laminate over rigid foam insulation

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  #1  
Old 10-08-07, 11:57 PM
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laminate over rigid foam insulation

Is it acceptable to install floating laminate flooring over 1" rigid foam insulation? My desire is to create a warm subfloor over an existing concrete slab (above grade) as I live in a cold climate. I have already purchased and installed Delta-FL underayment on the slab as a vapour barrier. I was going to just roll out a layer of that approved thin laminate underlayment foam and then float the laminate over top of that, but that will not provide the insulating value I desire. So, my revised plan is now to float a sheet of 1" rigid expanded polystyrene foam (EPS) on the Delta-FL to add an R-value of 3.75 and then install the finished laminate flooring directly over top of the foam. This would all be as a 100% floating system with no strapping, sleepers or plywood of any kind.

My concerns are:

(1) Will the floor feel too "springy" when treaded on? Should I drive a few concrete fasteners through the foam with 1" washers to hold it down tightly to the concrete before laying the laminate?

(b) Will the structural integrity of the laminate be compromised under loads since it is not directly supported by the typical OSB plywood layer that is commonly used? I recognize that laminate should not be layed over carpet for this very reason. However, EPS foam offers quite a bit more compressive resistance than carpet. As a test, for example, if I push down on the edge of a single piece of laminate on carpet you can see it move down quite a bit. If I do the same test with laminate on the 1" EPS foam, it doesn't appear to budge at all due to the even distribution of load. I would prefer not to lay plywood on top of the EPS foam if it is not strictly required from an engineering and design perspective for my proposed plan.

Thanks for any comments!
 

Last edited by vwmaker; 10-08-07 at 11:59 PM. Reason: typo
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  #2  
Old 10-09-07, 05:37 AM
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Wow, I think your concerns are justified.

My advise is call the laminate floor manufacturer and ask them directly. Regardless of their answer, ask them if they will they warranty the product if installed in this manner. Will they put it in writing ? If not, then its a pretty good indication that the propsal is a bad idea.
 
  #3  
Old 10-09-07, 09:32 AM
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What you propose to do will void manufacturer's warranties. If a cold floor is a concern, radiant heat can be installed under laminate.
 
  #4  
Old 10-21-07, 06:05 AM
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I am no expert on this stuff but would you not risk spot compression on the EPS foam over time? I would think the foam would begin to compress in high load or high traffic areas.

Unless this foam is considered weight bearing, I would not think this would be a good idea.

Just a thought, as I have no experience with this application.
 
  #5  
Old 10-21-07, 08:33 PM
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manufacturer's feedback

FYI, here's a followup. The laminate manufacturer said my proposal will put too much strain on the tongue and groove due to the foam compressing. They said a layer of 3/8" OSB on top of the foam will provide an adequately supported platform for the laminate. So, my modifed layout will be: Delta-FL, EPS foam, 3/8" OSB, 3/32" underlayment foam, laminate. After the OSB's down I'll see if the subfloor is too springy, If so, I'll suck it to the slab with some concrete fasteners before putting the laminate down. Total R value approx 5.0. Total thickness about 1 7/8". This is 50% better performance than the best 2x2' pre-manufactured subfloor system available and will cost 40% less. Hope it works well!
 
  #6  
Old 09-18-13, 03:17 PM
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resutls?

How did it turn out?
I have a similar situation and was thinking of doing the same as you.
 
  #7  
Old 09-18-13, 03:28 PM
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Neewest, welcome to the forums! 7 years is a long time. Hopefully all went well, but most of the posters in the thread are inactive.
 
  #8  
Old 09-18-13, 04:11 PM
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@neewest:

It turned out great! I installed the subflooring exactly as I described in my post above, with the addition of Tapcon concrete screws. The floor is very warm, and is not springy to walk on, and I would do it again in future projects if needed. A fair bit of work, but worth it for the superior performance and cost savings over pre-made tile subfloor systems.

The key, for me, was: (a) use many fasteners to hold the sandwich tight to the concrete (so, lots of concrete drilling required! 6-8 per 4x8 sheet), and (b) make sure to shore up any concrete unevenness beforehand underneath (I shimmed with tar paper as needed directly on top of the concrete).

Next time I'd be tempted to spend the extra $ on real plywood instead of OSB, for the greater structure rigidity it offers. Overall, I'd recommend this solution to others.
 
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Old 09-18-13, 05:28 PM
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vwmaker, glad you were still subscribed to the thread. Good information.
 
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