Guides · 9 min read

A child on the top bunk: what the federal standard settles, and what it leaves to you

The bunk bed standard is a page of numbers, and three of them matter on the day the bed goes up: the rail height above the mattress, the gap at the end, and the age of the child who climbs the ladder. The mattress you already own can break the first one.

A bunk bed is the one piece of children's furniture with a federal standard written specifically for it, and the standard is a page of numbers about rails, gaps and mattresses. Three of those numbers matter on the day the bed goes up, and the one that gets broken most often is broken by a mattress you already own. Read against a twin-over-twin frame, the standard settles some decisions for you and leaves the rest to you, and below is which are which.

Two rails, and one of them runs the full length

The upper bunk of any bunk bed sold in the United States must have a guardrail on both sides. The Consumer Product Safety Commission's rule is specific about which one is continuous: the rail on the wall side, or on the side opposite the ladder, runs from one end of the bed to the other without a break, because that is the side a sleeping child rolls toward. The other rail may have a gap for climbing in, and the gap may be no more than 15 inches measured from the end of the bed. Our twin-over-twin frames ship with both rails and the ladder, and the assembly sheet puts the continuous rail on the side you choose; choose the wall.

The rails must be fixed with fasteners that have to be deliberately released, or fittings that need two separate movements to come off, so a child cannot lift a rail out by leaning on it. A rail that lifts out with one tug has been assembled wrong, and the cure is the bolt that was left in the bag.

Five inches above the mattress: the number your mattress can break

The tops of the guardrails must stand at least 5 inches above the top of the mattress. The frame cannot promise that, because the frame does not know how thick your mattress is. A rail that clears a 6-inch mattress by 5 inches clears a 10-inch mattress by 1, and a one-inch rail is a step. The maximum mattress thickness is printed on each bunk bed page, and it is the first figure to read against the mattress you mean to use up top. A thick mattress from the old bed goes on the bottom bunk; the thin one goes up.

The same page of the standard limits the openings at the ends of the upper bunk above the mattress: nothing above the mattress foundation may let the commission's wedge block through, and the block is sized as a stand-in for a child's body. That is a test the frame passes or fails at the factory, and it is another reason the mattress must not sit higher than the frame was cut for: the openings were measured from a mattress of the stated thickness.

The lower bunk, and why it may have no rail

A lower bunk whose mattress foundation is 30 inches or less from the floor needs no guardrail under the rule, and that is the reason most twin-over-twin frames have none below. The standard instead limits the openings in the lower bunk's end structures: a space a 9-inch sphere can pass through has to be tested for whether a child's head could be trapped in it. On our frames those openings are set by the factory; what you decide is the mattress, again, because a lower mattress thicker than the frame expects raises the sleeper toward the upper bunk's slats.

The age of the child, which the frame cannot check

The commission classes children's bunk beds as beds for children 12 and under, and its advice, older than the standard and repeated on its warning labels, is that a child under six does not sleep on the top bunk. The frame carries the label; the decision is yours, and it is the one number on this page the furniture has no part in. A five-year-old who climbs well is still a five-year-old who falls asleep at the top of a ladder.

The other age rule is about the ladder itself. It is fixed to the frame, it is used facing the rungs, and it is not a slide; the reviews that mention a fall mention a child who came down the wrong way round. Put the ladder end away from the window and the ceiling fan, and put nothing on the floor beneath it that a child would land on.

What the frame states about weight

Our twin-over-twin metal bunk bed states a capacity of 400 pounds for each bunk, upper and lower, and the figure is on the card. That is the frame; the slats or the steel grid under each mattress are what carry it, and the commission's long-standing note on mattress supports is that they can be dislodged if they merely rest on ledges, so the assembly sheet's screws for the mattress support are not optional. Retighten every bolt after the first week, when the joints have settled, and again at the start of each school year.

The wall, the ceiling and the window

A bunk bed stands against a wall along its continuous rail, and the wall should be a wall: not a window, whose sill and cord are at the height of a sleeping child, and not the swing of a door. Measure from the floor to the ceiling before the frame goes up and subtract the frame height on the card; a child sitting up on the top bunk wants a foot of air over their head, and a ceiling fan wants more than that. The frame height and the height of the top bunk's mattress foundation are both printed on the page.

The rail clears a 6-inch mattress by 5 inches and a 10-inch mattress by 1. The frame cannot promise the five inches, because the frame does not know how thick your mattress is.

The day the bed goes up

• Read the maximum mattress thickness on the page and put the thinner mattress on top; measure 5 inches from the top of it to the top of the rail.
• Put the continuous rail on the wall side, and put the bed against a wall rather than a window.
• Screw the mattress supports to the frame; do not let them rest on the ledges.
• Keep a child under six on the bottom bunk, whatever the label on the frame says about age.
• Face the rungs on the way down, and keep the floor under the ladder clear.
• Retighten the bolts after a week, and again every September.