Sofa Bed and Day Bed Replacement Mattresses

A sofa bed mattress has to do something no other mattress does: fold into a cavity and let the sofa close. That constraint decides the depth, the material and, usually, the price.

Measure the mechanism, not the mattress

Open the bed fully and measure the metal frame the mattress sits in — the sprung mesh or slatted platform, not the old mattress on top of it. Take:

• Width and length of the frame, at the narrowest points.
• The depth the sofa will close on. Fold the mechanism away with a tape measure standing in the cavity, or measure the old mattress and treat that as your ceiling.
• Where the fold lines are, and which way each section bends.

That third point is the one people forget. A two-fold and a three-fold mechanism need different constructions, and a mattress made for the wrong one will not sit flat.

Depth is decided for you

Most sofa beds close on 10 to 14 cm. Going thicker is the most common mistake: the sofa will not shut, or it shuts under strain and destroys the mechanism over a few months.

If your current mattress is 10 cm, order 10 cm. The comfort improvement comes from what it is made of, not from finding an extra two centimetres.

What to make it from

At this depth a spring unit is out. The choice is between foams, and it matters more than usual because there is so little material doing the work:

• High-density foam. The standard answer. Look for a support grade rather than a cheap filler foam — in 10 cm there is nowhere for a poor foam to hide.
• Latex. Noticeably better at this depth because it resists rather than bottoming out. Heavier, which matters on a mechanism you lift.
• Memory foam. Avoid as the only layer this thin. You compress straight through it onto the frame.

Whatever you choose, a folding mattress lives folded. Materials that take a permanent set will hold the crease; latex and higher-density foams recover better.

The bar you can feel

The classic sofa bed complaint. A support bar running under the mattress is felt through anything thin. Two fixes: a slightly denser foam, or a thin topper laid on when the bed is made up and stored away in the day. The second works better and costs less.

Day beds are a different job

A day bed does not fold, so the depth constraint disappears and the constraint becomes the surround. Measure from the platform to the top of the side rail — a day bed usually looks wrong with anything deeper, because you sit on it as a sofa. Fifteen to eighteen centimetres is the usual answer, and a firmer build sits better for daytime use.

Our SlimFit at 16 cm suits a day bed as it comes; for anything non-standard we cut it.

Common questions

Can you make a folding mattress in sections?

Yes — tell us where the folds are and which way they bend.

Will a custom sofa bed mattress fit the original cover?

Only if it is exactly the original dimensions. Say so if you intend to reuse the cover.

How long will it last?

Less than a bed mattress used the same number of nights, because folding is hard on any foam. For occasional guest use, many years.