Ram Promaster Forum banner

Advice on XPS Subfloor Squeaking

858 Views 22 Replies 12 Participants Last post by  Smokymtgirl03
Hi everyone. I’m in the early stages of converting a 159”. Currently working on the subfloor. The floor squeak is driving me nuts. Almost every location on the floor has some amount of squeak when stepped on, even after a couple rounds of trimming & shaping. Video attached. Any ideas? I'm on the verge of abandoning the foam-only layer and laying wood framing. Thanks for your help.

Video: Promaster XPS Floor Squeaking Example

Based on various threads in the forum I went with the following:
  • 1/2” ACX Plywood over 1” XPS
  • Cut & painted both sides of plywood the same day to try and minimize warping (still seems to be a light bow)
  • Did not fill the 0.30” floor channels, or adhere the layers together.
-1/4”+ gap between floor and all vertical surfaces
  • Small wood supports at slider and rear door openings.
  • Used M8 bolts at flat washers at factory tie-down locations.
  • Taped all XPS butt joints using foil tape.

Motor vehicle Automotive tire Automotive design Gas Auto part
Motor vehicle Automotive tire Vehicle Mode of transport Automotive design
  • Sad
Reactions: Bruce in NOLA
1 - 20 of 23 Posts

· Premium Member
2016 3500 ext-ht
Joined
·
1,350 Posts
Hi everyone. I’m in the early stages of converting a 159”. Currently working on the subfloor. The floor squeak is driving me nuts. Almost every location on the floor has some amount of squeak when stepped on, even after a couple rounds of trimming & shaping. Video attached. Any ideas? I'm on the verge of abandoning the foam-only layer and laying wood framing. Thanks for your help.

Video: Promaster XPS Floor Squeaking Example

Based on various threads in the forum I went with the following:
  • 1/2” ACX Plywood over 1” XPS
  • Cut & painted both sides of plywood the same day to try and minimize warping (still seems to be a light bow)
  • Did not fill the 0.30” floor channels, or adhere the layers together.
-1/4”+ gap between floor and all vertical surfaces
  • Small wood supports at slider and rear door openings.
  • Used M8 bolts at flat washers at factory tie-down locations.
  • Taped all XPS butt joints using foil tape.

View attachment 93319 View attachment 93320
The squeak will go away once you lay the ply and bolt it down, let the ply relax and finally putting the weight of your build on the ply.
 

· Registered
Joined
·
1,040 Posts
It's been a very long time since put my floor down, but I have a similar setup to yours except with 3/4" ply, no paint and no wood filler by the edges. If I remember correctly I added a small number of rust resistant self tapping screws here and there on the floor to make sure it was 100% secure.

One thing I would suggest is adding a piece of PVC conduit (Or a couple) in the floor while it's still possible. Not doing was a big regret of mine as running wires from one side to the other became complicated later on.
 

· Registered
2017 Promaster 2500 159 HT Gasser
Joined
·
502 Posts
Once you put your cabinets, etc. in it will reduce if not eliminate these creaks. Plus with no insulation in it magnifies even the smallest creaking noise. I used wood nuts to thru bolt with a washer to add 2 or 3 securing points on the plywood at the joints and perimeter between the tie down points. I believe now only 1 between the tie downs would have been enough.
 

· Registered
2021 PM 159 HR - Los Angeles, CA
Joined
·
96 Posts
+1 about the squeaks reducing after you tighten everything down. Are you sure the wood fillers at the rear door and sliders are shorter than the thickness of the compressed XPS? If they are holding the plywood higher they could cause it to "float" a little and that could cause some squeaking.
 

· Premium Member
2014, 138WB, High Roof, Gas, SW MT
Joined
·
3,305 Posts
Hi,
The video is awful - there has got to be a way to improve that a lot.

You could glue the layers together.
My floor is 1 inch polyiso with 1/4 inch plywood over it - all glued together. Never had even a trace of a squeak.
Full details here...

I don't think that the strips I used to fill in the spaces between the floor ribs are necessary - I would leave them out if doing it again.

Gary
 

· Registered
Joined
·
1,040 Posts
Just a guess, but I'm wondering if the noise may be originating between the painted plywood surface and the foam? :unsure:

The paint does appear to have a bit of a glossy finish and might be "grabbing" the surface a bit. Happen to have any wood dust handy from cutting the boards? Or even some flour? Try dusting the surface between the two materials and see if the noise might dissipate.
 

· Premium Member
2016 3500 ext-ht
Joined
·
1,350 Posts
M
Just a guess, but I'm wondering if the noise may be originating between the painted plywood surface and the foam? :unsure:

The paint does appear to have a bit of a glossy finish and might be "grabbing" the surface a bit. Happen to have any wood dust handy from cutting the boards? Or even some flour? Try dusting the surface between the two materials and see if the noise might dissipate.
Mold food.
 

· Registered
Joined
·
7 Posts
Discussion Starter · #10 ·
Thanks everyone for the responses. To test the "painted plywood rubbing on XPS" I removed the back plywood sheet and added a layer of scrap fabric I had laying around. Squeaking reduced by 80%, even without bolting the sheet back down through the tie-down locations.

Any ideas on what to use as a permanent 'fabric layer' that doesn't invite mold growth? Some ideas:
  • Thin Underlayment foam
  • Painter's plastic tarp
  • Landscaping fabric
  • Just glue the plywood down to the XPS sheets, hope it works?

Otherwise I could redo all of the plywood sheets and try a different waterproof coating, but hoping for an easier and cheaper solution.

Motor vehicle Vehicle Automotive tire Automotive exterior Fixture
 

· Registered
Van #2 2021 EXT
Joined
·
6,173 Posts
IMO;

You might get less squeaking with;
  • Polyiso rather than 15psi XPS
  • Coating & letting cure the bottom of the plywood with a more slippery cured coating
  • Placing say 6mil poly on top of the XPS & under the plywood
  • Placing a 6mil poly on top of the van metal floor & under the CPS
  • Thicker plywood & different plywood (I use 3/4” 13laminate layer Russian Birch)
  • Different higher compression strength XPS
 

· Registered
Van #2 2021 EXT
Joined
·
6,173 Posts
Thanks everyone for the responses. To test the "painted plywood rubbing on XPS" I removed the back plywood sheet and added a layer of scrap fabric I had laying around. Squeaking reduced by 80%, even without bolting the sheet back down through the tie-down locations.

Any ideas on what to use as a permanent 'fabric layer' that doesn't invite mold growth? Some ideas:
  • Thin Underlayment foam
  • Painter's plastic tarp
  • Landscaping fabric
  • Just glue the plywood down to the XPS sheets, hope it works?

Otherwise I could redo all of the plywood sheets and try a different waterproof coating, but hoping for an easier and cheaper solution.

View attachment 93366
Timing ,,, I was writing my above post when you posted this one;

Watching your video, my thought was the coating you used on the bottom of your plywood was “grabbing” your XPS especially as you have 1/2” plywood & it has lots of deflection. If you have a gap all around so there is no vertical surface rubbing, your sound is caused by friction between the xps & plywood (also possible between the xps & van metal floor). As you are point loading the xps to van metal floor peaks & the XPS you used is 15psi, there could be a slight “crushing” sound, but what I heard was “gripping” of plywood to XPS.

The fix in my mind, would be 6mil UV Poly (it is used under concrete floors). Under the plywood & again under the XPS if the under plywood does not resolve the issue.

or Glue the XPS to the bottom of the plywood

& / or glue the XPS I used to the bottom of the plywood ( 30psi & different brand ) all XPS is not the same.

It is best to have “staggered joints” XPS to Plywood, & I was unsure if that was any contributing part of your noise ,,, did not look like it.


The XPS I have had good results with ( 30 psi );

Font Wood Rectangle Electric blue History
 

· Registered
Joined
·
3,885 Posts
I agree, it could be the paint, and it should quiet some when loaded. Gluing the layers together is the most sure-fire solution. It doesn't need to be continuous. A grid of spots should stop any shifting and rubbing.
 

· Registered
Van #2 2021 EXT
Joined
·
6,173 Posts
Also ,,, When you “taped butt joints” on the XPS ,,, What is that?

Did you tape both of the 1” edges where the XPS butt together? Or did you only top surface tape the XPS once it was installed on top of the van floor?

If you are wondering why, take a couple of scrap pieces of XPS & rub them together on the raw butt joint edges.

The foil tape “both edges” rubbing against each other will be basically silent ,,, raw XPS edges rubbing - not so much.
 

· Registered
Joined
·
1,040 Posts
Just dulling the paint with some light sandpaper or Scotchbrite pad would probably work. Another option would be to use thin double sided tape. It doesn't need to be strong enough to hold it together, just keep it from shifting.
 

· Premium Member
2014, 138WB, High Roof, Gas, SW MT
Joined
·
3,305 Posts
Hi,

Any ideas on what to use as a permanent 'fabric layer' that doesn't invite mold growth? Some ideas:
  • Thin Underlayment foam
  • Painter's plastic tarp
  • Landscaping fabric
  • Just glue the plywood down to the XPS sheets, hope it works?

I'd pretty much guarantee that gluing the plywood to the XPS would stop squeaking at that interface, but if its also squeaking where the XPS meets the metal floor, it won't stop that.

Gary
 

· Registered
Van #2 2021 EXT
Joined
·
6,173 Posts
Hi,

Any ideas on what to use as a permanent 'fabric layer' that doesn't invite mold growth? Some ideas:
  • Thin Underlayment foam
  • Painter's plastic tarp
  • Landscaping fabric
  • Just glue the plywood down to the XPS sheets, hope it works?

I'd pretty much guarantee that gluing the plywood to the XPS would stop squeaking at that interface, but if its also squeaking where the XPS meets the metal floor, it won't stop that.

Gary
I see it the same ,,, if the squeaking is between the bottom of plywood & XPS, gluing those 2 products together will stop it. If the edges of the XPS butt joints are not taper I would apply foil tape to them before gluing to the plywood.
 

· Registered
2021 3500 extended in Michigan
Joined
·
365 Posts
I used the same XPS insulation and had a lot of squeaking at my cut edges where they rubbed against anything. I covered the edges with two layers of packaging tape and the squeaks went away. I don't recall whether I did anything to the tongue and groove edges but any raw cut edges in close contact made a heluva noise.

I covered the XPS with 1/2" plywood which got an oil based polyurethane finish on both sides as well as the edges before installing.

FWIW, I had some old pieces of XPS laying around from years back and those pieces had what looked like a plastic finish from the factory that prevented squeaks. The new stuff isn't always the best stuff.
 

· Registered
Joined
·
7 Posts
Discussion Starter · #20 ·
Thanks everyone. I think gluing the XPS to the ply would work, but if it didn't I'd end up with a mess that was both glue-y and squeaky. So I decided to go with @RVR8's suggestion and cut a full sheet of 6mil poly to lay on top of the XPS. The floor is now almost completely squeak-free, I'm happy.

I wouldn't repeat the 6-mil poly if I didn't have to. If I could restart the floor, I'd use:
  • 1/2" baltic birch plywood with oil-based poly (The ACX started to bow my best efforts to lay it flat and work quickly)
  • 1" XPS foam (I'm happy with the 15psi Lowe's stuff, can walk directly on it without noticeable dents)
  • Leave a 3/8" gap all the way around the perimeter
  • Small wood supports at slider & rear door openings
  • M8 bolts and flat washers at factory tie-down locations
  • Foil tape all XPS seams, both taped edges and taped joint
  • Stagger XPS / plywood seams

Thanks again.

Automotive tire Motor vehicle Wood Gas Automotive exterior
 
1 - 20 of 23 Posts
Top