A specialist dot and dab fixing with a rigid steel core is the correct choice, such as Corefix Connect. The steel core bridges the void between the plasterboard and the blockwork, transferring the full weight of the boiler to the solid masonry so the plasterboard carries none of it. Unlike a standard frame fixing, which can crush the plasterboard inward as the screw is tightened, Corefix Connect has a built-in shoulder stop that prevents this from happening, leaving the wall surface flat and undistorted after installation. With a Safe Working Load of 55kg per fixing in dot and dab walls, four fixings provide more than enough capacity for a modern domestic boiler.
Secure Boiler Fixing on Cavity Walls
In brief: A gas boiler is one of the heaviest items routinely fixed to a domestic wall, and on a dot and dab or dry lined wall, the gap between the plasterboard and the solid masonry behind it makes standard fixings unreliable. As the boiler’s weight is applied, a conventional plug either flexes in the void or pulls the plasterboard inward, creating an unstable fixing that can worsen over time. For a boiler installation on a dot and dab wall, a steel-cored fixing like Corefix Connect is the correct choice: it bridges the cavity, anchors into the blockwork, and prevents any movement in the plasterboard. With a Safe Working Load of 55kg per fixing, four fixings are sufficient to support the weight of a modern domestic boiler.
Fix Wall Mounted Boilers Safely with Corefix
Of the many items that have to be attached to the wall of a property, a gas boiler is probably the one where a secure fixing is essential. The boiler will be usually be located on an outside wall in the kitchen or airing cupboard or sometimes on a block built internal wall.
Wall fixing a heavy boiler can present problems as building practice since the 1930’s has been to construct the wall with a cavity either between the outer and inner skin or behind a plasterboard finish. The latter is often referred to as a dot and dab or dry lined wall.
A traditional cavity wall presents less of a problem as the inner skin is usually made of bricks or blocks, which offer a good anchor for the fixing as the plug will be fully inserted into the wall.
A dot and dab wall is a different matter because there is a gap between the outer plasterboard finish and the solid wall behind. In this instance the weight of the unit is only partially supported by the plug inserted into the wall with the plasterboard having to support the rest of the load. The greater the load, the higher the risk of the plug deforming or the plasterboard collapsing into the void.
What is required therefore is a fixing that securely bridges this gap. The Corefix Connect range has been particularly developed for this situation. As opposed to a traditional rawl plug, Corefix Connect has a steel core which fits snugly inside the plug.
This steel core creates a strong and inflexible bridge over the gap, spreading the weight throughout the fixing. This means that the unit being attached cannot move as the fixing flexes when the weight is attached and the risk of the plasterboard collapsing is eliminated.
This is vitally important when attaching gas boilers to a cavity wall as the integrity of any pipework can be compromised if the unit is not secure and there could be a major gas leak if the fixing should fail entirely.
Corefix Connect fixings have been tested to a load of 250kg on four fixings and have a safe working load of 55kg per fixing, which is easily capable of securely supporting a modern gas boiler.
The same can be said of other central heating components such as radiators or any other heavy items such as wall hung cabinets, televisions, wall hung sinks and toilets and shelving – see this case study of installing heavy radiators with Corefix Connect.
For more information visit our dedicated downloads page where there is a handy technical datasheet. Corefix Connect is available in Trade or DIY pack sizes from our trusted retailers.
If you have any questions at all, please don’t hesitate to contact us! You can email us or call us for free on 0800 130 3646.
Frequently Asked Questions
Why is fixing a boiler to a cavity wall more complicated than fixing to a solid wall?
On a solid masonry wall, the fixing plug sits entirely within dense brick or block material that grips it firmly on all sides, giving a reliable anchor for the full weight of the boiler. On a cavity or dot and dab wall, there is a gap between the plasterboard surface and the solid masonry behind it. A standard fixing in this situation sits partly in that void, where it has nothing solid to grip against. The weight of the boiler is then shared between the plug in the masonry and the plasterboard face, and the plasterboard is not strong enough to carry its portion of that load reliably over time.
How many Corefix Connect fixings are needed to mount a boiler safely?
A minimum of four fixings is recommended for mounting a boiler to a dot and dab wall, and more should be used for larger or heavier units. Four Corefix Connect fixings in solid brick or blockwork give a combined Safe Working Load of 100kg, which comfortably exceeds the weight of most modern domestic boilers even when full of water. The fixings have been tested to over 250kg without failure in controlled testing, giving a substantial safety margin above the rated figures. If the blockwork is lightweight aerated or thermalite concrete, the Safe Working Load on four fixings is 73kg, which should still be checked against the boiler manufacturer's weight specifications.
Why is a secure boiler fixing particularly important compared to other wall-mounted items?
A boiler is connected to the gas supply and to the central heating pipework, which means any movement or failure in the wall fixing creates risks that go beyond the item simply falling off the wall. If a boiler becomes loose and shifts position, the stress on the pipework connections can cause joints to weaken or fail, potentially resulting in a gas leak or a water leak into the wall. A gas leak in particular is a serious safety hazard. This makes the integrity of the wall fixing not just a structural question but a safety-critical one, and it is one of the reasons boiler installation is legally required to be carried out by a Gas Safe registered engineer.
Can a boiler be fixed to a traditional cavity wall with an inner and outer masonry skin?
Yes. A traditional cavity wall with an inner brick or block skin presents far fewer problems than a dot and dab wall, because the inner skin provides a solid and continuous masonry surface for the fixing to anchor into. Standard good quality masonry fixings of the appropriate size and depth will give a reliable hold in this situation, provided the hole is drilled to the correct depth and the plug engages fully with the blockwork rather than sitting in the mortar joint between courses. The key is confirming which type of cavity wall you are dealing with before selecting fixings, since the two wall types look similar from the surface but behave very differently under load.
What should be checked before drilling into a cavity wall to mount a boiler?
Before drilling, check for electrical cables and water pipes behind the wall using a multi-function detector. In a kitchen or utility room where a boiler is commonly located, pipes and cables are particularly likely to be present behind the wall surface near the intended fixing positions. Confirm the wall type by tapping and if necessary drilling a small pilot hole to check for a void behind the plasterboard. Confirm the cavity depth is within the 45mm maximum that Corefix Connect can accommodate, and check the masonry type behind the board to select the correct Safe Working Load figure for the number of fixings being used. Following the boiler manufacturer's installation instructions for fixing positions and load requirements is also essential before work begins.