A lift-up bed with storage underneath is a very practical solution for small flats and children's rooms: duvets, seasonal clothes and suitcases stay out of sight. Its everyday comfort, however, comes down almost entirely to one detail: the gas struts that lift the base. Chosen correctly, they let the mattress and base rise with a light pull and lower gently. Chosen wrongly, the bed is either a struggle to open or springs up on its own.
How a gas strut works
A gas strut is a cylinder filled with pressurised gas and a rod that extends from it. The gas constantly pushes the rod out, and that force works against the weight of the base and mattress. When the bed is lifted, the strut takes most of the weight and the person supplies only the small difference. When it is lowered, the strut slows the movement and stops the base from slamming down.
Strut force is given in newtons (N) and is usually printed on the strut. Beds use struts in pairs, one on each side, so the total force is the sum of the two. How a strut performs also depends on its mounting points, that is, the geometry of the mechanism: struts of the same force can feel different on different mechanisms.
What the force depends on
When choosing struts, the total weight to be lifted is considered: the base itself, the mattress, and the bedding, duvet and pillows on top. The mattress is usually the largest part of this weight, and mattresses vary a great deal. A thick, multi-layer pocket-sprung mattress can be much heavier than a light foam one, so two mattresses of the same size may need different struts.
Bed size matters too: a double bed's base and mattress weigh more than a single's. That is why manufacturers offer struts in different force ratings for bed mechanisms, and the choice is made according to the specific mattress weight and bed size. The best approach is to tell the maker the model or weight of the mattress you will use when ordering.
Signs of struts that are too weak or too strong
If the struts are wrong, you notice quickly in daily use:
- Too weak: the base is heavy to lift, does not stay up, slowly sinks and may drop when released.
- Too strong: you have to press down to close the base, it rises by itself when released, and the bed does not stay firmly shut.
- Balanced: the base rises with a light pull, stays steady when open, and closes gently with little effort.
Overly strong struts are not just annoying. When a closed base is constantly pushed upwards, the parts holding the mattress and the fixings stay under tension, which wears the mechanism out faster.
The quality of the mechanism itself matters too. However well the struts are matched, if the metal arms holding the base are thin and the joints loose, the base twists and creaks as it rises. In a good mechanism the arms are sturdy, the joints precise, and the base lifts evenly on both sides. When ordering, it is worth asking what weight the mechanism is rated for and comparing that with the mattress.
When the mattress changes and as years pass
Changing to a different mattress a few years after buying a bed is common. If the new mattress is much heavier or lighter than the old one, the struts should be changed too, or the problems above will appear. It is not a difficult job: struts are usually removed with a few fixings and replaced with a model of the same length but a different force.
Over time a gas strut can also slowly lose pressure. If a base that once lifted easily becomes heavy and will not stay up years later, that is a sign of worn struts, not a problem with the mattress. Replace both struts together so there is no difference in force between the two sides.
Safety and care
- In a child's room, do not let the child climb into the storage box while the base is raised.
- Do not keep using a base that will not stay steady when open; have the struts checked.
- Do not oil, scratch or paint the strut rod, as this damages the seal.
- Ventilation gaps in the base let air circulate in the storage box and prevent damp building up under the mattress.
Zaferoglu Mebel makes bedroom furniture to order and works with brands such as Blum for hardware. The strut force for a lift-up mechanism is chosen once the bed size and the mattress to be used are known.
