A too-soft mattress creates an unsupported sleeping surface that causes back pain, disrupts sleep quality, and makes getting in and out of bed difficult. You can make a soft mattress firmer by adding a firm mattress topper, placing a plywood board between your mattress and foundation, or adjusting your bed's support system.
This comprehensive guide provides 16 effective tips to make a mattress harder, including modifying your existing mattress, adjusting your bed's foundation, and environmental changes that affect mattress firmness.
Whether your mattress has gradually softened over time or was too soft from the beginning, these practical methods help transform your sleep surface without necessarily purchasing a new mattress.
Implementing the right firmness-enhancing technique can significantly improve spinal alignment, reduce back pain, and enhance your overall sleep quality.
Contents
Purchase a firm mattress topper made of dense latex, high-density memory foam, or compressed wool to instantly increase the firmness of your sleep surface. Look for toppers labeled as "firm" or "extra firm" with a thickness of 2-3 inches (5-7.6 cm) for optimal support.
Natural latex toppers provide the most significant improvement in firmness and offer excellent durability. Simply unbox the topper, allow it to expand if needed, place it directly on your mattress, and secure it with your fitted sheet.
This solution works immediately and requires no special tools or expertise. The drawback is the upfront cost, which ranges from $50 - $300 depending on the size, material, and quality, but a quality organic mattress topper lasts 3-5 years and provides consistent support.
Insert a 3/4-inch (1.9 cm) plywood board between your mattress and box spring or bed frame to stiffen up your bed foundation. Cut the plywood slightly smaller than your mattress dimensions for easier handling. Sand all edges to prevent splinters and damage to your mattress.
The wood prevents the mattress from sinking into the box spring or slats, which creates a completely rigid base. Plywood costs under $50, makes your mattress feel firmer immediately, and provides significant improvement, especially for innerspring mattresses.
If you use a board, perforate it and cover it with fabric to help ventilation, because body heat is normally dissipated through the mattress, and it could become trapped without ventilation.
Use untreated plywood to avoid chemical exposure. I recommend you do not use MDF because it contains formaldehyde.
Replace your soft mattress with a firm eco-friendly model if other solutions don't provide sufficient improvement. Look for mattresses labeled as "firm" or "extra firm" made with natural latex.
Research eco-friendly mattress brands such as PlushBeds, Avocado and Naturepedic, that use non-toxic materials certified by organizations like GOLS (Global Organic Latex Standard) or GOTS (Global Organic Textile Standard).
A new mattress provides a permanent fix with the exact firmness level you need. The upfront cost ranges from $689 - $5048, but a quality eco-friendly mattress lasts up to 30 years and eliminates the need for temporary solutions.
If you buy a new mattress, ensure your old mattress is properly recycled and doesn't end up in a landfill.
Review your mattress warranty to determine if premature softening is covered under the manufacturer's guarantee. Many quality mattresses have 15-year to lifetime warranties and in some cases, terms specifically address excessive softening or body impressions deeper than 1-1.5 inches (2.5-3.8 cm).
Measure any depressions by placing a straight edge across the mattress and measuring the gap. Document the issue with photos and contact the manufacturer with your proof of purchase.
If your mattress is new, you may still be within your sleep trial period. That means you can return your mattress for free and choose another firmer mattress instead.
This solution potentially provides a free replacement or repair if your mattress qualifies. Be aware that warranties typically only cover manufacturing defects, not normal wear, and many have prorated terms that reduce coverage over time.
Turn your mattress 180 degrees every 3 months to prevent body impressions from forming in the same areas. I recommend marking your mattress with seasonal indicators (like "Spring," "Summer") to track rotation schedules.
This redistributes wear patterns and prevents the mattress from developing permanent soft spots where you regularly sleep. Rotation works particularly well for new mattresses before significant softening occurs.
The effectiveness increases when combined with other methods like toppers or proper foundation support. Rotation costs nothing and helps extend mattress lifespan, but offers only moderate firmness improvement for already-soft mattresses and requires moving a heavy mattress regularly.
Turn your double-sided mattress over completely to utilize the less-worn side and restore firmness.
Check your mattress tag or manufacturer's website first, as many modern mattresses are one-sided and not designed for flipping. If you want to make a memory foam or pillow top mattress firmer, you would need to use one of the other tips such as a mattress topper.
For flippable mattresses, this technique provides an immediate firmness improvement by utilizing the less compressed side. The unused surface will feel significantly firmer if the mattress hasn't been flipped regularly before.
Aim to flip every 6 months, combining with rotation for even wear.
Replace your existing bed base with a platform bed or solid foundation to eliminate the give and flexibility that can make it feel too soft. Platform beds provide rigid, even support across the entire mattress surface.
Look for platforms with slats no more than 3 inches (7.6 cm) apart or with a solid surface. If purchasing a new bed frame isn't feasible, reinforce your existing foundation by adding additional slats or support bars.
Replacing your foundation addresses the underlying support system rather than just the mattress, making it highly effective for many mattress types. The drawback is the higher cost ($200 - $500) and effort required for replacing your bed foundation, but the improvement in firmness is substantial and long-lasting.
If your mattress requires a box spring, replace it if your current one is more than 7 years old or shows signs of sagging. Worn box springs lose tension and begin to sag, directly affecting how firm your mattress feels.
Look for box springs with rigid construction and more internal supports rather than widely spaced coils. When purchasing, choose the correct height to maintain your desired bed height.
For maximum firmness, consider a low-profile box spring with less give. Replacing box springs costs $100 - 300. It provides significant improvement but only works with older mattresses that require box springs.
Reduce your bedroom temperature to 65 - 68°F (18 - 20°C) to make a memory foam mattress firmer. Foam materials become more rigid in cooler environments and softer in warmer conditions, but this doesn't work on other types such as innerspring.
I recommend using a programmable thermostat to lower temperatures at night, or opening windows during cooler months.
The firmness change is immediately noticeable when entering a cool bedroom and costs nothing except potential heating/cooling adjustments. The drawback is that the effect is temporary - the mattress will soften again in warmer conditions - and some people find sleeping in cooler temperatures uncomfortable despite the improved support.
Place your mattress directly on the floor to eliminate any give from bed frames or foundations. First, clean the floor area thoroughly and consider placing a thin moisture barrier like a plastic sheet underneath to prevent dampness.
This creates the firmest possible foundation with zero flexibility. Putting your mattress on the floor works instantly and costs nothing, but it is likely to invalidate the warranty on some mattresses which are not designed to be used on the floor.
Other disadvantages include reduced airflow, increasing the risk of mold, difficulty getting in and out of bed, and potential exposure to dust and allergens from floor level. This approach works best as a short-term solution or for young adults without mobility issues.
Remove all bedding and allow your mattress to breathe for 4-6 hours in a well-ventilated room every 3 months. If weather permits, place the mattress in direct sunlight, which helps eliminate moisture that makes foam materials softer over time.
Moisture from perspiration and humidity gradually accumulates in mattresses, reducing their firmness. Regular airing helps evaporate this moisture, restoring some rigidity to the materials.
This free maintenance technique provides modest firmness improvement and improves mattress hygiene. The limitation is that improvement is gradual rather than immediate, and severely compressed materials won't fully recover through airing alone.
Apply mattress support systems such as Mattress Helper, or use repair tape to reinforce specific sagging areas.
Install these supports directly under the sagging areas between the mattress and foundation. This solution costs $20 - $100 depending on the product and addresses localized softness effectively. It's particularly helpful for mattresses with specific compressed areas rather than a softer mattress overall.
The drawback is that these products create uneven support if not properly positioned, and they don't fully restore severely sagged mattresses but rather provide better support within the damaged areas.
Replace widely spaced bed slats with more closely positioned ones or add extra slats to your existing frame. The ideal spacing between slats is no more than 3 inches (7.6 cm) for optimal mattress support.
Use hardwood rather than softwood for greater durability and less flex. Additional slats prevent the mattress from sinking between supports, creating a more consistent firm surface.
This solution costs $20 - $60 for extra slats and provides substantial firmness improvement for mattresses used on slatted foundations. The main limitation is that installation requires basic DIY skills, and the improvement varies based on your original slat configuration.
Place a bunkie board - a thin, solid foundation typically 1-3 inches (2.5-7.6 cm) thick - between your mattress and current foundation. These boards are available in all standard mattress sizes and create an immediate firm surface.
Unlike plywood, bunkie boards are designed specifically for mattress support, with proper ventilation and finished edges. This solution costs $50 - $150 but provides significant firmness improvement, particularly for mattresses on older box springs or widely spaced slats.
The improvement in firmness is substantial and immediate. The main drawback is that bunkie boards add height to your bed, which requires deeper fitted sheets and can make getting in and out of bed more difficult for some people.
Select a firm, thin mattress pad designed specifically for support rather than cushioning. Look for densely quilted cotton pads or those containing compressed wool rather than soft, fluffy varieties.
Install the pad directly on the mattress beneath your fitted sheet. Unlike thicker toppers, supportive pads add minimal height while increasing the perceived firmness of the sleep surface.
Mattress pads cost $30 - $80, but they only firm up a mattress to a limited extent compared to mattress toppers, which are more effective.
Detach pillow top layers from mattresses where they're connected by zippers to access the firmer core beneath. Some higher-end mattresses feature removable pillow tops specifically designed to allow adjustment of comfort layers.
before attempting removal to ensure you won't void the warranty. This solution costs nothing and provides significant firmness improvement for mattresses with removable pillow tops.
The limitation is that this option only works for specifically designed mattresses with this feature, and removing the pillow top eliminates the cushioning layer that provides pressure relief.
Mattress firmness is important because it ensures proper spinal alignment, prevents back pain, and promotes restful sleep by providing the right balance of support and comfort.
A mattress that's too soft causes your body to sink, creating an unnatural curve in your spine that leads to morning back pain and stiffness.
Supportive mattresses keep your spine in a neutral position and relieve pressure points. This improves sleep quality, reduces pain, and prevents long-term musculoskeletal issues.
Finding the right mattress firmness is especially important for back and stomach sleepers who need more support, while side sleepers typically require slightly softer surfaces to accommodate shoulder and hip pressure. The ideal mattress maintains support while contouring just enough to keep your body properly aligned throughout the night.
To choose the firmness level you need, consider your sleeping position, body weight, and personal preferences. The following table summarizes the recommended mattress firmness levels based on your sleep position and body weight.
| Sleep Position | Body Weight | Recommended Firmness | Benefits |
|---|---|---|---|
| Side Sleeper | Under 130 lbs (59 kg) | Soft to Medium-Soft (3-4/10) | Cushions shoulders and hips, prevents pressure points |
| Side Sleeper | 130-230 lbs (59-104 kg) | Medium (5-6/10) | Balances support with pressure relief at hip and shoulder |
| Side Sleeper | Over 230 lbs (104 kg) | Medium-Firm (6-7/10) | Prevents excessive sinking while cushioning pressure points |
| Back Sleeper | Under 130 lbs (59 kg) | Medium-Soft to Medium (4-5/10) | Supports lower back while allowing slight contouring |
| Back Sleeper | 130-230 lbs (59-104 kg) | Medium-Firm (6-7/10) | Maintains spinal alignment with adequate lumbar support |
| Back Sleeper | Over 230 lbs (104 kg) | Firm (7-8/10) | Prevents excessive sinking that could misalign spine |
| Stomach Sleeper | Under 130 lbs (59 kg) | Medium (5-6/10) | Prevents pelvis from sinking while comfortable for chest |
| Stomach Sleeper | 130-230 lbs (59-104 kg) | Medium-Firm to Firm (6-8/10) | Keeps spine aligned by preventing midsection from sinking |
| Stomach Sleeper | Over 230 lbs (104 kg) | Firm to Extra-Firm (8-10/10) | Provides maximum support to maintain neutral spine position |
Test your chosen firmness for at least 30 nights to allow your body to adjust. Many eco-friendly mattress companies offer sleep trials of 100 nights or more, giving you ample time to determine if the firmness level meets your needs.
