How To Fix A Sagging Mattress With Plywood

Plywood is excellent for fixing a sagging mattress whenever the option of buying a new mattress is not viable because it is easily affordable.

All that is needed is good quality plywood sheet to give added firmness and support to the mattress and the user during sleep.

Plywood helps to reinforce a bed base for maximum support whenever a mattress has a noticeable sag or appears to need support in specific areas.

Health challenges that come with sagging mattress

A sagging mattress is one of the major causes of backaches, spinal pain, hip pain and stiffness. When this is the case, you will notice that you wake up with these pains, but as the day progresses, they begin to wear out.

How to inspect a sagging mattress

Check the area of the bed base that needs to be fixed. Look for dips or sagging spots in the middle of the mattress in order to determine the parts of your bed frame to reinforce with plywood.

Lie on different parts of the mattress and compare the firmness of all the parts. You may notice that the springs of a box spring mattress can be felt through the mattress because they are poking through.

Use your hands to feel all the parts of your mattress for dents, or for hard and lumpy areas. Where you detect a sag, place a ruler or straight rod on the place and you will be able to see the dent.

How to use a yardstick to check a sagging mattress

Another way of checking if your mattress has sagging areas is to use a yardstick. Place it across the top surface of your bed.

You will notice gaps underneath where the mattress is sagging. Pay special attention to the areas where the heavy parts of the body tend to lie when you go to bed, such as the shoulders and hips.

Check the head area as well, particularly if you are the kind of person who does not like to use pillows for head support.

How to fix your bed base and a sagging mattress

Measure your bed base in order to purchase a plywood sheet that fits its dimensions. You may realize you need plywood to fit the size of your entire bed frame, or you only need well cut pieces of plywood to only cover the affected sections.

If you cannot get a ready-made plywood of the right size, buy a bigger one then cut it to size. Place your plywood sheet on the bed base, then place back the mattress and test it for comfort.

The sag should have reduced or been largely eliminated. Fixing plywood is easy. You do not need help unless the plywood sheet is too heavy for you.

Bed bases and plywood

Plywood can be placed on most bed bases such as those bed bases made of slats or box spring. The plywood used should be strong enough. However, you cannot use plywood on an inner spring bed, waterbed or airbed.

Good quality plywood is straight and odorless, or has a fresh woody scent. It also has a smooth surface and smooth edges. It is also clean. Always avoid dirty plywood.

Pick the right plywood for maximum mattress support

High grade plywood and even medium grade are very good for giving great support to plywood bed-frames because they tend to be durable, strong and resilient in accommodating changes in temperatures caused by changing weather patterns.

The density of plywood sheet is what determines its level of strength, and this density is determined by the number of veneers or plies that make up one sheet of plywood. The more the plies, the thicker and stronger the sheet.

Number of people

Consider factors such as number of people using the bed to determine the thickness of plywood sheet to settle for. More people means there is more bed-weight to handle. This may demand that you increase the thickness of your plywood if it wasn’t already thick enough.

Mattress and plywood should be compatible

The right plywood for mattress is also one that is compatible with your mattress. If it is not compatible, you will not get the kind of firm support you are looking for. Where there is compatibility, the life of your mattress will be prolonged.

Also note that some mattress designs may not work well with plywood because plywood hampers the breath-ability of some mattresses, causing a locking-in of moisture inside the mattress, which results in mold and mildew formation. The plywood can also accelerate the rate of wear of your mattress. 

Best plywood for under mattress

Birch is the best plywood to use for under mattress. Use birch plywood core when making your bed frame and bed base. It is a hardwood known to be sturdy and durable.

It is also heavy by nature, is shock-resistant, meaning that it can stand against forces of nature such as very strong winds and thunderstorms, and has good crushing strength. Besides being durable, it is also very resistant to damage.

Texture and finish

Birch wood is fine-grained and has a uniform texture which makes it easier to work with than other hardwood species. It also sands, stains and finishes extremely well after processing, producing very attractive finished products. These qualities ensure that you get the best lumber for your ply. Walnut plywood is also good but it is pricey.

How thick should plywood be to support a mattress?

The right plywood for your mattress is also one that is thick. The thicker the better. Usually, the thickness should be 19 mm for a single bed, going all the way to 40 mm for double beds.

Where possible, test your mattress and the plywood for comfort before purchasing the plywood sheet. This is important because every person has a different experience when it comes to comfort on a bed. This makes it difficult to determine the kind of plywood thickness that is perfect for everyone.


Although plywood solves the problem of a sagging mattress, the mattress will continue to sag over time and eventually you will need to purchase a new mattress.