Any suggestions on what underlayment to use under a floating laminate floor over concrete?

I need to provide some significant shock absorption. I got one suggestion of cork, but that appears to be awfully expensive.

...and cork would not provide what you want from an impact point of view.

Look at http://www.acousticalsurfaces.com/acoust_flooring/images/acoustik.pdf

I got QuietWalk underlayment from Lumber Liquidators, it was $50 a roll for 100 sq ft. I'm putting it down under my engineered hardwood. Not sure how well it works, but I'll know in a week or so.

7/16" OSB over 1/4" panel fold pink foam (4' x 50' bundle). Roof clips hold the sheets together, power nail them down, they won't move. Put your floor down. Very inexpensive, warm, and compliant under your feet.

...and cork would not provide what you want from an impact point of view.

Look at http://www.acousticalsurfaces.com/acoust_flooring/images/acoustik.pdf

Thanks Dennis. I just spoke to them on the phone. It certainly looks like this would do what I want, but it ain't cheap (and what ever is?).

$3/sf + $150 for adhesive.

I'll keep them on my short list.

I got QuietWalk underlayment from Lumber Liquidators, it was $50 a roll for 100 sq ft. I'm putting it down under my engineered hardwood. Not sure how well it works, but I'll know in a week or so.

Hmm, that looks promising. Any idea how think it is?

Would you mind checking back in on this thread and letting us know what you think after the install? I have a LL not too far from me, and was very pleased with their product/service when I bought from them previously.

7/16" OSB over 1/4" panel fold pink foam (4' x 50' bundle). Roof clips hold the sheets together, power nail them down, they won't move. Put your floor down. Very inexpensive, warm, and compliant under your feet.

Does the OSB supply any additional shock absorption value? If I'm putting laminate floating floor over it, would it be ncessary?

As silly as it sounds, I'm trying to preserve every last bit of headroom, and would like to not soak up another ~7/16".

for sound, not shock absorption in a situation where sound isn't a concern.

rubber mat > cork for basically all applications, especially floors that aren't concrete or gypsum concrete (i.e., most floors) where the weight of the rubber mat is a benefit.

pink foams can be cheap, and can be white and yellow and all of those, and they are more resilient than cork, but they aren't without drawbacks relative to rubber mats. Basically, they contain alot of air, and are as such softer and that can lead to a more defined resonance due to the spring effect. and, again, they don't contribute mass.

Brian

Are you saying that 1/4" rigid foam under OSB could cause serious acoustic problems?

I am in a similar situation, where I am trying to plan out flooring options for the basement. My goal is to get off the cold concrete with a minimal effect on acoustics in the HT. I am thinking of using Planton or Dricore but the cost is a little difficult to justify. 1/4" RF would be a lot cheaper, but not if it would be a serious hit to room acoustics.

Thanks
Skipp

Brian

Are you saying that 1/4" rigid foam under OSB could cause serious acoustic problems?

I am in a similar situation, where I am trying to plan out flooring options for the basement. My goal is to get off the cold concrete with a minimal effect on acoustics in the HT. I am thinking of using Planton or Dricore but the cost is a little difficult to justify. 1/4" RF would be a lot cheaper, but not if it would be a serious hit to room acoustics.

Thanks
Skipp

Skipp,

it won't cause problems with sound inside the room, and it will help with higher frequency impact noise, particularily on concrete or something extremely heavy/hard, where high frequency noise is more of an issue.

but, yes, it could cause loss of performance over some freq range due to a resonance. when you put air cavity or something springy into a structure to decouple it, you get this resonance as a side effect. unavoidable reality of the situation.

in this case i think rubber mats with mass + generally less prone to this resonance are a better choice in lightweight floors. in heavy (masonary/gypsum concrete, etc.) floors, the choice of underlayment is less important.

so no, it won't hurt room acoustics, the considerations are only sound isolation. and in situations it can be helpful for that, but its not a universally beneficial product.

Brian

OK, I'm not sure how my question got turned in to an accoustical one.

As I mentioned in my original post, I'm looking for "shock abosorption" for a laminate floor going over concrete.

This is going to be a dance studio for my wife, and concrete is hard on the ol' knees.

Any recommendations from that standoint? I'm thnking seriously about the 1/4" foam from Lumber Liquidators...

Sorry

Didn't mean to hijack your thread.

Skipp

steve,

i also meant no hijacking. :)

with respect to shock absorption, perhaps you could experiment with that foam option under a single board of OSB/drywall and see if it yields the desired results? I am unsure what to recommend other than thicker/softer materials will yield more cushiness.

Brian

I'm looking at Delta-FL. It's supposedly sold at Lowes. I think about $.51 per sq foot.

Good luck

You could use the costco Harmonics (re-branded Quick-Step) underlayment. Its about $30 for a 150 sq/ft roll. Just finished putting down about 800-1000 sq/ft of the stuff and it turned out great!

I'm looking at Delta-FL. It's supposedly sold at Lowes. I think about $.51 per sq foot.

Good luck

I just took a look at their web site... that looks to be interesting stuff, and appears that you can install a laminate floor over the top of it by just using the "laminate foam" included in the kits and not need to install plywood subfloor.

If Lowe's really does sell it for that price. I'll take a good look. Thanks!

You could use the costco Harmonics (re-branded Quick-Step) underlayment. Its about $30 for a 150 sq/ft roll. Just finished putting down about 800-1000 sq/ft of the stuff and it turned out great!

Thanks.. I saw that the other day, and looks to only be 1/8" thick or so... I question how much absorption that would really provide.

Have you used it?

Steve,
If you get info from Lowes, let me know what you find out. I called twice and was on hold for about 15 mins each time and gave up. I haven't made the drive to the store yet.

Scott

So I'm half way done with putting down my floating engineered hardwood with the quietwalk product. So far I really like it... it's a vapor barrier and dense pad built into one product. I used a similar product with my Pergo laminate floor in my last house, but quietwalk seems to perform much better.

Steve,
If you get info from Lowes, let me know what you find out. I called twice and was on hold for about 15 mins each time and gave up. I haven't made the drive to the store yet.

Scott

Sure thing...

So I'm half way done with putting down my floating engineered hardwood with the quietwalk product. So far I really like it... it's a vapor barrier and dense pad built into one product. I used a similar product with my Pergo laminate floor in my last house, but quietwalk seems to perform much better.

Thanks for the report. Are you using this over concrete to provide cushion, or is this over subloor to provide noise attenuation?

If the former, what is your opinion of the amount of "give" the installed system has?

I laid Wilsonart high pressure laminated flooring over concrete. They have 3 different underlayments available. You just want to make sure the underlayment has a vapor barrier when you place it on concrete.

http://www.mairmg.com/wilsonart/homeowner/installation-view.cfm?ID=10

The dealer I purchased through sold me an Armstrong underlayment that was a duplicate of Wilsonarts 2-in-1 pad yet at less cost then the Wilsonart.

I must add that I did not put the laminate in my HT, but installed carpet.

I'm looking at Delta-FL. It's supposedly sold at Lowes. I think about $.51 per sq foot.

Good luck

Following up on this:

Delta-FL is sold at Lowes, it's just that they don't know it. It's a special order item, and they don't have any in store to look at. I was however able to get them to call the manufacturer and request a sample to be sent. When it gets here around the end of the week, I'll go take a look and perhaps order it, as well as report back here what it's like.

For those interested, here is what you can take to Lowe's with you to get them to find it in their systems:

Mfg: Cosella-Dorken
Product: DELTA-FL
Model # 51050
Lowes SOS Item #: 132387

The price is indeed roughly $0.51 sq/ft. It comes in ~6' rolls that cover 328 sq/ft. There is alsoa tape they supply to seam it. It is backes with a moisture barrior.

Lowes also sells QuietWalk, which is ~1/8" thick, an another underlayment that's even slightly thinner. By comparison the Delta-FL is 5/16" thick.

Here is the product website (http://www.deltafl.com/).

Thanks bcrawfo2 for the lead.

Steve,

Curious how your wife's dance floor is working out after 3 years. I looked at this thread and planning to install Delta-FL with laminate flooring on my concrete basement. My goal is very much similar to yours....to provide cushion in the basement for performing dances. I would very much like to hear your feedback.

Parvatha

Hmmmm... just my 2cents.... and I will start by saying I am a big proponent of Delta- Fl and here is why!

I want a real floor feeling for my family room! My house is a bungalow with a walk out basement. The family room is in the basement with concrete floor.

I was also very concerned with height !

I did this room about 8 years ago... at that time laminate flooring was approx $3.00 a sq ft and that was a deal!

But my biggest concern was the feeling a real floor and to avoid the humidity causing cold feet syndrome especailly in a basement where you do not have heating ducts running between the floor joists.

I ended up installing the delta-fl and than laying 5/8ths t&G plywood screwed down into the concrete. Then on top of that 5/16ths parquet. I decided on the plywood so that I had the option of plank flooring. But I was more concerned raising the floor anymore than I had to! So in the one room that is approx 350sq ft. It feels just like a regular floor even has a slight spring to it! Very Nice!
I have the comparison to the rest of the basement which has parquet directly on the concrete... Man that is HARD!!!! So I have never regretted the decision. I have sinced helped my dad install Laminate flooring(much better than what was available 8 years ago) 8mm and while it does a good job... I would not trade my delta-FL floor with the plywood and parquet! Actually neither would my dad... but for him the laminate was a more affordable solution for basement flooring this past year.

So for me I would highly recommend the delta-fl! 8 years later. The finished floor feels the same as it did when it was originally installed.

Thanks for the additional feedback. Sounds perfect for what I need. Did you have any issues with your concrete slab having any bumps/dips in it?

According to the docs, I can install laminate directly over the Delta-FL, so that's the plan.

And as an update with Lowes, 2 attempts to get a sample delivered to the store failed, not sure if the store lost it, or the manufacturer never sent it. As my deadline for installation was looming, I went ahead and ordered a roll (along with the tape that goes with it). It wa due Monday, but didn't make it. Hopefully today.

PS- Costco currently has laminate flooring on sale for ~$1.20/ft with coupon.

Yes, my concrete floor was not perfectly level or flat. It had some undulations in it. Leveling the floor was not an option I wanted to explore. As the room was previously a second kitchen with linoleum tiles.

I decided that the plywood would help even out the floor and in fact it did exactly that!

Now as far as the laminate directly on the delta-fl.... I have to tell you I am not sold on that!

Now I am biased and have the single experience that has worked so well for me!

But the more I think of put the delta FL down and floating the laminate on top of it..... I just cannot imagine it!

In my case the plywood is screwed down to the slab and in fact than compresses the delta-fl but not quite flat. This is how part of the even'ing out takes place for the undulations in the floor.

Now once in a while depending on the season once in a while I come a cross a specific section where if you step just right you hear sort of a dimple being pressed like bubble wrap... but barely audible not loud like bursting bubble wrap. No one else has ever noticed it and it might just be me and my weight.

So the thought of putting the laminate directly on top of the laminate... I just wonder if that is a good thing especially if is intended for specific use like dancing etc.

Now... an engineered wood type of laminate that has a plywood type substrate as part of the flooring... you know the kind that is 1/2" or 5/8's might work better. But I am not sure if the typical 6-8 mm MDF based laminate has enough rigidity if it sat directly on top of the Delta-FL.

Sorry I mised this thread from the begining.

I find it hard to believe that there have been 27 replies so far and no one had mentioned Dricore.

Tom

Dricore.. is that the 2' x 2' stuff they carry at Home Depot.

I have seen it... I have no experience with it or even seeing it installed. One of the things I like about the delta-fl was being able to by a large roll and minimize the number of joints. Also using 4 x8 sheets of plywood or OSB.

The dricore comes with only OSB right?

Having said that... I could see how the Dri core in smaller applications might be easier to handle and put down.

The other thing is the price... Not sure how much the drice core costs per sq ft today... but when I saw it I remember it being a little bit more money than the delta-fl and plywood combined.

Yes, nominaL 2x2. What do you consider "smaller" applications? I've put down 600sf over a day and a half and thought it was extremely easy to work with. The problem I had was that none of my poured concrete wall were straight, so it meant a lot of cutting at the end rows. You would have this same probelm putting down 4X8 plywood. Yes, the surface is OSB, but it is treated and provides a very smooth surface, ready to be covered with just about anything. The sections fit together extremely tight so you don't notice the seams. I haven't priced it lately, but it was very competitive last year.

I guess you can tell I like it. A LOT.
Jeez, the manufacturer should pay me for these endorsements.....

Tom

Sounds like a good product! I can see why you like it!

The only concern for me would have been the OSB. FOR ME... when I was deciding between parquet and plank flooring. I had to go with something that could accomodate either. If I had gone with hardwood plank flooring you cannot(should not) use OSB as sub flooring it has to be plywood to properly nail the plank flooring down. I could have used OSB T&G on top of the delta-FL as well which would have lowered the cost even more than using T&G plywood.

But for me, it had to be plywood.

But the more I think of put the delta FL down and floating the laminate on top of it..... I just cannot imagine it!




Straight from the horse's mouth: Delta-FL Install Instructions (http://www.deltafl.com/bvf/ca-en/service/installation_instructions/below_grade/DELTA-FL_Installation.pdf)

From an article in Fine Homebuilding titled "Finished Basement", I installed 1" thick expanded polystyrene (EPS) rigid foam boards, a layer of 1/2" plywood secured with concrete screws and a second 1/2" plywood layer fastened with drywall screws to make a stronger floor. The foam seams are sealed with expanding foam and seam tape (like the one for house wrap) to prevent infiltration of moist air.

All of this is based on the information from the Building Science Corporation. Makes for a very comfortable and warm floor unlike bare concrete.

Jorge

Straight from the horse's mouth: Delta-FL Install Instructions (http://www.deltafl.com/bvf/ca-en/service/installation_instructions/below_grade/DELTA-FL_Installation.pdf)

Oh I am not saying that it is not what the manufacturer says can be done.... I am just sharing my thoughts after having installed the product in the manner I chose.

I was hoping someone who had actually layed the laminate directly atop the Delta-fl as per the vendors insstructions could have shared their opinions and experience.

In order to round out this thread for the archives...

I picked up my roll of Delta-Fl and sealing tape from Lowes on Friday night, and spent Saturday installing it. As I referred to in the instruction link above, laminate flooring (with it's underlayment) can be installed directly over the top of Delta-FL. Costco had a sale on laminate flooring, so I bought ~340 sq. ft. of that, and 2 of the associated installation kits, which comes with the spacers and tap-blocks, along with 150 sq. ft. of 1/8' foam underlaymnt/vapor barrier.

As it turns out, Delta-FL is not what I expeted... I thought it would be more of a stiff foam, but in reality it's a thin-wall plastic (actually HDPE). It comes in a 5' wide roll, and has ~5/16" tall 'dimples' in it that provide the actual shock absorption.

Laying it is relatively straight-forward, I'll let the previous instructions link provide the detail there. It did tend to want to buckle and ripple a bit on the floor, but I could "walk" the ripples out away from the laminate as the rows were progressing.

With the 1/8' foam on top of the Delta-FL, there's a total ~7/16" of underlayment, with the laminate flooring applied directly on top of it, floating. No plywood/OSB, screws, etc.... just snap the flooring together on top of it (altho getting the floring together was a 12-hour chore in itself).

The end result is fantastic. Just what I had hoped for - a nice surface over concrete that has the feel of a framed floor. After some extensive scientific validation (we jumped around on it a while), it should really fit the bill as a dance-surface for my wife's studio. the concrete pad was not exactly level, but the underlaymeny helps soak some of that up. No odd sounds or feels to speak of.

I'd highly recommend it for applications directly over concrete floor that don't require you to sacrifice a lot of height.

A few pics of it start on page 7 of my site (http://caesare.homeip.net:32171/basement/)

PS- teenie, you said
"In my case the plywood is screwed down to the slab and in fact than compresses the delta-fl but not quite flat. "
I imagine if this is true, you've eliminated much of the value that Delta-FL provides.

Glad to hear it worked ou the way you wanted!



PS- teenie, you said
"In my case the plywood is screwed down to the slab and in fact than compresses the delta-fl but not quite flat.

I imagine if this is true, you've eliminated much of the value that Delta-FL provides.


Not sure what you meant by eliminating much of the the value that delta fl
provides.... It is a humidity/mosture barrier. I installed as per the manufacturers instructions. I was merely trying to point out that the reality is that when you screw down the plywood to the concrete slab that there is some compression that takes place. Again... not quite flat. Meaning the dimples are still in place providing an air gap between the slab and the plywood but slightly compressed.

The only caution I was rasing for you was I did not see how the delta-fl would hold up with just laminate floating on top.

Again, sounds like you are happy with the way it came out which is what matters in the end.

While it is a vapor barrior as well, maintaining the air-gap is an important part of the entire system design, which includes impact resistance, insulation value, as well as vapor management.

From their website (http://www.deltafl.com/) :

This air-gap membrane is made up of a special high-density polyethylene resin (FDA approved), providing a dimpled surface with outstanding compressive strength, impact resistance and long-term performance.

DELTA®-FL is a uniquely dimpled, heavy-duty grey plastic membrane that keeps you and your family warm and comfortable in your basement, or any room in the house with a concrete, slab-on-grade floor. The membrane is installed with its dimples down to create a 5/16-inch thick air space above the slab, and can be covered with a plywood subfloor and topped off with carpet or flooring systems.

with the DELTA®-FL system, the space between the dimples provides a sufficient air-gap to equalize the water pressure above and below the concrete slab.



Furthermore, the installation istructions don't mention anything about screwing any subfloor down so it compresses the material "almost flat". As a matter of fact, several of the installation scenerios allow you to float the subfloor material too, and only recommend a screw in locations where there may be "bounce" because of concrete irregularity underneath.

So, unless you really didn't mean "almost flat", I suspect much of what differentiates Delta-FL from regular plastic vapor-barrior underlayment that is 2-1/2x thinner has been lost.

I'm sure you are happy with it, and that's what counts, but for others looking to use this, I'm pointing out that's not the intended installation method.

Dricore.. is that the 2' x 2' stuff they carry at Home Depot.

I have seen it... I have no experience with it or even seeing it installed. One of the things I like about the delta-fl was being able to by a large roll and minimize the number of joints. Also using 4 x8 sheets of plywood or OSB.

The dricore comes with only OSB right?

Having said that... I could see how the Dri core in smaller applications might be easier to handle and put down.

The other thing is the price... Not sure how much the drice core costs per sq ft today... but when I saw it I remember it being a little bit more money than the delta-fl and plywood combined.

I thought it might help folks to perform a cost comparison between DriCore and Delta-FL / Plywood combination. The cost comparison does not factor any tape and / or glue required for the installation.

Observation: DriCore appears to be a factory-assembled sandwich of Delta-FL and plywood, but appearances can be deceiving.

Prices: DriCore is sold in 2x2 tongue and groove squares at Home Depot ($5.98 each), and Menard's ($4.98 each). Someone mentioned in this thread that Delta-FL equates to $0.51 per SF at Lowe's, so I am going with that cost.

DriCore
2x2 piece = 4SF
4SF x 8 pieces = 32SF

8 pieces x 5.98 each = $47.84 for 32 SF of material from Home Depot ($1.49/SF)
8 pieces x 4.98 each = $39.84 for 32 SF of material from Menard's ($1.24/SF)

Delta-FL & Plywood Combination
4 x 8 piece of plywood = 32 SF
Cost of 23.32 T&G plywood at Lowe's = $19.49
Delta-FL cost is $0.51 x 32 = $16.32 for 32 SF of material

Total cost of 32 SF of plywood and Delta-FL at Lowes is $35.81 ($1.11/SF)

According to my math above (which I think is correct), DriCore is a more expensive route. I don't know which is easier to install, but don't forget that time is money.

I hope this helps others out.

Mark

Dricore does not provide a vapor barrier since it is broken up into squares. Delta-FL is continuous and sealed so that I think that it would be better to prevent moisture infiltration.

Dricore does not provide a vapor barrier since it is broken up into squares. Delta-FL is continuous and sealed so that I think that it would be better to prevent moisture infiltration.

Excellent point. I was also thinking that a bunch of 2x2 T&G squares would not be as sturdy as 4x8 sheets of T&G plywood, but that is probably splitting hairs.

Mark

Excellent point. I was also thinking that a bunch of 2x2 T&G squares would not be as sturdy as 4x8 sheets of T&G plywood, but that is probably splitting hairs.
I've got Dricore down. Feels very sturdy. I think it might be more forgiving of a not-quite-perfectly-level floor because it is 2x2.

Mark-- I'm out in the Fox Valley, down the 59 corridor. Shoot me a pm if you want to see the floor.

Dricore does not provide a vapor barrier
I don't think dricore ever advertised that it was VAPOR barrier, only as "water resistant." However, the tiles fit to gether VERY tight and I think the bottom barrier overlaps when installed correctly.

DriCore is a more expensive route
True, but the top side of the dricore is treated/sealed with something as it is a bit slippery and the plain T&G won't be.

Tom

Steve - do you have another link to the pics? I can't seem to get into your site. I'd like to check out the results of your install. I'm planning on putting down an engineered wood floor (probably about 1/2" thick) on top of the concrete in my basement. I don't have any moisture problems at the moment but fear of moisture has me considering the delta-fl. I'd go the same route you did - install it floating on top of the pad on top of the delta-fl with no subfloor. I don't want to use dri-core because I don't really need a sub floor.

Thanks.

I've had a few people who could not get to my site due to their firewall not being happy with HTTP connections to a port other than 80.

If you can't configure your FW to allow that, PM me your email address and I can send the pics to you.

Steve,

Curious how your wife's dance floor is working out after 3 years. I looked at this thread and planning to install Delta-FL with laminate flooring on my concrete basement. My goal is very much similar to yours....to provide cushion in the basement for performing dances. I would very much like to hear your feedback.

Parvatha

Wel... nothing like a delayed response, eh?

I just came back accross this thread. The floor as been down for ~ 10 months now, and in use regularly for about 8 of those. So far it's been great. It really does well as a dance area to absorb shock. The floating laminate on top has had no issues.

Two thumbs up!

Thanks Steve for resurrecting this thread - and thanks to those who had replied to my new thread about Delta FL.

So are you of the opinion that I could float TiG plywood on top of the Delta? Is there any concern over shifting or creaking?

I plan to put carpet over the top of the TiG; do you put the walls on top of the floor? Or should I frame the walls first?

Thanks in advance
Tim

I think if you take a look at those installation instructions linked earlier in the thread, it addresses how you can lay subfloor over the top if you desire.

As for the walls, they were framed first, and there's a specified clearance (5/16"??) you leave at the wall edge for expansion.

With the floating laminate flooring I bought, I went ahead and used the installation kit for it, and the instructions for it's included moisture barrer (1/8" foam) has you "roll" it up the wall, and then you "capture it" by fastening it to the wall when you put your baseboard on.

Here's (http://caesare.homeip.net:32171/basement/slides/IMG_1871.htm) a shot where you can see the Delta Fl, the additional foam underlayment, and the laminate.

Hi- I read the postings of scaesare with interest regarding his wife's dance floor. My girlfriend and I are also building a dance floor- we were concerned about the "spring" in the floor, the acoustic behavior of laminate, and the durability of the laminate flooring we are using (Ikea's Tundra). Have you had any chipping of the laminate floor due to dancer's heels? If you had any updates, I'd be happy to hear how things have gone.

Thanks.

Woefully late reply... sorry.

Nope, no chipping at all after 18+ months thus far.

I recently installed a floating floor over a Delta FL membrane without plywood. And I’ll try to describe my experience. Of course it works but certain rules should be followed…
1. The concrete subfloor should be well prepared, this is true for all installations method but it’s more important if you don’t use a plywood or OSB because their rigidity dampens the concrete imperfections. So take a 3 feet level or something straight and level with cement any differences that exceed ¼ inch. In my case I only levelled the major imperfections and I regret this time economy.
2. I wanted to be sure the floating floor was to be silent so I installed a geotextile membrane (The kind of thick membrane used in landscape) between the concrete and the FL membrane with a nice success, not very costly and no click sound when walking over the floor.
3. Tape the joints to improve the air tightness.
4. If there is a slight gap in the concrete floor add a small part of Delta FL to level it (Doubling the FL membrane).
5. A common mistake is to use a plank with a broken snap on the side or even on the lengths. The floor contracts and dilate about ½ inch from winter to summer, If many planks are snapped and holds strongly together the contraction will necessarily takes place on the broken snap and the resulting gap will be displeasing.
6. The planks are sometimes made to be installed from left to right and the good side should face the wall, I started the wrong way and found it very difficult to insert the planks so read well the manufacturer instructions. You won’t have to start again.
The pros:
Saves time and money. It gives a medium to good result.
The cons:
The concrete sub floor has to be levelled more.
There is more swing in the finished floor without the plywood or OSB.

Why to use this membrane? Gives a protection against little water infiltration, like a leaking water heater, it will go under the wood floor without destroying it. The membrane is resistant to pressure, in fact it’s more resistant than the planks, so the planks will break before the Delta FL crush.
Between the planks and FL I used laminated foam, it’s good but not resilient and easy to flatten, it doesn’t come back to its position after flattening. I have grand piano, about 500 pounds, it’s supported on three legs, that’s 165 pounds on each legs so to limit the pressure on the planks I bought three 8x8 inch iron plate. Otherwise it was too much for the planks. If you have heavy furniture’s think about putting something under it.

Sylvain