Does Plywood Under The Mattress Help?

Mattresses are known to develop sags, also known or referred to as “soft spots” after some years of use. This also happens after a few months of using a new mattress if the quality of the mattress is poor.

Where the problem with a mattress is lack of support due to sagging, using plywood helps. All you need is to purchase plywood of your preferred thickness and place it on your bed base or on the slats of your bed frame.

Screw the plywood sheet to the bed frame. Once done, simply place your mattress on top of it.

Ideal plywood sheets to place under the bed

Use plywood sheet that is at least 19mm thick when putting together your bed frame. This will ensure that your mattress receives ample support from below, keeping it from sagging. It is a temporal or short-term fix for anyone who is not in a financial position to purchase a new mattress.


One way of identifying a sagging mattress is sinking whenever you roll or move over to the centre of the mattress. Plywood becomes the ideal but temporal fix as you prepare to purchase a new mattress.


A mattress can sag for either one or two reasons, namely; the destruction of a beds’ base, especially in the case where bed slats break due to excess weight of the bed user, and in particular where the slats are weak, leading to insufficient support. Another reason is the breakdown or wear of the internal support mechanism of the mattress.

Old mattress and plywood pieces

Old mattresses are known to sag. Where this is the case, you can opt to use pieces of plywood or cut a piece that matches the shape and size of the sagging portion of the mattress. Place the plywood piece right under the mattress and directly to the sagging part. Doing this will keep away the dent in that part of the mattress.

Setbacks of using plywood under the mattress

Whenever plywood is used to support a mattress, less air if any circulates under the bed because the mattress lies flat on the plywood sheet. This results in growth of mildew, a common occurrence for people living in humid regions and wet climatic conditions.

The mildew destroys the mattress, making it undesirably soft and unhealthy for use. It becomes a breeding ground for all manner of microbes such as yeast and bacteria.

Use plywood for a short period of time

Another setback in using plywood is that it also causes a mattress to wear out faster when the wood splinters, causing damage to the mattress fabric. Use of plywood for long is therefore discouraged.

Consider the possibility of acquiring a new mattress or box spring before use of plywood becomes a non-viable solution for you.


You can lengthen the time of service your plywood sheet and sagging mattress gives you by occasionally taking them outdoors for aeration. This is especially helpful when done under direct sunlight. It aids in killing any microbes that may have started forming under the mattress.

Does putting plywood under a mattress make it firmer?

The answer to this question is yes. Putting plywood under a sagging mattress gives it a firm base. The plywood is made of several layers of wood which are glued together to make a bed sufficiently firm.

Use of plywood is cost-efficient and an easy way to add firmness to a sagging mattress. A firm mattress guarantees adequate support to the body and a good night’s rest.

Best plywood thickness to place under the mattress

The thickness of the plywood sheet used has an effect on the firmness of a bed. The type of mattress you have is what will determine the thickness of the plywood sheet you will purchase.

Ideally, plywood sheet that is used for a bed should not be less than ¾ inch in thickness because it tends to be weak, making it unable to support the weight of the mattress as well as the weight of the bed user.

Always consider the weight of the mattress and that of the user in determining the thickness of the plywood to settle for.

Mattresses warranty

The warranty of a mattress can be made void by use of plywood. Always look keenly at the warranty card for terms and conditions of the warranty before using plywood under your mattress.

Usually, the warranty card is clear that changing or modifying the original design of the bed or bed base will void the warranty given by the manufacturer of the mattress.


Moisture in the mattress is both a health hazard to the user and to the mattress itself. Studies have shown that 25% of the moisture emitted by the human body during sleep is usually absorbed by the mattress.

The moisture results in mold below the bed and a thriving of dust mites where the environment is not only humid but also warm. Mold and mildew release allergens into the air, causing respiratory health problems.

Advantage of having plywood under your mattress

One of the main reasons for using plywood is that your bed may not be firm enough at the time of purchase. This demands reinforcement, bringing in the need for plywood.

Another reason for use of plywood is that the mattress user may have a back injury or even back pain, body aches and body discomforts caused by a sagging mattress. A doctor is likely to recommend a firm sleeping surface for you, thus necessitating the use of plywood.

Increase in number of bed users

Use of plywood board or sheet is also necessary when the bed users increase, as in the case of a married couple or when there are visiting guests without a guestroom to host them. The increase in number of users results in increase of the amount of weight the mattress and the bed frame in general need to support.


Placing plywood sheet on top of a box spring or bed frame provides additional layer of support to your mattress, helping to make and keep it firmer for a longer period of time.