives and it should be fine.

There are adhesives specifically for polystyrene insulation....
http://solutions.3m.com/wps/portal/3M/e ... nsulation/

[Robbie]

That's exactly what I need! I think I'm going to use the 1" thick foam board instead of the 1.5" so I can add a little trim piece to the floor framing to help hold that foam in there for a little added security. Then I too will caulk around the edges and seal/paint the trim pieces.

Thanks for the link to that adhesive Zach!

[DMcCam]

Hi Guys, just a note about insulating the deck. Most of the earlier plans and builds used just 3/4" plywood. Many owners I've talked to who own them have camped in below freezing whether warm and toasty. The thing to remember is that you'll have 4" -6" of mattress under you; that's a lot of insulation. Our pals Debbie and Randy have a stunning woody teardrop that has this construction but I think they used 1" decking. That's what I did too. I wanted all the headroom I could squeeze out of the 4' height. Just something to ponder gents.

All the best,

Dave

[Robbie]

Ya I thought of that too. I'm sure I'd be fine without it but I figure its cheap and relatively easy to install and will provide a little more reassurance. The thing I am most worried about is condensation building up between the mattress and the vinyl flooring. I was hoping some insulation under the floor decking will deter that from happening.

[Oldragbaggers]

I have seen a lot people mention that they think the mattress is adequate insulation and I'm sure that's true, but I think if they check the underside of their mattress in the morning they may occasionally find it wet on the bottom.

[absolutsnwbrdr]

but I think if they check the underside of their mattress in the morning they may occasionally find it wet on the bottom.

There were a couple occasions that I did find some moisture underneath the mattress. It was only in the VERY cold temps, but it did happen. Fortunately I had purchased a waterproof mattress cover from TJ Max for about $10.

[aggie79]

Robbie,

I would just add a layer of insulation on top of your deck. If you are concerned with puncturing or denting the insulation you could add a layer of 1/8" plywood or masonite. I don't think there is a need to do any framing other than maybe a perimeter nailer strip if you add the plywood.

Take care,
Tom

[bobhenry]

All 3 of my trailers are done just that way !

With Chubby It was no problem to give up 2" of height as he is tall enough I was able to do the electrical wiring setting in a camp chair. I simply cut 2 layers of 3/4 blue foam layed it on the floor inside and added a top layer of 7/16 osb to protect the foam.

The barn was even taller and I did exactly the same method.

Now my little 4x7 put me in the little teardrop relm and it was a bit more difficult to give up the height but I did, and in about 6 weeks when I am out camping in January in Indiana I will be glad to have the layer of insulation not only in the floor but 1" in the sidewalls and 1 1/2 in the roof.

It is not just for heat either, cooling with AC in the summer is far more effecient as well.

[Robbie]

I thought of adding a layer right on top of the floor but I already have my door jambs installed which sit about 1" above the floor. So it would be a tight fit to get those in there with the door jambs unless I sectioned it, which I really wouldn't want to do. I think I am just going to do like Zach mentioned above and add the foam to the voids underneath with a good adhesive and then add a little .5" x .5" nailer strip underneath the foam and nailed into the floor framing to help hold the foam up there. Then just seal and paint over everything with black paint.

[jstrubberg]

Installing the insulation on top could also leave you with wet OSB, not a good thing.

I would flip the unit on it's side, insulate between your "joists" with 1 or 1.5 inch OSB, then cover it over with either ply or prefereably rubber, like you said. That way if you get any condensation from the temp changes it's between the foam and the coated side of your OSB.

[Miriam C.]

You can use some wide washers and screws to help keep the insulation up where it belongs. Seal it so the air doesn't get under and send it flying. As for wet OSB....you can dry it out when you get home. Better than a wet mattress...Really I would just add to the inside.

[mezmo]

Hi Robbie,

Someone on the forum [sorry I can't recall who] got some of those @ 2ft
square multi-colored denser foam pads, @ 3/4-1in thick, that fit together
with either jig-saw piece like edges or box-joint like edges. They're used
for kids play areas or used like anti-fatigue mats. Easy to trim to fit and
they stay in place with out gluing and such. You could trim them to fit
around the door trim. If you wanted thicker insulation just double them
up or us a 3/4-1in sheet of the foam insulation underneath the squares.
That might be a cheaper and less work intensive solution? Since it's under
the mattress the colors don't really matter. I've seen them at Sam's Club
and the big box home improvement stores.

Cheers,
Norm/mezmo

[Shadow Catcher]

The insulation in our floor is the 5" foam mattress. Don't see the point of anything else unless you are camping in sub zero temps.

[48Rob]

If you choose to add insulation under the floor, there are two concerns to keep in mind.
The first is damage from road debris.
It is somewhat minor, as you can easily repair small dings with caulking.

The second though, is much more critical.
If you don't have a positive 100% seal, water can and will get between the foam and the bottom of the floor.
If it gets in, chances are it won't easily drain back out the same hole(s).
Unfortunately, you probably won't know you have damage until it becomes so bad that repairing it will be a major undertaking.
Having applied tar or whatever waterproofing to the underside first will help, but unless you went to great lengths to encapsulate everything, there will be several areas where the moisture will penetrate.

There is a reason that camper/RV manufacturers leave an air space between the floor, and insulation/underbelly (which is not sealed 100%).

Your plan can work, but just be aware of the potential issues.

It may be cost prohibitive, but a closed cell pro applied expending insulating foam would solve at least some of the concerns as it is 100% waterproof.

Rob