I have a 4 lb. 3 in. Memory foam topper. it is comfortable for us on a blow up mattress and on an old one sided mattress turned upside down. I imagine it would even be okay for us if we put it on the carpeted floor (maybe not). I want to turn it into a mattress by buying a piece of base foam to put under it. I am looking at foamorder.com for a 7 in. piece of polyfoam. Duraflex D30 and D40 both look good because they are between 4 and 5 hundred. They are both 2.5 lbs. D30 says firm with an ild of 30 and D40 says very firm with an ild of 40. I think either would probably be fine for comfort, but would they both also work for edge support? Would they both be considered HR polyfoam because they are above 2.4?
Also, where could I find a 10 in. Mattress case for the custom mattress?
Phoenix, you can disregard the other questions…Would a 5 in. Duraflex D30 from foam order work as a base for our memory foam topper? I think I have settled on that… Ild of 30 and 2.5 lbs/cuft of polyfoam for the base and 3 in. 4 lb. Memory foam for comfort layer…I think it has an ild of 9-11.
Yes, probably not so comfortable on the floor! The 3 lb density is lower than I recommend for a memory foam topper (4 lb) so realize that in a component system it may have a shorter comfort life and may require replacement sooner, but since you’ve already purchased the topper I would not replace it until it becomes uncomfortable for you. If you do end up replacing it in the future, you may wish to consider a memory foam topper that is 4 lb or above in density.
Both of the DuraFlex polyfoam cores you listed are 2.5 lb density, but the compression modulus isn’t listed (needs to be above 2.4, plus density above 2.5 lb to be technically considered high resiliency polyfoam). The EverFlex is listed as high resiliency on the foamorder web site, but not the DuraFlex. You’d want to phone them to confirm before placing an order. A popular ILD for polyfoam cores for many of the simplified choice mattresses is in the mid-30 range, so you’d probably be better off using the D40 versus the D30 in most cases, especially using 4" of plush memory foam on top of the support polyfoam core. But this is a general statement and your individual preferences of course are most important, and I would phone foamorder and explain to them your proposed configuration and ask their advice as well.
Regarding edge support, most polyfoam core mattresses don’t need or use a specific edge reinforcement system, as thicker polyfoam cores of higher ILD and density can provide reinforcement to the edge that is similar, or even superior, to many polyfoam edge systems used in similar mattresses. There is more detailed information about edge reinforcement systems in post #2 here.
Besides the site you are considering for your polyfoam core, you can also take a look at the listing for mattress covers in the component thread here. Many offer covers in that thickness.
I was in the middle of answering your original post when I see you added a few other questions in subsequent posts in the thread.
I touched already on the ILD question, and I see you’ve settled on the 30 ILD D30 polyfoam core.
Regarding the 5" thickness, a 5"-6" polyfoam core is commonly used in the mattress industry, but the thickness of a mattress that is either “needed” or “preferred” would depend on the combinations of the layers and components that are needed to achieve the design goal of the mattress and provide the PPP (Pressure relief, Posture and alignment, and Personal preferences) that can best match each person and their unique body type, sleeping positions, and preferences. In the end, you won’t know if the comfort or thickness meets with your needs until you have the completed configuration at home and are able to personally test the completed combination.
As you’re creating your own DIY mattress, you may wish to read option 3 in post #15 here and the posts it links to (and option #1 and #2 as well) so that you have more realistic expectations and that you are comfortable with the learning curve, uncertainty, trial and error, or in some cases the higher costs that may be involved in the DIY process.
The 3 lb density is lower than I recommend for a memory foam topper (4 lb) so realize that in a component system it may have a shorter comfort life and may require replacement sooner, but since you’ve already purchased the topper I would not replace it until it becomes uncomfortable for you. If you do end up replacing it in the future, you may wish to consider a memory foam topper that is 4 lb or above in density.