Firm Foam Mattress

Thank you so much for this website. I’ve learned a lot by reading questions and answers on the forum.

My husband and I live on a boat and need a new foam sleeping surface. We would prefer it to be firm. We have been using Thermarest self-inflating air mattresses on top of our foam boat cushions, and find them very comfortable, but rather inelegant. My husband it 6’ and 160#, and I am 5’4" and 125#.

We’d like to create a firm surface by replacing our foam cushions and the Thermarest air mattresses, and I’ve been leaning toward a Lux HQ 5" foam from FBM. Do you think this might be a good choice to replace our current arrangement?

As we live on a sailboat, we’ll need to cut down the foam at one end and bevel it a bit to fit the aft cabin. I had been attracted to the idea of Dunlop latex as the sleeping surface as it would give a lot of support, but I cannot find a source for a king-sized piece of the foam, either online or in town (Brunswick, GA). If we bought a “mattress” rather than a sheet of foam, could we cut it down as I’ve described?

I hope that I’ve stated my questions clearly. I’d be happy to hear comments and suggestions.

Hi mainestreet,

I have to say I’m somewhat envious. I’ve toyed with the thought of living on a boat from time to time … and it’s something that is on my bucket list … maybe in retirement (if that ever happens!) :slight_smile:

I would tend towards a more reliable supplier… particularly for an “application critical” project like a boat mattress. You can see some of my thoughts about why in post #2 here and post #2 here and a search on FBM will bring up more comments (if you need them). There are some more reliable polyfoam sources in post #4 here if a local foam supplier that sells polyfoam at a reasonable cost isn’t available to you. Some of these may only ship thinner layers that can be shipped UPS so check for different prices and shipping policies. Some of these have some very good polyfoam information on their sites.

There are some manufacturers that specialize in making mattresses for boats and the variance in shapes and thicknesses that may be necessary. In some cases (as I’m sure you know) they can lead to some very “non standard” mattress sizes and shapes. I’ll include a list of some of them here so you can call them and “pick their brains” about what may be more suitable for marine application because of the humid environment because this is a fairly specialized application. All of these are not local or even close to you but you may be interested in looking at the different websites and ideas about marine mattresses. They include … Holly Hill, FL (A recommended member of this site) Online (A recommended member of this site) (A recommended member of this site) surrey, BC Canada Ft Lauderdale, FL Ft Lauderdale, FL or Ft Lauderdale, FL and Costa Mesa, CA or or Houston, San Leon TX or Portland, ME Plantation, FL West Palm Beach, FL Seattle, WA Saginaw, MI (authorized custom re-sizer for Tempurpedic)

There are many more but this will give you a representative sample and give you a few people to talk with to gather ideas and on the advantages and disadvantages of different materials.

In terms of “regular” outlets … there are not so many great choices in the Brunswick, GA (or Jacksonville, FL) area. Some of the better choices in Jacksonville are in post #7 here but these would be “regular size” mattresses. If you need more options or some choices that are more local … I’ll take a look a little later tonight and see if there is anything right in the Brunswick area. Given the specialized nature of the mattress you need and the environment it will be exposed to though … I would probably suggest taking the trip to Holly Hill and visiting Fox mattress since they are the closest manufacturer I know of that specializes in marine mattresses and I also know them well and think very highly of them.


Hi, Phoenix,
Thanks for your quick and thorough response. I’ve read the links re: FBM, and the other links you’ve provided.

Because we plan to cut the foam ourselves, we won’t need a marine supplier, and usually anything labelled “marine” is priced way above the norm, in our experience. We’ve been living aboard and sailing the world for over 10 years, so we’re pretty confident that we could be successful with a DIY mattress project now that we’re back in the US and can get good quality products and reliable shipping. It’s really no different being on a boat than being in a cottage or in a house, in that it doesn’t require any special mattress considerations, though the industry might believe that it does. I would add that we don’t want or need a high mattress, that 5- 6" in all would do for us.

I’ve decided against latex now, as people have remarked on how heavy it is, and we need to move the mattress occasionally to get into the lockers under the bed. Maybe my idea is too simple, but I think we’d be comfortable on a
firm piece of foam, maybe ILD 50 if I can find it, with a mattress pad on top. We don’t want the sinking-in feeling.

What I think I need is one piece of foam that is Eastern King Size that I can cut minimally to fit our aft cabin. I don’t want multiple pieces. I’ve found some good resources on your site and I’ll continue to peruse them for price differences.

My question is, you if you don’t mind, would the 50 ILD be adequate firmness for two people our sizes (6’ tall, 155# and 5’4", 125#)?
Many thanks.

Hi mainestreet,

I agree with you that anything that has a specialty use in it’s advertising (whether it is “marine” or “organic” or other specialty terms) will often be more expensive than the same thing without the label although this is not always the case with mattress manufacturers who also make “regular” mattresses.

I would also be one who believes that marine environments would require foams and materials that are more resistant to higher humidity levels and more resistant to mold and mildew and corrosion. While I have no direct experience (that’s waiting for a few more years :)) the salt air and humidity “should” have an effect on mattress materials and mold and mildew depending on the foam used, any metal in the mattress, and in the quilting and ticking fabrics as well.

You’re right that latex is very heavy … particularly Dunlop latex. Higher density/quality memory foam is also very heavy (similar to latex) but is only used in thinner surface layers not the support layers.

I did take a quick look around Brunswick and I didn’t see any polyurethane suppliers there or any outlets that may carry what you are looking for … I did see one in Jacksonville that sells polyfoam in mattress sizes that may be worth a call.

50 ILD is really firm and may be too firm, especially for your weights, and for most people would be unsleepable. You would probably need a softer top layer that was thick enough over this to isolate you from the firmness of the base and this would depend on your body types (besides just height/weight), sensitivity to pressure issues, and sleeping positions. The relationship between foam firmness (IFD or the older term ILD) and compression modulus (the rate that a foam gets firmer also called sag factor, or comfort factor) is also a very important part of the “comfort” and support qualities of a foam and plays at least as big a role in how a foam performs as the ILD/IFD. Higher quality and density foams tend to have a higher compression modulus and higher density foams are also more durable as well (and also more expensive).

While foam is fairly easy to cut with an electric knife, at least to size and shape, bevelling is more dificult. An issue that may also come up with cutting or especially beveling the foam yourself is that a standard mattress cover won’t fit and you would need to do some custom sewing to finish the mattress and hold it together.


Hi, Phoenix,
Thank, for the extra comments and answer to my question. I’ve spent the day looking at every website you recommended and the list of foam websites, as well.:blink: My top choice right now is foamonline’s HR firm (44), 3#, cut to order for $532.10. I like that I can order it online, and that they have free shipping. I’ll call and talk to them before I order.

I’ll keep you posted, as things develop.