How to Make a Soft Mattress Firmer
If your mattress feels too soft and you sink excessively at night, you can increase firmness safely using a firmer topper, plywood base layer, or strategic replacement without purchasing an entire new mattress. The key is matching the added support to your UK mattress size while preserving fire-safety compliance under the 1988 regulations.
Why Your Mattress Feels Too Soft
Common causes include age-related foam compression, insufficient base support from slats spaced wider than 7cm apart, or a design that prioritises cushioning over support. A soft single or super king can exacerbate back discomfort if your body weight compresses the top layers fully. Before altering anything, rotate or flip the mattress according to the maker’s instructions and check that all bed slats are intact and evenly spaced.
Quick Non-Permanent Fixes
Start with the simplest options that require no tools. Place a firm sheet of plywood or MDF (cut to exact mattress dimensions) directly onto the bed base beneath the mattress. This creates a solid platform that reduces bounce and deep sinkage. Ensure the board is no thicker than 1.5cm to maintain some flex and avoid damaging the bed frame. Another immediate step is to add a thin cotton or wool underlay between the mattress and base to smooth out any pressure points.
Using a Mattress Topper to Add Firmness
A firmer topper placed on top of your existing mattress is often the most practical solution. Choose a latex or high-density foam topper rather than memory foam, which can feel softer. Measure your current mattress size precisely and select an exact matching topper. Aim for a topper no deeper than 5cm to avoid raising the overall sleeping height too much and compromising safety on bunk beds. Always secure the topper with straps or a grippy mattress protector to prevent movement during the night.
For those seeking a balanced upgrade, browse our range of medium firm mattresses if a topper alone proves insufficient. Brands such as Maxitex and Recoil offer models that combine support without excessive cushioning.
Replacing the Mattress Entirely
If temporary fixes do not deliver enough improvement, replacing the mattress with a firmer model is the most effective long-term answer. Look for options labelled firm or orthopaedic that use pocket springs or high-density foam. A Maxitex Foamapaedic Firm Foam Mattress provides consistent support across the entire surface. Similarly, the Komfi Vitality Ultra Firm Foam Mattress uses dense foam to resist deep compression. Check the exact depth on the product page to ensure compatibility with your bed frame and any bunk-bed guard-rail requirements (minimum 16cm clearance above the mattress surface for children over 6).
Consider firm mattresses from Solace+Co or Noomi for natural fillings that maintain rigidity. Avoid soft models entirely; our soft mattresses category is best reserved for side sleepers who need cushioning rather than firmness.
Improving Your Bed Base for Better Support
The bed base contributes significantly to perceived mattress firmness. Slatted bases with gaps wider than 6-7cm allow excessive flex. Switching to a solid divan or adding extra central slats can firm the whole sleep surface. For storage beds, ensure the platform is completely flat when closed. If using a bunk bed, confirm it meets BS EN 747 standards and never exceed the manufacturer’s maximum mattress depth on the top bunk. A firmer base paired with your current mattress often yields better results than a topper alone.
Decision Checklist Before You Act
- Measure your exact mattress size and bed base dimensions.
- Determine your primary sleep position: back and stomach sleepers usually need firmer support than side sleepers.
- Check current mattress age and condition – if over 7-8 years, replacement is often more economical.
- Test any added layer for at least 7 nights before committing.
- Ensure all changes comply with UK fire-safety standards (BS 7177 for mattresses).
- For children’s beds, verify top-bunk guard rails remain at least 16cm above the final mattress surface.
Our soft furnishings and new soft furnishings sections include protectors and underlays that help secure any firmness modifications.
When to Seek Professional Advice
If you experience ongoing pain or the mattress shows visible sagging deeper than 5cm in the centre, the internal structure may be damaged. In such cases, a full replacement from our memory foam mattresses or firm ranges is advisable. Always cross-reference the product page for exact specifications before ordering.
Our picks for this guide
- Maxitex Foamapaedic Firm Foam Mattress – This firm foam mattress resists deep sinkage, making it an ideal direct replacement for an overly soft existing mattress of the same size.
- Komfi Vitality Ultra Firm Foam Mattress – Ultra-firm foam construction provides immediate support upgrade when your current soft mattress no longer offers enough resistance.
- Maxitex Europaedic Traditional Orthopaedic Mattress – Traditional orthopaedic design delivers firmer support across standard UK sizes, counteracting the softness of older mattresses.
- Noomi Bamboo Natural Latex Pocket Sprung Mattress – Natural latex layers add responsive firmness on top of pocket springs, suiting those who want to firm up without losing all cushioning.
Frequently asked questions
Can I use plywood under any mattress size?
Yes, but it must be cut precisely to the mattress dimensions. Thinner 1-1.5cm board preserves some natural flex while firming support. Secure it so it cannot shift, and check your bed frame can accommodate the extra layer without affecting stability.
Will adding a topper make my bed too high?
A 5cm or shallower topper usually adds manageable height. Measure from floor to current mattress top, then add the topper depth. On bunk beds, ensure the final height still leaves at least 16cm from the top of the mattress to the top of the guard rail as required by BS EN 747.
Is it safe to put a firm topper on a memory foam mattress?
It is safe but may reduce the pressure-relieving benefit of the memory foam. A latex or reflex foam topper works better for firmness. Always use a breathable protector between layers and follow the manufacturer’s care instructions to maintain fire safety compliance.
How long do firmness modifications typically last?
Plywood bases can last many years if kept dry. Toppers compress over 12-24 months depending on density and usage. A full firmer replacement mattress from brands such as Maxitex or Noomi typically maintains its stated firmness with regular rotation.
Can these methods be used on children’s mattresses?
Only if the final setup meets all safety standards. Top bunks must retain 16cm guard-rail clearance above the mattress. Use mattresses no deeper than the bed maker specifies. For cot or toddler sizes, choose UK-compliant firmer models and never add loose boards that could create gaps.