Foam Series: Layering Foam for Mattresses & Cushions

SKU: X-HT-300495



If your next DIY project involves foam, such as a boat cabin mattress, patio cushions or a new sofa, you have some options when it comes to the feel of your application. Depending on your comfort preference, you can customize how your cushion or mattress feels by layering different types of foam on top of each other. Let’s get into it!

Before we begin, you’ll want to make sure you have an understanding of foam terminology — specifically, the terms "density" and "indentation force deflection" (IFD) and how they relate to your project. Check out our blog “Foam Series: 5 Important Foam Terms to Know” (#300052XHT) to get acquainted with these. You’ll also want to make sure you know the CushionRite® foam products offered at Sailrite. It’s a good idea to read our “Foam Series: Comparing Types of Cushion Foam” (#300053XHT) blog for more information on what type of foam is best for you.

When it comes to layering foam, you have some wiggle room to experiment. The layering process is subjective depending on how you want your foam to feel and what the foam will be used for. To make foam selection easier, we recommend you first get your hands on our Foam Sample Box (#124215). It includes samples of every type of CushionRite® foam we stock and explains their recommended uses in an easy-to-understand insert. It’s truly the best way to practice layering foam pieces firsthand and see what might work best for your project.

The concept of layering foam can be used to achieve a different foam thickness and/or firmness. Thickness is pretty self-explanatory, but firmness is how the foam feels to you. To adjust the firmness, you’ll want to use a firmer foam with a higher IFD as a base and layer a softer foam with a lower IFD on top. This method works for cushions and mattresses. Think of the firmer base layer of your foam as a stabilizer, kind of like the box spring on a mattress. It gives you support even if the softer top layer of foam starts to bottom out over time. This will ensure that your cushion or mattress still feels comfortable, even with everyday use.

In the foam layering recommendations below, you’ll notice that every combination uses Moisture Prevention Underliner (#121766) as the bottom layer. This material does not go inside your mattress cushion cover. It is a high-strength mesh material designed to promote consistent airflow underneath your mattress, minimizing condensation, mold and mildew growth. It rests between the bottom of your cushion and the platform below.

The Common Approach

If you’re looking for a simple formula for boat mattress layering, take a look at the graphic below. With only three layers, it creates a thinner mattress. It’s also a more cost-efficient layering combination. If you do not frequently sleep on your boat, or you don’t have a lot of headroom, this might be the best approach for you. You’ll notice that the top layer of this common layering approach is either CushionRite Premium (a high density polyurethane foam) or CushionRite Dry Fast (an open cell foam). Keep reading to understand the difference between these two foam types and how to know which one is right for you.

Polyurethane vs. Open Cell Foam

You’ll notice that in all of our foam layering formulas, we never layer CushionRite Premium and CushionRite Dry Fast together. Both foams have their benefits, but they are unique. So decide for yourself what is more important to you — a foam that dries out quickly (choose Dry Fast) or a longer-lasting, more comfortable foam (choose Premium). If your boat cabin gets very wet, we recommend you go with Dry Fast. If you are a liveaboard, you will get much more mileage out of Premium.

If you have more space — or just prefer a thicker, more comfortable mattress and are willing to sacrifice some headroom — we have layering recommendations below from Matt and Eric Grant, sons of Sailrite founder Jim Grant. Matt and Eric have lots of experience outfitting their boats with custom mattresses and cushions. Take a look below at their recommendations to see if these foam layering formulas appeal to you.

Matt’s Recommendations

Your mattress should be at least two to three layers of foam. This does not count the very base of your mattress assembly, which should be our Moisture Prevention Underliner. Boat mattresses differ from the ones in your home due to space concerns. Most boats, even large yachts, don’t have a lot of overhead room in the sleeping berth, so you do not want your mattress to be too thick. Otherwise, you’ll be encroaching on valuable sleeping space. You’ll want to be mindful of your cabin dimensions when you choose your foam.

This first layering example uses two firmnesses of CushionRite Premium, our high density polyurethane foam. This foam combination favors long-lasting support and comfort over breathability and airflow.

If you want a quick-drying mattress that has excellent air circulation, go with two layers of Dry Fast in varying firmness ratings on top of the Flotation foam and the Moisture Prevention Underliner layer. This is my recommendation for wet sleeping berths. Dry Fast is not as comfortable as Premium, so that is why I recommend at least 2 inches of the soft firmness rating of Dry Fast as the top layer.

Eric’s Recommendations

Your mattress should be at least two to three layers of foam and should have at least 3 inches of CushionRite Premium (Firm) foam in it. In fact, the more often you intend to sleep on your mattress, the more you’ll want to use a thicker, firmer piece of foam. So if you’re a liveaboard boater, you’ll absolutely want a high density (CushionRite Premium) foam. This will help combat any bottoming out that occurs, especially if you’re going to be putting a lot of weight on the mattress. Putting CushionRite® Dry Fast foam as the topmost layer isn’t going to be the most comfortable, and you should avoid it unless you’re really concerned about excess moisture and sweating. It's recommended that you make your mattress at least 4 inches thick, if not thicker.

For a very thick mattress (if space allows), you may want to use two 4-inch sheets of firm Premium foam and just one 2-inch sheet of Premium foam of soft or medium firmness. Another option would be to have one 6-inch layer of firm Premium foam and a 4-inch layer of softer Premium foam. Both of these would need the Moisture Prevention Underliner beneath them. If you're really concerned about moisture, you can also add a layer of Flotation foam with small holes drilled in it (this is useful in any foam layering combination). The Flotation foam always goes underneath your Premium foam, like in the image below.

Wrapping It Up

As you’ve probably gathered by now, the possibilities are endless when it comes to layering foam. It’s truly up to you! Even our experts agree that there’s a lot of wiggle room as long as you understand what each foam is capable of. If you still have questions, comments or concerns about your foam project, feel free to reach out. Our knowledgeable support staff is available through email, phone or the chat function on our website. You can also comment below and one of our crew will get back to you. We’re always ready to share our DIY tips and tricks with you.

Footnote: This blog was updated in March 2023 for new foam layering recommendations and updated foam offerings.