Second Fix Boxings and utility cupboards
Sometimes during the construction process, utilities such as pipes and cables must be installed after the plastering stage, generally being surface mounted or otherwise visible within a room. In these instances, its not possible for them to be boxed in before the plastering. As such, a second fix boxing must be assembled to cover these utilities. Quite often, components that are tidily out of sight when boxed in, but also require intermittent access, such as fuse boards of underfloor heating manifolds are better suited to have a small second fix utility cupboard formed around them.
What are second fix boxings?
A second fix boxing is a type of boxing that is installed during the second fix stage, after the plastering has been completed. A first fix boxing is formed before the plastering stage, and incorporated into the plastering. As such, a second fix boxing is formed from finished materials - typically MDF - and must be scribed into the surround surfaces to create a professional finish. They are generally formed through the use of planed timber battens that are faced with a finished sheathing material, not too dissimilar from the formation of first fix boxings. Seeing as they are not integrated into the surround plaster work, second fix boxings should be minimal in size to keep them as discrete as possible.
Utility cupboards are a type of second fix component that are formed around utilities that cannot otherwise be hidden. For components that require access, such as fuse boards or central heating manifolds, custom made cupboards can be formed with doors that allow access. Both second fix boxings and utility cupboards are typically formed from finished materials such as planned 2”x1” batten, MDF sheets, or interior panelling. These finished materials are an appropriate choice for internal applications, as they can be easily decorated. In many older bungalows in the UK, fuse boards can be found above the front door of the property. Moving the fuse board requires a specialist from the electricity component, along with a substantial cost. As such, in many instances during bungalow renovation or loft conversions, the fuse boards are left in place and simply boxed in with a tidy MDF cupboard.
These cupboards are a common custom component that are used to house unsightly utilities that still require access. Generally speaking, they are simple box shapes, though depending on their location they may be irregularly shaped. Depending on the overall width of the cupboard, they may feature a single door, or a pair of doors. When creating these cupboards, we try to keep them as small as possible, and as tight to the utility as we can to reduce the overall dimensions.
To create these custom cupboards, the process is very straightforward, and is as follows. To begin, a batten frame must be established around the component to provide a mounting point for the boxing. The boxing will be formed on the ground, with the doors housed within, and subsequently lifted onto the wall over the component and secured to the mounting battens. A small tolerance can be left between the inside of the battens and the utility. It’s important that these surround battens are installed square to one another, as the through section of the box will also posses square corners. Once fixed to the wall, the dimensions of the surrounding frame must be taken. To prevent the joins in the panels from being seen from the front, the front face of the box will be the full size of the frame, plus the thickness of MDF on all sides.
A tape measure can be used to determine how deep the box will be. The side panels of the box will be cut to the depth of the wall to the front of the utility, plus 15mm. This provides a 5mm tolerance for scribing and a 10mm gap between the front of the utility and the back face of the front piece of the box once installed. All of the surrounding pieces should be cut to the same width. On the back face of the front panel, the thickness of the side panels are measured in from the sides all the way around. A batten frame is fixed on the inside of this line, to provide a fixing for the side panels to be mounted to. The side panels can then be attached to complete the box. The box can then be lifted over the utility to ensure a correct fit. The surrounding panels should slide neatly over the mounting battens, and the box should be deep enough to make contact with the wall. If required, a pencil can be used to mark a consistent scribe all the way around the box so that it fits tightly to the wall.
At this point, all that is left to do is to cut the doors out of the front panel. The location for the door/s can be marked on the front panel, leaving enough room around the margin if possible to attach a batten on the inside of the box once the doors are cut out. Using a rail saw or a skill saw, the door can be cut, making sure not to overcut the corners. A handsaw can be used to finish the corners. With the door removed, we can clean up the corners and the edges of the cuts. Due to the small margin requirement of the door/s in the opening, the saw blade kerf is typically sufficient. If not, a few passes of a plane around the edges of the door will reduce it to the correct size. If the offcut is to become two doors, simply cut it in half again directly down the middle. From here, a supporting batten for the hinges can be added to the back side of the hinge side of the doors. Chop in the hinges as normal and ensure that the door closes in the opening with a good margin. A magnetic stop to secure the door and a small knob are typical features of a box like this. With the door cut out and installed we can slide the box over the battens attached to the wall and secure it in place.
What are the criteria for the installation of a second fix boxing?
All of the components should be installed plumb and level where applicable. The panelling or MDF sheets that form the boxings or cupboards should be cut neatly as the raw edges are always on show. Materials that meet each other at joins or corners should be flush with each other, as again they are on show. There should be no gaps present in the boxings or cupboard assemblies. The edges of panels that come into the surrounding surfaces should be scribed to fit with a minimal tolerance. Suitable fixings and adhesives should be used to assemble the boxing.
How are second fix boxings formed?
In application, the overall assembly of a second fix boxings is similar in principle to the formation of a first fix boxing. Batten frames are assembled from finished 2”x1” batten in order to create the frame work of the boxing. These battens are joined together through the use of smaller screws or suitable nails, and are secured to the surround surfaces accordingly. The sheet material is cut to fit and installed over the face of these batten frames. Battens should be installed behind the joins of these materials for additional stability. It goes without saying that all of the standard criteria such as plumb, level, and square are also relevant here. Once assembled, the finished MDF surface will be primed and painted. As such, any screws installed should be countersunk to allow the heads to be effectively filled. Additionally, any corners should have the sharp edge taken off of them, with any joins in the MDF being sanded or planned down flat to allow the transition to be filled seamlessly.