The base foam is a critical part of your memory foam mattress. No matter how luxurious the memory foam top layer, cutting corners on the base layer will produce an unsupportive and uncomfortable bed.
There are a huge variety of foam base layers you could use. Most manufacturers use polyurethane foam in the base layer, so this discussion is limited to that product. I would be interested to hear from people who have used other foams, especially latex.
Be careful of exceptionally good deals – the foam could be low density, or a cheaper layered construction. We’re looking for one giant chunk of foam. If there is a foam supplier in your area, this is usually your best option.
This was discussed extensively in differences between memory foam, so I’ll keep it short here. Typically, high end memory foam beds will use 2.2 lb/cf polyurethane open-cell foam as the base layer.
Luckily enough, this is one of the most common foams used for basic foam mattresses! So, all we need to do is buy a foam mattress which meets or exceeds these specifications. Look for a minimum of 2.2 lb/cf, and a firmness rating of at least “medium”. This is the major load bearing part of the bed. The memory foam distributes the pressure evenly, but the base layer distributes the load to the bedframe. Without a quality base layer, the mattress will sink and sag – no good!
What I Did
I used a Sultan Fangebo foam mattress from IKEA. This mattress is a solid chunk of 3.5 lb/cf foam, and is found to be medium to firm by most reviewers. There’s just one problem – IKEA appears to have discontinued this model. The newer ones use cheaper foam in layers, which isn’t really what we’re looking for at all.
The good thing is that what we’re looking for is dead simple – a roughly 6″ thick layer of 2.2 lb/ft3 polyurethane foam cut to standard mattress sizes. Check out foam distributors online if you can’t find one in your area.