RSJ Oak Covers – Technical


A simple guide to the measuring, installation and other considerations when buying an oak cover.

Further in-depth advice and help can be given by calling 01423 593794


As oak covers can be used to disguise many items, the following instructions have been written as if you are covering a steel RSJ on a flat ceiling.

A tolerance should be made of 10mm in both the drop and width of the RSJ.  This is to allow any deviation in the manufacturing of the oak cover and any deflection in the RSJ.

For example, an RSJ measuring a standard 203mm x 203mm would need to have an internal dimension of the oak cover of 213mm x 213mm.   The covers can be made to any width and drop.

Your oak cover is manufactured from 27 to 30mm thick oak planks depending on stock availability and therefore the external dimensions of the above example would have a drop of 235-238mm and a width of 267-273mm

Calculations are:

Drop 203mm RSJ + 5mm tolerance + 27mm to 30mm thick oak = 235-243mm in total

Width 203mm for the RSJ + 10mm tolerance (5mm each side) + 2 planks at 27mm to 30mm thick oak = 267-273mm in total


Installation of oak covers is normally a 2 or more person job. This depends on the length, location and dimension of the cover.

Working on the same example from above, there is a need to secure [tipso tip=”Noggins can be referred to as softwood pieces, cut to fit within an aperture.”]noggins[/tipso] between the top and bottom [tipso tip=”Flanges are the top and bottom horizontal pieces of steel. The ‘Web’ is the single vertical piece of steel.”]flanges[/tipso] of the RSJ.

These can be set at 800mm centres along each side down the length of the cover. Ideally, another noggin should be placed at the ends.   Important:  mark the location of these noggins on the ceiling as they won’t be visible when the oak cover is guided in to place.

Every oak covers come with a specially shaped drill bit and matching oak pellets. This drill bit is used to create a hole in the side of the cover to accommodate a [tipso tip=”Avoid using plain steel screws. A recommendation would be to use an M5x50 or M5x70 yellow passivated screw depending on the size of your cover.”]suitable screw[/tipso].

The head of the installed screw is then disguised with the oak pellet as shown in the diagram on the left-hand side.  Align the grain on the pellet to match that shown in the oak cover.  This pellet can be left as a feature or chiselled flat and coloured using the supplied matching wax stain.

Extra Long Covers

Your RSJ oak cover is made from [tipso tip=”This oak has a very low moisture level enabling the oak to remain stable.”]kiln dried oak[/tipso] planks.

These planks vary in length although the majority are between 3m and 5m. Sometimes longer planks up to 8m can be sourced.

Your RSJ oak cover can be produced in one length regardless of the available stock. This is accomplished by staggering the base and side pieces to create longer planks.

It is sometimes necessary to disguise the join with an oak strap that can be incorporated into the design of the cover providing a feature and giving more character.

oak cover with straps
Contemporary Oak Cover with Straps

Other Considerations

Is your cover going against a pitched roof or vaulted ceiling?

Do the left and right-hand sides need to extend beyond the base piece?

Do you need 2, 3 or 4 sides?

Are the side walls of an even height?

For expert advice, further prices and general help, call 01423 593794