Building a Mattress: Have a few questions

[phoenix]

Hi androiddd,

I’ve been reading this forum for a long time, but this is my first post.

Welcome to the Mattress Forum! I’m glad you’ve found us and have taken the time to contribute.

I’m in the process of designing and building a new mattress, and also trying to improve a formerly built DIY mattress. We are both back and (sometimes) side sleepers.

I’m not sure if you’ve found it yet, but some of the better comments and links I have for designing a DIY mattress are listed after Option #3 in this post. Even if you were extremely knowledgeable about foams and mattress design, there is quite a bit or trial and error that can go into designing your own mattress, but some people (such as yourself) enjoy “tinkering” and derive satisfaction from your own personal creation.

Here’s my question: although I am sure that buying the softer support foam would hopefully fix the feeling of a hard bottom to the mattress, it means tossing out a perfectly good piece of support foam and spending more money. I’m curious if anyone has any good ideas about an intermediate layer of foam which would sit between the 3" 5-pound memory foam on top and the very firm support foam on the bottom

I wouldn’t be able to tell what material might work best for you, but it does make sense that you are “feeling through” the 3" of memory foam and then the 2" of “soft” (you didn’t mention the ILD) Talalay latex to the firm polyfoam core. I would expect that in this combination you’re going to “feel through” to just about anything placed underneath, as memory foam itself isn’t a very supportive material nor does it show much resilience (rebound). Keeping the firmer polyfoam core and then the upper 3" of memory foam, a more progressive construction using a more “medium” latex (such as the Dunlop you mentioned) or a good density (1.8 lb minimum) polyfoam in the “medium” range could work as a better transition layer, better matching the compressed feel of the memory foam on top instead of being closer to it in feel than the plush Talalay latex was. There’s more detail about typical “progressive” construction you should read in this article. There’s certainly no reason that using the firmer polyfoam support core wouldn’t work for you, but I think that even if you chose the softer polyfoam core that you’d still want to consider a more “medium” transition layer as you described, so logically you may wish to begin with this and then perhaps decide if you wish to change to a different support core.

The main bed build will also source most of the components from the Foam Factory. It would start with a 5 inch layer of medium firm poly support foam, the HD 36 HQ foam with an ILD of 35.

If the “main bed” is also a queen like the guest bed, why wouldn’t you buy this polyfoam core at the same time as the transition foam for the guest bed and then have all of that to play with? Just a thought.

The challenge for this mattress is that it needs to work for a 205 pound 5 foot nine man as well as 115 lb. 5 foot three woman. So it might involve some split layers.

That’s easy enough to do with an electric meat carving knife after the fact, should you desire to customize the transition and uppermost foam layers within the mattress. That’s one of the nice things about an all-foam DIY project.

The transition layer might be 1 or 2 inches of medium firm Dunlop latex, with an ILD Of 29. This should allow the heavier one of us not to bottom out against the support foam. Input as to whether one or 2 inches would be preferable would be great. I’m not sure that 1 inch would be enough of an intermediate layer to stop me from bottoming out.

While I understand what you “mean” by “bottom out”, I want to comment that you won’t be compressing the foam to it’s minimum thickness. All of the foam layers of a mattress work together, not individually or sequentially, so you’re desiring something in the transition layer that matches better with the “compressed ILD” of the uppermost layer so that this transition from the comfort layers to the base foam isn’t so abrupt, if I understand this correctly. You’re correct that only 1" of latex probably won’t have as much impact as at least 2" of the “medium” Dunlop that you are considering in this case, and something like this is certainly a common choice used by many mattress manufacturers.

The top comfort layer could either be a simple 3-inch layer of 5 pound Visco memory foam, or could be two individual 2" layers of 5lb and 4lb Visco memory foam. The advantage I see of splitting the comfort layer into two layers is that they could be swapped from up and down to change the firmness slightly.

I think in these scenarios, if splitting, I would consider splitting the memory foam layer(s) as well as the Dunlop latex “transition” layer. This could give you options for moving the latex up or down in the order of comfort layers, as well as allowing you to place different ILDs of latex on each side.

In the scenario using two different 2" memory foam layers over the latex transition layer, this of course would allow for more comfort “tinkering” by moving the latex layer up within the ordering. But rearranging the two memory foam layers (4 lb and 5 lb) on top of each other in the #1 and #2 positions won’t have as much of a noticeable difference in comfort, especially once your body temperature has impacted the viscous nature of the memory foam after 10-15 minutes. All memory foam is relatively soft (in the low to mid-teens for ILD), and while there are subtle differences in feel, responsiveness to heat, rebound and speed of viscosity change, it would be minor in perception as compared to different ILDs in latex or poly foam.

As I think you’re already aware, I can’t predict what might feel “best” to you, but only comment upon the ideas you’re considering. In the end, as I think you’ve already discovered, only your own personal testing will be able to determine if what you’ve constructed will meet with your personal comfort preferences, so hopefully some of my comments here have bene helpful.

And while I know you’ve been dealing with Foam Factory (aka Foambymail or FBM and other names as well) you may still want to read this post and this post and this topic (about their polyfoam and sources) and this post (presumably from a past employee) if considering anything else from them and some of the information and sources of their foam products.

Phoenix