Wood Foundation vs 'Semi-Flex' Foundation for Latex Mattress


Do you think a typical wooden foundation made for latex/foam mattresses would offer significantly more stability than the Leggett & Platt “Semi-Flex” foundation? We’re currently on a new SleepEZ 13,000 Cal King on top of a 1-year-old Beautyrest Black “Triton” foundation - I’m pretty sure it’s the L&P “Semi-Flex” foundation - I’ve seen interior pictures of both, and they look identical. We have our foundation on top of a cheap (free with the last mattress), but seemingly sturdy metal bed frame. After reading some of the previous posts, and your replies, I think we could achieve better motion isolation if we were to switch to a wooden foundation. Do you think that is the case? If we did, I would also get a new “super heavy duty” wedge-lock metal bed frame, just to cover all my bases.

I’ve found quite a few decent-looking assemble-yourself foundations in the $200-300 range for a Cal King through links from your site, googling, and searching eBay . We can also order the much nicer OMI foundation through a local dealer, and they’re on sale for 3 more days for 20% off with free delivery AND (that corny) ‘white glove’ installation for like $640. I feel it’s worth it to me to spend more for a presumably higher-quality product, also considering they will get it installed under that monster of a mattress. I think it’s a few extra hundred bucks well spent, especially since I don’t really have anyone to help me change out the foundation & frame, and I will probably kill my back otherwise.

That being said, am I wasting my time and money trying to improve on the existing semi-flex foundation? Shawn said we should use it and it would be just fine, but I’m not very happy with the motion isolation we have so far. He said it would get better as the top of the mattress cover “stretches out”. I would agree that is the case, it HAS gotten better, but I don’t think there is much stretching left, and I still feel a great deal of movement in the mattress, i.e. I can feel the mattress shake when my wife rubs her nose…however, I have not been woken up in the middle of the night by my wife getting in and out of bed, which may be more of a testament to my ability to achieve a deep sleep, rather than any comment on the mattress.

Phoenix, I would certainly welcome your expert opinion, especially if you could find out how much these two types of foundations “flex”.

Any contributions from other members are more than welcome.

Thank you!
LA Sleeper

Hi LAsleeper,

This is an interesting question and actually has several interrelated parts as it regards motion transfer.

The Triton foundation is a strong and solid foundation with very limited flex which is as you say very similar if not identical to the L&P semi flex.

Because the flex with this is very limited and with 12" of latex over it I don’t think that you will see any noticeable difference with a foundation that is “no flex”.

Motion transfer though really has two parts to it. Latex is very “point elastic” and because of this larger motions only affect a smaller area around the point of compression than other materials. In a way … it’s the pocket coil of the resilient foam world because each “area” can flex more independently without affecting the area around it. Other than memory foam … latex is the most point elastic foam material and in this way is similar to memory foam although it has a “valley shaped” impression more than a more “canyon” shaped impression (steeper walls around the impression which means less of the surrounding area is affected). On the other hand … latex is very resilient which means it returns about 70 - 80 % of the energy that is applied to it instead of absorbing most of the energy in the material like memory foam (the mechanical energy is transformed into heat). This means that smaller movements can travel through the material instead of being absorbed. Memory foam will absorb these smaller movements. I believe this is what you are feeling. In other words it transmits more of the smaller movements than memory foam.

Some people are more sensitive to this than others and talalay in softer versions (which is desirable for it’s pressure relieving qualities) is more susceptible to this than firmer foam or Dunlop (which has a denser cell structure). I believe this is because it will react more to smaller movements than firmer foam and this can travel through the material. This is part of the characteristics of a rubber material. This can also be aggravated by having a cover which is tighter at the beginning and will lessen when the cover goes through it’s initial stretching and transfer less movement but will not stop the “vibration” transfer which is a function of the material and it’s firmness and how this interacts with the people on it.

The solution to this would generally be to use a layer on top which can help to absorb these smaller movements. This could range from a wool puddle pad used as a protector to a thicker stretch cotton, synthetic fiber, or wool mattress pad or even a thin layer of memory foam (say an inch) which will all to differing degrees absorb the smaller “vibrations” that travel through the material and isolate them from the people on the mattress.

Which of these may be best can depend on the degree of sensitivity of the people and the amount of transfer that is happening on (or in) their mattress.

I hope this helps and fits the “symptoms” you are experiencing … and again … I doubt that a firmer “no flex” base will make a significant difference to this type of motion transfer and I (like Shawn) think that the Triton is just fine.