Short answer: measure the wall the bed will go against, take off 60 cm each side for getting in and out, and buy the biggest bed that fits in what is left. In a lot of tenement rooms that is a small double (4 ft), and it is a far better bed than people expect. Here is how to work it out.

The sizes

Single 90 x 190 cm. Small double 120 x 190 cm. Double 135 x 190 cm. King 150 x 200 cm. Super king 180 x 200 cm. Those are mattress sizes; a divan base is the same footprint and a bed frame adds anything from a couple of centimetres to twenty, depending on the design, so check the frame's outside dimensions, not just the mattress size.

The tenement problem

The rooms are generous in floor area but awkward in shape. A bay window eats one wall, the press (the built-in cupboard) eats a corner, the door swings into the room, and the fireplace sits in the middle of another wall. The bed usually has to go on the one clear wall, and that wall is often 3 metres or less. Two people need to get in and out on their own sides, so a double at 135 cm plus a bedside each does not leave much.

Small double versus double

Fifteen centimetres does not sound like much, but it is the difference between a bedside table on each side and a bedside table on one. For a couple the extra width of a double is nicer; for one person, or a couple in a narrow room, a small double sleeps two comfortably and gives the room back. The mattress choice is exactly the same, and a small double in a good mattress beats a double in a cheap one every night of the week.

Storage

Tenement flats rarely have enough. An ottoman base, where the whole mattress platform lifts on gas struts, turns the space under the bed into the biggest cupboard in the flat. Drawer divans work too, but check the drawers can open: a drawer on the side that faces the wall is wasted. End-opening ottomans suit narrow rooms best because nothing has to open sideways.

Getting it up the stairs

Three flights of a tenement close with a tight turn on each landing. A divan comes in two halves, so it goes up easily. A one-piece bed frame with a tall headboard may not make the turn, and a pocket-sprung mattress that cannot be rolled is a two-man job that needs the right two men. Tell us the floor and the close when you order and our delivery team will plan it, or say if you would rather a rolled mattress.

Headboards and ceilings

Tenement ceilings are high, so a tall headboard looks right in a way it never does in a new build. If the bed is going against a wall with a picture rail, a floor-standing headboard avoids fixing anything to old plaster.

Every size is on the floor to lie on in Clydebank, and our own Signature Beds are made in Britain in any of them. See beds, mattresses and our bed sizes guide. Delivery is two-man, to the room, up the close.

Paul James Home, Co-op Department Store, Clydebank. Monday to Saturday 9 to 5. 0141 266 0400.