DIY Mattress Guidance

Background: I’m 5’9" 370 lbs, back sleeper primarily, but will shift to side or stomach when I get too hot. My wife is 5’7" 125 lbs, mostly side or stomach sleeper. With such a difference in size and sleeping position, I’m concerned about finding something that works for both of us.

We are currently on a King Beautyrest Black Hybrid (Clermont model) purchased at Mattress Firm about 5.5 years ago. The store model was incredibly comfortable for 5-10 minutes, but when we got it home it’s been far too soft and sleeps super hot. A Beautyrest rep recently told me that one of the foams they used in that model proved too soft and didn’t hold up, so they’ve discontinued use of that particular foam. I’m sure my size didn’t help either. It’s currently dipping pretty far around the hips and is hell on my back.

Prior to this I had (when single) a Serta interconnected spring with 2" memory foam eurotop I got from Sam’s Club. It was great for about 10 years until I wore it out. But now we’d like something with more motion isolation.

In my previous post, I was looking for advice on picking a replacement mattress from MF, thinking they were going to support a warrantee claim on our current model. That’s not going to happen, so I’ve shifted focus. Last time, a “hidden split” king was suggested, with different firmness lower layers, and a single top layer (since we have young kids we don’t want to get stuck). I hadn’t considered this approach, but like it.

I’ve also done some more research, and realized that it may be possible to salvage the coil unit from our current mattress. Ours is supposed to have Beautyrest’s T3 coils, which were sold as a more durable coil. Being only 5.5 years old, I’m inclined to think that they may still be usable as a base layer in a DIY build. Best I can tell having not cut into my current mattress yet, they should be 8" tall, with another 7.5" of various foam layers above. I like the idea of a hybrid mattress for the cooling/airflow and bit of bounce that the coils may provide. I’ve also considered keeping my current mattress whole and just getting a Leggett and Platt coil unit to build on while we tinker, so we have something that we can sleep on if we hate or need to return layers.

From there, I’m thinking a latex transition layer above the coils. I recently got to test some all Dunlop mattresses, which were pretty good. I like that Dunlop is supposed to be more durable (good for my weight). The place where I tested couldn’t (or wouldn’t) tell me the ILD of the foams used.

On top, I’ve been debating between another latex layer or a memory foam layer. I understand that the top layer will wear out first, and that memory foam will not likely be as durable as latex. One of the pros of a DIY mattress for me is that I can change out layers as they wear out, without needing to drop thousands on a whole new mattress. I understand the Tempurpedic foam is better quality…would one of their mattress toppers make a good top layer (inside the mattress cover)? I’ve read they can feel pretty soft…but are they too soft, particularly for a big person?

Feel/preferences: I’ve generally been most comfortable on something medium-firm…at least in the store. I know it will soften some as it breaks in, and I’m concerned that it will become too soft (like my current mattress). That said, I’ve experienced some that are far too firm. We have a Casper from Costco in our guest room, and out of the box it was far too firm for me…pressure points, pain, and waking up all night. As it broke in, it’s a little better but not great. Likewise, some of the firm mattresses in the store have me feeling more pressure points. I know a firmer foam is more likely to last under my weight, but I am trying to balance that with comfort. My wife would prefer something fairly firm, as she enjoys stomach sleeping. Being considerably lighter, her firm will probably feel softer for me.

So I’m looking for guidance on a build. I’m ok making a few mistakes along the way and spending a little money if it helps me get to what is best for us. As stated, I’m leaning toward a base coil unit. Above that, what thickness/ILD of Dunlop latex would your recommend for each of our sides as a transition layer? I’m likely to go for a GOLS or equivalent all-natural latex as I’ve heard it’s most durable.

For a top comfort layer, I’m open to suggestions. We’ve not experienced Talalay latex, and I’ve read people can have very strong feelings about it. I did try a 2" convoluted Dunlop top layer which wasn’t bad. We currently have many layers of memory foam, and I think I like the feel, though it does sleep hot and I don’t like how much we sink in. I’m worried about making the mattress too soft by putting too much material above the coils. If I went with the 3" Tempurpedic Supreme over a 3" Dunlop latex layer, that would make a 14" overall height which I fear would be nearly as soft as our current 15.5" mattress. I’ve also seen reviews that the Tempurpedic topper is pretty soft…maybe there’s a quality foam that’s a bit firmer for the comfort layer?

What recommendations do you have? Help us, Mattress Undergound! Your’re our only hope!

I’ll comment as a fellow reader - on the top layer part - as I just bought a tempurpedic supreme topper. At the moment it appears that it is only available in a 3 inch, so there is no option to consider a thinner tempurpedic topper. To me, it feels on the firm side for memory foam, similar to the feel of the classic tempurpedic beds in the old days. However I’m light at 140 pounds. For you at a heavier weight you will probably sink pretty far in, and maybe find it softer, but at 3 inches maybe that will be just fine, if your Dunlop transitional layer below it is on the firmer side? Your wife at 125 pounds may find it medium-firm as I do. But maybe it can be just on one side of your DIY?
Good idea to customize things differently for the 2 of you to some degree if you can.
as for heat, The tempurpedic topper does sleep hot, however it comes with a cover on it, and the more material between you and the foam, that can reduce the hotness. If you are putting it “inside” the mattress and under the top fabric layer, that may well keep the heat down sufficiently. I just got mine, but what I’m doing is I have it on top of the bed with its cover on and then also a mattress protector over it, and that keeps the heat down.

if you have a “relax the back” store near you, they carry the Temper Pedic topper so you can give it a try

there is one negative to covering it up with extra mattress protector to block the heat , which is that then you lose the feel of the conforming, “sinking into sand” feel that is classic for tempurpedic. That is a tradeoff

If you do end up doing “surgery” on your old mattress, cutting it open, changing out the foam to new material, and then closing it back up, do report back on the outcome! there are You tube videos of people in your situation doing this and keeping their old mattress’ coils and outer covering.

Unfortunately the closest Relax The Back is a good handful of hours from here. And if I do surgery, I expect I’ll bite the bullet for a new zippered cover to keep everything contained. I’m rotten at sewing. But I can definitely report back! Thanks for the input from both so far!

Due to the rather drastic differneces in BMI between you and your wife I think a DIY mattress with split layers would be a really good idea in this case. I would be hesitsant to destroy your current mattress as I went down that same path early on and ended up not using anything from my old mattress (it wasn’t a Beautyrest Black, that may have slightly better components). Your BMI is going to need a fairly stiff base support layer to ensure you have proper alignment then additional comfort layers as needed. Something to think about anyway.