Sofa Beds Glossary: Every Term You Need to Know

A sofa bed is judged on three things: the mechanism that turns it into a bed, the mattress or cushioning you actually sleep on, and the frame and fabric that hold it all together. Once you understand the handful of terms used to describe those three areas, product pages become far easier to read and comparisons start to make sense.

This glossary gathers the words you will meet while browsing modern sofa beds UK shoppers ask us about most often. We have grouped them by theme rather than alphabetically, so related ideas sit side by side and you can see how each one affects comfort, space and everyday use.

Mechanism and Action Terms

Action. The general word for the way a sofa converts into a bed. When a retailer talks about a “smooth action”, they mean the conversion needs little effort and runs without catching or jolting.

Click clack. A mechanism where the backrest folds down flat to meet the seat, creating a single level sleeping surface. You push the back until it clicks, then lower it. The name comes from the sound the hinge makes. There is no separate mattress: you sleep on the seat and back cushioning.

Pull out. A mechanism where a folded metal frame and mattress sit hidden beneath the seat cushions. You remove the cushions, pull the frame forward and it unfolds into a bed. This style usually offers a dedicated mattress, which many people find more comfortable for regular guests.

Bifold and trifold. These describe how many sections a pull out mattress folds into. A bifold folds once, so the mattress tends to be thicker and has fewer creases. A trifold folds twice, which lets it fit into a shallower sofa but can introduce more joins in the sleeping surface.

Fold out. Often used interchangeably with pull out, though some makers reserve it for designs where the seat itself flips forward to reveal the mattress. Always check the product images to see exactly how the conversion works.

Drop arm. A sofa where one or both arms lower to create a longer lying space. Drop arm designs work well as a daytime lounger and an occasional bed for one person.

Daybed. A frame designed to be sat on and slept on without any conversion. Some daybeds include a trundle underneath to create a second sleeping space.

Trundle. A low, wheeled bed base that slides out from under a daybed or sofa. It gives you an extra single sleeping surface without adding visual bulk.

Futon. In UK furniture terms, a futon usually means a simple frame with a thick, flexible mattress that folds into a seat. The mattress doubles as the seat cushion, much like a click clack.

Shape and Layout Terms

Corner sofa bed. An L shaped sofa where one section converts to a bed. These suit open plan rooms where you want generous everyday seating.

Chaise. The extended seat section on a corner or chaise sofa, long enough to stretch your legs along. On many sofa beds the chaise also contains storage.

Storage chaise. A chaise with a lift up seat and a hollow compartment underneath. It is a sensible home for spare duvets and pillows, so bedding stays close to where it will be used.

Reversible chaise. A chaise that can be fitted on either the left or right side, which helps if you move home or rearrange the room.

Armless. A sofa bed with no arms, which saves width and makes the sleeping surface feel longer. Click clack designs are often armless.

Sofa bed chair. A single armchair that converts into a narrow bed. Useful for a box room, study or teenager’s bedroom.

If you are still deciding between a convertible piece and a standard settee, it helps to browse our wider modern sofas UK sale collection to compare shapes, arm styles and seat depths before committing to a mechanism.

Mattress and Comfort Terms

Sleeping surface. The flat area you lie on once the sofa is converted. This is the measurement that matters for comfort, so check it separately from the overall sofa width.

Mattress depth. The thickness of the mattress. A deeper mattress generally gives more cushioning between you and the frame, which matters most on pull out designs.

Pocket springs. Individual springs, each sewn into its own fabric pocket. Because they move independently, they respond to the body more precisely and reduce the sense of a partner moving beside you.

Open coil. A system where springs are linked together by a continuous wire. It is a traditional construction that offers firm, even support.

Memory foam. A dense foam that softens with body warmth and moulds slowly to your shape. It is often used as a top layer to make a thinner mattress feel more substantial.

Reflex foam. A firmer, springier foam that returns to shape quickly. It is common in click clack seats and in mattress cores.

Fibre wrap. A soft layer of polyester fibre wrapped around foam cushions. It adds a gentle, slightly relaxed feel to the seat and back.

Firmness. How much a mattress or seat resists your weight. Labels such as soft, medium and firm are a guide rather than a precise scale, so read descriptions alongside customer comments.

When a sofa bed will be used often, some households add a separate topper or choose a frame that accepts a standard mattress. Our range of modern mattresses UK sale gives a useful sense of the different constructions and how they feel. We look at foam layers in more depth in our piece on memory foam mattresses in UK sofa beds.

Frame and Construction Terms

Frame. The internal structure that holds everything in place. Common materials include solid hardwood, engineered wood such as plywood or chipboard, and metal. A well built frame keeps the sofa stable through repeated conversions.

Kiln dried. Timber that has been dried in a controlled oven to reduce moisture. Drying helps prevent warping and movement over time.

Webbing. Strong elastic or woven straps stretched across the seat frame to support the cushions. Webbing creates a slightly bouncy seat.

Serpentine springs. Also called sinuous springs, these are S shaped wires running front to back under the seat. They provide firm, durable support and are widely used in sofa construction.

Deck. The base area beneath the seat cushions. On a pull out sofa bed, the deck often hides the folded bed frame.

Self assembly. Some sofa beds arrive with legs or backrests to attach. This is usually straightforward, but it is worth knowing in advance so you can plan the day of delivery.

Legs. The feet that raise the frame off the floor. Wooden and metal legs give a lighter look than a skirted base and make cleaning underneath easier.

Fabric and Upholstery Terms

Upholstery. The fabric or leather covering and the padding beneath it.

Woven fabric. Fabrics made by interlacing threads, such as linen look weaves, tweeds and textured basketweaves. They tend to hide everyday marks well.

Velvet. A fabric with a short, dense pile that catches the light. It feels soft and looks rich, though it shows the direction of the pile when brushed.

Faux leather. A synthetic leather alternative. It wipes clean easily, which some families find practical.

Martindale rub test. A standard test that measures how well a fabric resists abrasion. Generally speaking, a higher result suggests a more hardwearing fabric, which is worth considering if the sofa bed will be your main seating.

Removable covers. Cushion covers that unzip for cleaning. Always follow the care label, since some covers need dry cleaning rather than washing.

Fire safety label. Upholstered furniture sold in the UK must meet the Furniture and Furnishings (Fire) (Safety) Regulations. A permanent label confirming compliance is usually attached to the frame.

Size and Measurement Terms

Overall dimensions. The width, depth and height of the sofa when closed. Use these to check it fits the room and through doorways.

Open dimensions. The length and width of the sofa once it becomes a bed. Allow clear floor space beyond this so guests can get in and out comfortably. Our guide to sofa bed open dimensions for UK rooms explains how to plan this properly.

Seat height and seat depth. Seat height is measured from the floor to the top of the seat cushion. Seat depth runs from the front edge to the backrest. Together they decide how the sofa feels to sit on every day.

Small double and double. Common UK sleeping sizes. A small double is narrower than a standard double and suits one adult or a couple for short stays. A standard double gives more room for two.

Access measurements. The widths of doorways, hallways and stair turns between the front door and the room. Measuring these before ordering is one of the simplest ways to avoid a difficult delivery.

Putting the Terms to Work

Knowing the vocabulary helps you ask better questions. If you host guests a few times a year, a click clack or futon may be all you need. If someone will sleep on it every week, a pull out design with pocket springs or a deeper mattress is worth considering. If storage is tight, a chaise with a lift up seat solves two problems in one piece.

Start with the room: measure the space, the open length and the route in. Then decide how often the bed will be used and by whom. Finally, choose a fabric that suits your household, whether that means a tight weave for busy family rooms or a soft velvet for a quieter snug.

You can explore all of these styles, along with matching living room furniture, at Furniture in Fashion, where we bring together modern designs for homes across the UK.

Frequently Asked Questions

What is the difference between a click clack and a pull out sofa bed?

A click clack folds its backrest down to create a flat surface, so you sleep on the seat cushioning. A pull out hides a separate folding frame and mattress under the seat, which you draw forward to make the bed.

Which sofa bed mattress is most comfortable for regular use?

For frequent sleeping, a deeper mattress with pocket springs or a memory foam layer usually feels more supportive than thin foam. Comfort is personal, so read the firmness description and mattress depth carefully.

What does the open length of a sofa bed mean?

It is the distance from the back of the sofa to the end of the bed once fully opened. Add space around it for walking so the room still works when the bed is in use.

Do sofa beds in the UK need a fire safety label?

Yes. Upholstered furniture sold in the UK must comply with the Furniture and Furnishings (Fire) (Safety) Regulations, and a permanent label is normally fixed to the item.