Help with Load Rating
Wall fixings and hooks are a structural element that are relied upon to safely secure objects. Fixings are designed to be suitable for light, medium or heavy loads and have recommended maximum weights that they can support.
These maximum loads are based upon the failure loads observed during testing. Maximum recommended loads are more commonly referred to as Safe Working Loads (SWL). By never exceeding the SWL the installer can be sure, provided the installation instructions have been followed, that the selected fixing will not fail.
Safe Working Loads are calculated from the test failure load. So, for instance, a fixing that failed at 50kg during testing is likely to have a SWL of less than 25kg.
SWLs are the maximum recommended weights of the items being fixed. They need to be treated with caution as they will be significantly reduced if the condition of the wall being fixed into is poor or if a cantilever bracket is being fitted.
Using a fixing or hook with too low a SWL can result in a catastrophic failure, with potential damage or injury being caused as a result.
Traditional vs Specialist Fixings for Plasterboard Walls
Without appropriate fixings, you should only hang very light objects directly on a plasterboard wall as the plasterboard itself is not strong. This can be done with nails hammered in at an angle (for an optimum secure fix) or specialist plasterboard fixings. Nail based hangers can typically support loads of up to 5kg, provided they do not protrude far from the wall. Specialist plasterboard fixings can support much greater loads, in some cases up to 50kg+.
A bracket that protrudes out from the wall will put a significantly larger force on the fixing than an item of the same weight that is fixed flat to the wall. The greater the distance that the item is extended from the wall, the more the load forces are increased, placing greater stress on the anchor point (this is known as a cantilever force). These types of fixtures must be used with extreme care with a ‘belt and braces’ approach being taken.
What is a Cantilever Force?
A cantilever is a beam supported only at one end, with a load carried over the overhanging. This is in contrast to a simple-supported beam, which is supported at both ends. Cantilevers provide a clear space underneath the beam without any supporting columns or bracing.
Examples of cantilever installations are swing out cantilever TV brackets, full motion cantilever TV brackets, floating cantilever shelves, cantilever kitchen cabinets and any other item or fixture that protrudes from the wall, without the protruding end being supported.
What Can You Hang on Plasterboard?
It is possible to mount items of various sizes and weights on plasterboards, providing you use the appropriate method of mounting or hanging. Light objects weighing up to 5kg can be mounted without any additional reinforcement. Thus, simple frames for photos, pictures, calendars, medals etc. can be mounted directly on the board with a simple nail.
However, heavier items with larger dimensions require the use of more sophisticated wall fixings, such items include flat screen TVs, cabinets, bathroom fittings, large mirrors etc.
The loadings supported by single fixings in plasterboard are clearly stated on the product packaging (also see the ‘Fixing Selector’!) Typically a single plasterboard will support a weight of up to 30kg on a single fixing, provided it has a center of gravity (centre of mass) not more than 20cm from the wall.
How Can Fixings Pull Out of the Wall?
There are two main forces that anchors or fixings need to resist:
1. Pull Forces: These are forces that pull in the same direction as the fastener is fitted. The force pulls along it’s axis.
2. Shear Forces: These are forces that act against the side of the anchor. The force is exerted at right angles to the axis of the anchor.
How Does the Wall Material Affect the Security of the Wall Fixing?
The material (or substrate) that you are fixing into will also effect the integrity of the fixing. It is important to bear in mind that each material has a different load capacity. For instance, the load capacity of a piece of insulation board will be vastly different to that of a concrete block. As previously stated it is possible to fix light weight objects to plasterboard with standard fittings but heavier items would require either specialist platsterboard fixings or for the wall (substrate) itself to be reinforced ensuring a safe and secure fixing.
Typical Load Capacity by Material
- Concrete – 110kg
- Full brick – 62kg
- Solid silicate blocks – 125kg
- Aerated concrete ≥ PB2, PP2 – 10kg
- Aerated concrete ≥ PB4, PP4 – 42kg
- Ceramic blocks – 25kg
- Hollow silicate blocks – 70kg
- Plasterboards ρ ≥ 0.9 kg / dm3 – 25kg
- Plasterboards 12.5 mm – 15kg
- Ceramic blocks Tramezza Doppio UNI 19 – 15kg
Contact the Wall Wizard team via our live chat where we will be happy to advise should you have any queries.