Selecting the right expansion joint cover for your application may not be as easy as you think and can cause major problems if not done properly. A lot of thought has to be put into the selection process, as the majority of expansion joint cover failures are caused by incorrect product selection. Any mistakes can be extremely expensive to put right!
With this blog post we hope to help you select the right cover for the right application first time, every time.
Step 1: Understand the movement requirements
The most important part of selecting the proper expansion joint cover is to understand the movement requirements. Confusion can be caused as manufacturers convey movement in different ways.
Movement can be shown in the following ways:
- as an overall movement
- as a percentage of the expansion joint width
- or more usually as a +/- movement.
A 50mm nominal expansion joint with an anticipated expansion and contraction of 25mm could be shown in the following way:
- 50mm +/- 25mm
- 50mm with a total movement of 50mm
- 50mm +/- 50%
Each manufacturer means the same thing, but each is describing the allowable movement in totally different ways.
We recommend that when the engineer tells you the joint width, you ask them fore the minimum and maximum dimensions at full movement.
The structural engineer will indicate the location of the joints and the joint width needed for movement to occur. Our experience tells us that the width provided by the engineer is typically the movement needed and is not necessarily the joint width required for the covers and/or fire barrier systems so it is worth checking exactly what they mean.
Step 2: Size the joints properly
Once the movement requirements are understood, the joints can be sized properly to accommodate the expansion joint covers.
Most joint covers have components that take up space in the joint opening, and fire rated floor and wall conditions will require a fire barrier, it’s important to remember that these materials will not allow a joint to close to 0mm without damaging the system or surrounding construction. So to be able to accommodate these items you need to work together with the manufacturer to size the joint accordingly, to both meet the movement requirements and accommodate the desired joint cover systems and the associated accessories.
It’s not uncommon for joint sizes to increase on each floor as you go up a building (with the roof having the largest joints). To save time and confusion later, we recommend grouping certain floors together in order to reduce the number of different sized joints required.
Exterior joints that run up the side of a building should always be the same size from the roof to the ground. Any joint size changes on the exterior result in unsightly transitions and difficulties in maintaining weather protection.
Step 3: Consider joint locations and application requirements
When selecting cover systems, it is important to consider their location and usage before a selection is made. Generally the floor cover application is the element most affected by the the intended usage. We recommend starting with the floor cover and progressing from there.
- Is hygiene important? – In areas where hygiene is an important consideration like hospitals, flush gasketed covers are often installed for their ease of cleaning.
- Is durability an issue? – In high traffic areas such as retail environments the best choice is an all metal cover that is hard wearing and tamperproof. Heavy duty options are often available for areas with very high traffic such as airports where heavy rolling loads are often passed over covers.
- Will the cover be used in a car park? – In areas like car parks heavy duty rubber options are often used, for their durability and ability to cope with high rolling loads.
- Is moisture an issue? – In areas where moisture ingress is an issue such as sports stadiums etc. special waterproof joints are available, or moisture barriers can be incorporated into standard covers.
- Is fire integrity an issue? – In most cases fire barriers can be incorporated with an expansion joint cover to maintain fire integrity. Making sure that the barrier does not impede the movement of the joint.
Step 4: Identify adjacent surface finishes
Will the joint cover be located in a hidden area or in a highly visible area (such as a lobby), where aesthetics are more important?
Form and function have often been in conflict with the design and use of expansion joint cover systems. Improvements in function have often come at the expense of aesthetics, and vice versa.
Traditionally trying to conceal expansion joint covers with surface finish in-lays often led to thicker joint cover assemblies. These thicker assemblies resulted in obstacles for wheeled equipment.
As technology and joint cover design has improved, it is now possible to conceal wider cover plates without affecting their functionality. Today, a wide variety of joint cover systems are available to meet form and function requirements, incorporating anything from vinyl floors to solid stone floor tiles.
When selecting expansion joint cover systems, consideration should be given to the adjacent floor and wall finishes. Most finishes can be integrated into the cover assembly for maximum harmony with the surrounding design elements, minimising the visual impact of the joint covers.
Step 5: Installation Method
The installation method for the chosen expansion joint cover really depends on your aesthetic considerations and the required movement the cover has to accommodate.
There are 2 methods / types of joint to choose from:
- Surface mounted joint cover
- Recess mounted joint cover
Surface mounted joint covers are typically smaller, single gasketed models, installed in areas where a small lump in the floor surface isn’t an issue. Surface mounted joint covers are best suited for retrofit situations for their simple installation with no requirement for a blockout to be formed or cut. For example our GFPS series is quite popular in retrofit Hospitals as it allows vinyl floor finishes to butt up to the joint cover, which can be sealed with mastic to help with infection control.
Recess mounted joint covers are typically larger in construction, and can incorporate single or double gaskets. The main difference with the recess mounted joint covers is the requirement for a blockout to be formed prior to installation. It is essential to specify and correctly form the blockout early in the process, as any errors can be very costly to put right.
When forming a blockout we recommend that the recess be formed a minimum of 5mm deeper to allow for levelling prior to installation and we also recommend using a non-shrink, self-levelling bedding compound to form a structurally sound base under the EJC.
We hope our 5 step process is useful, once you have run through all 5 steps you can use our EJC selector tool which will show you which of the products in our range will best suit your application. Click here to give it a go.
CS have been manufacturing and installing expansion joint covers for more than 40 years. We offer a comprehensive range of joint covers and support you throughout the entire process from joint cover selection right through to the installation.