JIMMIE wrote in news:e8e110ba-6d39-4af6-b981-
:

I started replacing the siding on a pickup bed camper and when I got
the siding stripped down I found the fiberglass insulation was not in
the best shape. I was thinking of trying one of the DIY kits of
polyurethane spray in insulation instead of putting back more
fiberglass batting. Ive read the brochures but I wondered if anyone
has had any first hand experience using it. It looks to me like you
just keep spraying in thin layers , let them expand and set then do it
again to you get the thickness you want. I was looking for the
gotchas. My plan is to set the tanks up on a work table with casters
and have the wife push it around the camper following me. Hopefully
once we start we can just keep going until its done. Since the
framing is 2 X2 I figure two passes should be enough.

Jimmie


The stuff is great but a pain to work with. It expands with a very lumpy
surface so it is impossible to get a flat surface. You have to trim it down
to get it flush with the 2 x 2's. You get large hills and deep valleys
which means you go back to fill in the valleys and then you end up with a
lot of hills to trim off. I got a trimmer from a friend but I don't know
what it is called. It was a lot of work to do it manually - sort of like a
coarse sanding/grinding job. I saw a TV show where they used a power
trimmer it seemed to be fast and simple.

If you want to save a lot of work you could put in the inside panels
partway up and spray down into the space. The problem with this is that the
foam expands instantly with enough force to blow a panel loose. You have to
spray with the trigger down for just a split second and keep the nozzle
moving very rapidly. You add thin layers into the space to keep it from
being blown apart. Saves a huge amount of trimming. I was helping my Dad
insulate a small hot tub shed. We put cheap panels as horizontal strips
about 18" high, insulated behind them and then put good panels on top for a
finished surface. The foam acts like a good glue and we at first tried to
get the cheap panels off to re-use them but they just stuck to the foam and
tore and were too much trouble to remove so we left them.

We made three practice boxes to practice spraying down into a space and
learn the trigger action and nozzle swing that wouldn't blow the panels
apart. First two trials we blew the panels apart but by the third try we
figured it out. The top space we had to just spray it on and trim it off -
took a lot longer to do the top 18" strip than the rest of the walls.
Ceiling was easy because we sprayed from the top before nailing on the roof
sheeting and we left the foam rough.