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Discussion Starter #1 (Edited)
Probably has been answered before, but could not find any thread about it.

I want to insulate the floor and can not decide on the sandwich thus hoping for some assistance.

My original plan was to do like this:

  1. Metal with 2" underlayment planks in the gaps
  2. Reflectix (attached with great stuff foam)
  3. 1" Polyiso (attached with 3m 90 spray)
  4. 1/2" Plywood (attached with 3m 90 spray)
  5. Some floating floor laminate

The reason I was going to put reflectix is sound insulation, but not sure if it actually provides much. Is there anything better? So now I am thinking about this sandwich below:

  1. Metal with 2" underlayment planks in the gaps
  2. 1" Polyiso (attached with great stuff foam)
  3. 1/2" Plywood (attached with 3m 90 spray)
  4. Some bubble underlayment
  5. Some floating floor laminate

Perhaps you folks have any suggestions?
 

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I'll share how I did mine and why...

I apologize for the large pictures up front, I'm linking to images I already uploaded so no thumbnails (these don't count against the stored file size limit).

Commercial floors are glued in, folks who had to remove them ended up splintering the plywood to get them out - I wanted mine to be removable. There will be a lot of movement from expansion and contraction as well as road vibration plus the chance of moisture instrusion so I personally would not go with foam as the structural adhesive in this case. I also did not want the foam-board under the flooring in case I had to shift pallets or large loads that would cause the fasteners to stand proud and catch on thing if the foam gave way beneath or the floor dented from two, three days or more heavy load bearing creating new soft spots.

Prodex gap planks : Black EPDM Rubber Roofing : 1/2" plywood (primed 3 coats)

Reflectix is transparent to sound and the air spaces can/will go flat in time. Instead of foil/bubble/foil I went with foil/foam/foil _Prodex_, this source has two-for-one sales that take the bite out of the price. Prodex cuts high frequency sounds well AND has a million other uses, as custom window glass sun guards it withstood years of being tossed around and used in my F-150 pickup. Without all the reflective insulation gimmicks the Prodex provides an honest R-0.7. The Prodex batten strips are glued in place with 3m 90 spray adhesive.

I added the EPDM roofing to soak up sound and keep the floor squeak free. And just because I had some on hand I used 0.063" silicone mat for the section above the exhaust catalyst/muffler, more in case of a small grass fire or road hazard debris igniting than any real hazard present from the factory.

The 1/2" plywood worked well so far, with it primed/painted there is no moisture warping or lifting edges and i don't fear accidentally leaving a door open in the rain quite so much. I used a mix of grain elevator conveyor belt bolts and 1/4" self-tapping floor screws, drill undersized and let the screw expand the metal for best strength. Eventually I collected all the tools & odd bits to use rivnuts where the screws went in the flooring, before the built-ins are installed I'll pull the floor and upgrade them.

Putting the foam above the hard flooring made it easier to stay comfortable with less mass to have to heat. This winter I traveled and slept in the van as a big metal tent; I tossed in leftover 1-inch polyiso foam and laid foam rubber mats and carpets over the polyiso and it was barely adequate - we've got harsh winters. When it comes time to finalize the floor insulation it will probably be 1-inch but 1-1/2" foam would make it more pleasant, and will top the foam with 1/4" plywood glued to it to protect it. Others have said here that one thing they'd do differently would be more floor insulation but perhaps they were not six-foot two-inches tall..

Anyhow, that is just one way out of a thousand...




 

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Sound insulation is most important on the thin side panels and aft wheel wells. The floor itself is very stiff and strong due to the ridges. A rigid inside floor and thermal insulation system should be all that is necessary for sound from below.

Here is what I did: I removed the D-ring cargo tie downs and procured longer bolts with the same metric threads. I used luan over the ribs without filling in the spaces between the ribs as the trapped air itself provides some insulation. (Not filling rib spaces saves a huge amount of work.) On top of that I used a semi-rigid plastic insulation half an inch thick. Reflectivity is not necessary here as there is no radiant heat from sun light. On top of that I used 5/8 inch quality plywood. Large fender washers and the bolts into the D-ring locations did some of the holding down especially along the edges.. Drill a small pilot hole from underneath up to get the locations and then a slightly oversize hole from the top down. For hold downs additional to the former D-ring locations especially in center areas (and across the front and rear) I used about 18 #12 , 2 and 3/4 inch TEKS self drilling, self tapping screws from Home Depot.

These special flat head screws are designed for attaching wood to metal. They have ears on the upper side of the drill point. As they go through the wood/insulation/luan they make a hole slightly bigger than what will be needed in the metal. When the screw drill point goes through the metal floor the ears break off and the screw advances and self-taps and threads into the metal. As the screw drills and then tightens there is no "jacking" of the wood up away from the metal as their are no threads cut into the wood/insulation/luan. All is pulled down tight. Before installing each screw I drilled the counter sink for the flat head as the screws cannot be removed and successfully reinstalled. Also be sure to check under the van to be sure you are not going to hit a critical part with any exposed length of screw.

At doors the exposed floor edges were dressed with aluminum angle. For final floor surface I used the black hard plastic cargo mad that I had ordered with the van. This was originally loose in the van and I removed it and used it as a pattern to cut the luan/insulation/plywood parts with staggered joints. Interior stuff was screwed down through this into the 5/8 inch plywood and that was all needed to hold the mat in place. Any other floor surface could be installed over the plywood.
 

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I have flooring between the modular cabinets only as the cabinets can then not slide forward in an event. It floats over .5 inch polyiso sheets. And can be removed with the insulation. It is held flat by a few trim strips on the cabinets which themselves are held down with washers and bolts of the D rings. It is topped with fitted disposible carpet to form a nice warm floor, easily removed and renewed when needed. The best feature of this is the added safety for a crash. Attaching the cabinets directly to the van adds to the safety.
 

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I used 1/2" Minicell closed cell foam on the bare metal floor then added my plywood. I haven't decided what's going on top of the plywood yet.
 

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Reflectix is likely to be near worthless squished in the floor. Same for Prodex or any similar material. It really needs an air gap of at least some space to do much work.

Polyiso in the floor seems to be a good way to go though.



I followed the design from Dave on the Sprinter forums. Started with a layer of minicell closed foam. Filled the gaps and then a layer on top. Top that with 1/2" plywood, held in place by the tie down bolts. On that I have a framework of 80/20, which is 1.5" thick. In between, on the plywood, is 1" of polyiso foam, 1/8" ABS plastic sheet to spread weight loads, and then 3/8" of heavy rubber mat on top. The rubber mat has been great. Its a bit hard to keep clean, but the feel is great, definitely helped with the sound dampening, and best of all stuff doesn't slide around on it.


I'm getting a bit of squish of the polyiso from point loads. Putting it under plywood would mitigate that problem quite well.
 

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Sound insulation is most important on the thin side panels and aft wheel wells. The floor itself is very stiff and strong due to the ridges. A rigid inside floor and thermal insulation system should be all that is necessary for sound from below.

Here is what I did: I removed the D-ring cargo tie downs and procured longer bolts with the same metric threads. I used luan over the ribs without filling in the spaces between the ribs as the trapped air itself provides some insulation. (Not filling rib spaces saves a huge amount of work.) On top of that I used a semi-rigid plastic insulation half an inch thick. Reflectivity is not necessary here as there is no radiant heat from sun light. On top of that I used 5/8 inch quality plywood. Large fender washers and the bolts into the D-ring locations did some of the holding down especially along the edges.. Drill a small pilot hole from underneath up to get the locations and then a slightly oversize hole from the top down. For hold downs additional to the former D-ring locations especially in center areas (and across the front and rear) I used about 18 #12 , 2 and 3/4 inch TEKS self drilling, self tapping screws from Home Depot.

These special flat head screws are designed for attaching wood to metal. They have ears on the upper side of the drill point. As they go through the wood/insulation/luan they make a hole slightly bigger than what will be needed in the metal. When the screw drill point goes through the metal floor the ears break off and the screw advances and self-taps and threads into the metal. As the screw drills and then tightens there is no "jacking" of the wood up away from the metal as their are no threads cut into the wood/insulation/luan. All is pulled down tight. Before installing each screw I drilled the counter sink for the flat head as the screws cannot be removed and successfully reinstalled. Also be sure to check under the van to be sure you are not going to hit a critical part with any exposed length of screw.

At doors the exposed floor edges were dressed with aluminum angle. For final floor surface I used the black hard plastic cargo mad that I had ordered with the van. This was originally loose in the van and I removed it and used it as a pattern to cut the luan/insulation/plywood parts with staggered joints. Interior stuff was screwed down through this into the 5/8 inch plywood and that was all needed to hold the mat in place. Any other floor surface could be installed over the plywood.
Your method is by far the best, most reasonable one I have found so far. People try to overthink things way too much sometimes and most of these floor modifications highlight that to the extreme.
 

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An addition to my post 3 above in light of post 8 just above. I had determined that my interior design would not use the tie down locations as my interior stuff needed far more attachment points and in different locations. Many, many screws into the 5/8 inch ply would be far better. Because of this I omitted any type of D-rings. The bolts and fender washers at the former tie down locations stand proud as the bolts have hex heads above the ply floor. Their location, however, for my layout was in every case near the sidewall and under furniture, etc.
 

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Anyone put the insulation right on top of the factory floor?

To minimize work, I was going to put 1/2'' polysio right on top of the factory floor with great stuff as an adhesive then 1/2'' plywood on top of that. I'm planning on having a furnace so figured I could get away with 1/2'' insulation, save the space for roof height, and pay more in heating costs.

I also need to figure out how to install the furnace without ripping up the factory floor too. Anyone done that? P.S. I'm a new at this.
 

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I found Sprinter tie-downs readily available on eBay. They are much more attractive for where it shows, and the whole assembly is virtually flat with the floor surface.
MsNomer - I'm trying to find these tie downs on ebay. Are they black or did you paint them. I'd like to use them to secure my dog's crate as we travel. Thanks!

EDIT:
Found them! However, it is the UK ebay (contacted seller to see if they ship)...did you find them via US ebay?
http://www.ebay.co.uk/itm/6-GENUINE...233746?hash=item2ef5f906d2:g:IqkAAOSwImRYCHun
 

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When I was designing my builder I researched reflective's and learned that you have to have an airspace for it to be effective sandwiching it between the floor seem like a waste of money. This is what I did and I like it very well it's warm and very quiet. I used three 3/4" closed cell insulating foam board, three 1/4" laun plywood and rubber backed carpet. I bought it all of it at Lowe's for around $300, I like using carpet because hard surface, always looks dirty and it is cold to touch when you walk around with no shoes.
 

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PopeAng, yes I did find them on US eBay--several times in fact, because I first bought just the ones that showed, then went back and bought the rest. I had my choice of several listings. Perhaps I just got lucky. However, I would not hesitate to buy from eBay UK if the price is right. Just the other day I got a package that shipped from London in two days!! My package from Michigan is taking nearly a week.
 

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PopeAng, yes I did find them on US eBay--several times in fact, because I first bought just the ones that showed, then went back and bought the rest. I had my choice of several listings. Perhaps I just got lucky. However, I would not hesitate to buy from eBay UK if the price is right. Just the other day I got a package that shipped from London in two days!! My package from Michigan is taking nearly a week.

Thanks. I did go with the UK seller. Shipping was nearly as much as the tie-downs, but they look so nice - finishing touches. I assume you where able to use the screws it came with....how thick is your floor? Mine will be ~2"
1" foam board
1/4" closed cell foam sheet
3/4" plywood
vinyl/linoleum sheet 1/8" (?)
 

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IIRC, you will need new longer bolts. Also, IIRC, MB and PM use the same bolt but it is not a common thread, so take an original to a real hardware store. We used a stack of stainless steel washers to fill in, being very careful not to lose one.
 

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Reflectix is likely to be near worthless squished in the floor. Same for Prodex or any similar material. It really needs an air gap of at least some space to do much work.

Polyiso in the floor seems to be a good way to go though.



I followed the design from Dave on the Sprinter forums. Started with a layer of minicell closed foam. Filled the gaps and then a layer on top. Top that with 1/2" plywood, held in place by the tie down bolts. On that I have a framework of 80/20, which is 1.5" thick. In between, on the plywood, is 1" of polyiso foam, 1/8" ABS plastic sheet to spread weight loads, and then 3/8" of heavy rubber mat on top. The rubber mat has been great. Its a bit hard to keep clean, but the feel is great, definitely helped with the sound dampening, and best of all stuff doesn't slide around on it.


I'm getting a bit of squish of the polyiso from point loads. Putting it under plywood would mitigate that problem quite well.
Would like to know if this is the proper Polyisocyanurate http://www.homehardware.ca/en/rec/i...-Foam-Insulation/_/N-ntht4Z1z141g9/R-I2719407 to use for under flooring ? 3/4 inch Polyisocyanurate plus 3/4 inch plywood on top , no glueing all held down by tie down bolt and future cabinets .
 

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Reflectix is likely to be near worthless squished in the floor. Same for Prodex or any similar material. It really needs an air gap of at least some space to do much work.

Polyiso in the floor seems to be a good way to go though.



I followed the design from Dave on the Sprinter forums. Started with a layer of minicell closed foam. Filled the gaps and then a layer on top. Top that with 1/2" plywood, held in place by the tie down bolts. On that I have a framework of 80/20, which is 1.5" thick. In between, on the plywood, is 1" of polyiso foam, 1/8" ABS plastic sheet to spread weight loads, and then 3/8" of heavy rubber mat on top. The rubber mat has been great. Its a bit hard to keep clean, but the feel is great, definitely helped with the sound dampening, and best of all stuff doesn't slide around on it.


I'm getting a bit of squish of the polyiso from point loads. Putting it under plywood would mitigate that problem quite well.
Checking to see if i have right type of polyiso for my floor http://www.homehardware.ca/en/rec/i...-Foam-Insulation/_/N-ntht4Z1z141g9/R-I2719407
i will use 3/4 inch polyiso with 3/4 inch plywood on top , all held down by tie down points and future cabinets .
 

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Yup that should be fine.
 

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IIRC, you will need new longer bolts. Also, IIRC, MB and PM use the same bolt but it is not a common thread, so take an original to a real hardware store. We used a stack of stainless steel washers to fill in, being very careful not to lose one.
The original bolt is an M8-1.25. Buy the length based on the depth of all flooring layers used. I went with 65mm length.
 

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The original bolt is an M8-1.25. Buy the length based on the depth of all flooring layers used. I went with 65mm length.
Perfect timing! I'm about to need some myself. I'd like to use one of them as electrical ground. Should I do anything to improve electrical conductivity? Otherwise it's just bolt threads for contact. Perhaps a thick steel sleeve/spacer around the bolt?
 
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