I recently discovered a couple of moldy spots at the bottom of my memory foam mattress that I had been using for 10+ years. The mattress was on top of a solid base platform bed (i.e., no slats). It appears that other memory foam mattress owners may have the same issue because memory foam doesn’t circulate air as well and tends to get hot. I am now looking to buy a latex mattress but am concerned that we might encounter the same mold issue at some point down the road. Does anyone know whether latex mattresses might get moldy too? Do we need to replace our bed (prefer to not have to do this) or get a slatted foundation to put between the latex mattress and the solid base platform to make sure this doesn’t happen again? Thanks in advance for any feedback.
Hi myconfidant,
Welcome to the Mattress Forum! 
Your questions about mold, breathability, foundations and mattress materials is a good one, and it comes up every so often here on the forum. This allows me the opportunity to speak to this again – thanks!
Environmental conditions and degrees of humidity can play a role with potential mold formation under any mattress. The degree of moisture in the wood decking of a platform bed base itself would also be one of the variables. The fabric that was used in the mattress ticking and the quilting could also increase or decrease the likelihood of moisture retention and mold. A bedroom in a basement would be more likely to have issues than one on the third floor. A mattress on a floor would also be at greater risk than one that was higher up in the air which was warmer and could come to room temperature more quickly, even in the same room. The degree of moisture that each person releases over the course of the night would play a role. There are many more factors that could be involved but there is usually a combination of factors that leads to mold or mildew formation. Mold and mildew is also not the only issue involved because the airflow through a mattress can also affect the dust mite population (which depends on humidity in their surroundings to absorb the moisture that they need to survive) and can also affect the durability of a mattress (higher humidity can reduce the useful life of many mattress materials).
A solid surface platform vs a slatted base foundation can also have an impact. It’s true that latex does breathe more than other foams and that natural latex also has an inherent resistance to mold and mildew and would have less likelihood of developing mold and mildew for these reasons. It’s also true though that the development of mold and mildew would depend on a combination of several factors coming together. One of the most important of these is moisture (from the environment or the person on the mattress), one is the types of mold or mildew spores that are in the environment, and one is a food source (cellulose is one of these). For example, the temperature difference between a mattress and a solid surface foundation can play a role in condensation which would increase the odds that mold or mildew could develop. A cover or better yet an insulated cover on a foundation could help with this temperature differential vs just having a mattress on wood.
I personally believe that a slatted foundation moves the “risk” of mold formation towards the safer side of the spectrum and if the slats are strong and firm enough and close enough together there is no real down side to using them. This doesn’t mean that a sheet of plywood will be a problem in most circumstances - only that the odds that it could are increased - both because the plywood can absorb moisture over time and because it reduces the ability for moisture to evaporate compared to slats. It would be a bigger problem with less breathable materials like many synthetic fabrics or less breathable foams and natural latex is also inherently “resistant” to mold to some degree but they all have a cover and IMO the risk is still there with latex as well although to a reduced degree.
There are also other considerations that may be important to some people as well such as the glue that is used in plywood (off-gassing) and the benefits of greater breathability in terms of small improvements in sleeping microclimate. The bottom of a mattress is a significant part of its surface area and when you move and “push” air through the mattress, reducing the ability of the bottom of the mattress to allow airflow can reduce to some degree the breathability of the entire mattress although this is not usually a major issue. Innersprings for example are in general more “breathable” than foam mattresses for this very reason because they allow more airflow than any foam even though they are deeper inside the mattress.
For those that have a solid surface support system under their mattress (such as your situation), then something like a this bed rug in between the mattress and the foundation or one of the slat conversions here (which has no flex at all) or even one of the Ikea slatted bed bases here (which has some flex which may change how the mattress feels and performs) could work well and would also increase ventilation under their mattress. I would lean toward something along these lines if you don’t wish to replace your current platform bed base.
Phoenix