Building movement can be caused by the following aspects:
• Thermal Expansion or Contraction Movement caused by the structure expanding and contracting with temperature changes, or shrinking as it dries out
• Building settlement Movement caused by the dead and live loads of the structure on the supporting foundations
• Wind Sway Movement caused by the effect of strong winds on the structure, which is more pronounced on tall buildings
• Seismic Activity Multi-directional movement caused by seismic events, can be significant depending on the magnitude of the seismic activity.
Taking into account the type of movement you can expect within your building, you need to choose the correct Expansion Joint Cover.
Covers are used as expansion joint gap covers for areas that experience movement within structures for example in construction joints in concrete slabs. Buildings are designed to allow movement in response to various forces including thermal expansion and contraction, long-term shrinkage of structures, as well as seismic activity in some cases. The covers are installed over these areas of movement called expansion joints, which are sometimes also referred to as movement joints, structural joints, isolation joints, control joints, or seismic joints.
Omax’s mechanical expansion joints are specifically designed to suit the conditions of different environment; accommodating regular thermal contraction and expansion of building materials during seasonal variation. As global temperatures rise and changes to environmental conditions become more extreme, the installation of expansion joints in buildings has become integral to the engineering design of structures built for different conditions.
Operating internationally for over 20 years, we also have the knowledge, expertise, experience and on-ground presence to assist in your international market, no matter where your project is located.
Choosing an expansion joint cover manufacturer that can help you specify the correct expansion joint cover for your project can take away a lot of the headaches and risks typically associated with expansion joints.
In this article we explain eight key attributes to consider when choosing an expansion joint cover manufacturer.
1. Trust – Trust is vital when it comes to expansion joint covers as you need to trust that a manufacturer’s expansion joint cover supplied will perform to specification. Expansion joint cover problems can be costly to put right, as replacing faulty expansion joint covers and fixing any cracking or structural damage will far exceed the original cost of the expansion joint covers.
2. Experience – Before choosing a manufacturer supplier, ask to see case studies from similar projects to yours or request a site visit. A site visit will allow you to see an expansion joint cover in action, however site visits aren’t always possible due to time constraints, so case studies are the next best thing. Additionally, requesting contact details and talking to existing clients from the manufacturer can also be helpful.
3. Attitude – Manufacturers should be there to help you, providing information and assistance when you need it. If you’re unsure of what expansion joint cover to use in your project, ask the manufacturer what they recommend. A good manufacturer will be more than willing to help, offering suggestions that could not only save you money on the cost of the joint cover, but also in maintenance costs later down the line.
4. Manufacture quality – Choosing a good quality product is always important, but especially so with expansion joint covers. An expansion joint cover failure can be very costly, often leading to permanent structural damage. Look for a manufacturer with a track record of supplying expansion joint covers to a wide range of high profile projects.
5. Warranty – Warranties give a clear indication of a manufacturer’s confidence in their products. Look for a warranty of two years or more when choosing your manufacturer; it should give you confidence that the products will be of a good quality.
6. Operations – When looking for a manufacturer you should investigate their product supply operations. Do they manufacture to order, employ a just-in-time stock policy, or do they hold stock? A company that holds stock can give you confidence that you will receive your product on-site and on time, avoiding the delays that can add unnecessary cost to a project.
7. Range – A key question is whether the manufacturer has a wide range of products to choose from? If not you run the risk of being pigeonholed into an inappropriate choice of joint cover, because there isn’t a model that fits your needs. Every project is different, so it’s important to be able to choose from a large range of expansion joint covers to ensure the right product is selected for your project. Experienced manufacturers may also be able to adapt standard expansion joint covers to suit requirements.
8. Knowledge – Knowledge and experience really go hand in hand; but manufacturers should know everything about their products, how they perform, where they can (and can’t) be used, and what tolerances they can work to. A manufacturer should also be able to offer advice on related subjects such as the right screeds to use, how best to form a block-out for a recessed joint, and what fire barrier you need for a fire rated wall. A manufacturer’s knowledge can be a valuable resource that you can call upon during your project.
At Suzhou Omax Building Materials we are proud to say we offer:
More than 40 years experience with Expansion Joint Covers
Trained staff who know all there is to know about expansion joint covers and associated works
The most comprehensive range of covers in the world
Support at every stage of the selection process, right through to the technicalities of installation
An in-house installation team who can install any of our joints
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
sizing expansion joint coversOnce 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
expansion joint coversWill 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.
Omax have been manufacturing and installing expansion joint covers for more than 20 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.
There are several key criteria you must consider for expansion joint cover specification, but the following have the greatest impact on the selection process and are ranked accordingly:
1. Structural joint opening. This is nearly always established by the structural engineer and determines the size of cover needed.
2. Anticipated movement. Again, determined by the structural engineer and normally specified as plus or minus ‘x’ when ‘x’ may be a dimension, i.e. 10mm, or a percentage of joint opening i.e. 50%.
3. Type of building. The anticipated use of the building will help determine the type of cover system chosen. For example, a hospital will require covers that are easy to keep clean and also have a flush top surface since wheeled equipment is an aspect of normal building occupation. This would lead to the selection of a gasketed cover system. We recommend that the selection process start with the choice of floor cover as this is affected the most by such building usage. Wall covers are then simply matched to the chosen floor cover.CAUTION: rolling loads can have a significant impact on the function of a cover system. If heavy-wheeled equipment is expected, such as in airports, covers labeled “heavy duty” should be selected.
4. Aesthetic considerations. Once the above criteria are established, the final piece of the puzzle is appearance. Historically seismic joint covers have been known to ruin even the most carefully designed interior finishes scheme. Fortunately, CS has developed a complete range of covers with reveals that help conceal most of the cover plate regardless of the joints.