Expansion Joints Covers
What is an Expansion Joint?
In building construction, an expansion joint is a mid-structure separation designed to relieve stress on building materials caused by building movement induced by:
– thermal expansion and contraction caused by temperature changes,
– sway caused by wind,
– seismic events, etc.
Because the joint bisects the entire structure, it marks a gap through all building assemblies–walls, floors, roofs, decks, planters, plazas, etc. This gap must be filled to restore the waterproofing, fire proofing, sound proofing, air barrier, roof membrane, trafficable surface and other functions of the building elements it bisects.
Expansion joint systems are used to bridge the gap and restore building assembly functions while accommodating expected movements.
The term “movement joint” has been widely adopted in preference to “expansion joint” as it more appropriately encompasses the fact that building movement results in both compression and expansion of the material installed.
For example, when a structure heats up, the building materials from which it is built expand. This causes the “expansion joint” to close down, thereby compressing the expansion joint system installed in the gap.
Conversely, when the temperature drops, the materials cool causing the joint gap to open. This requires the expansion joint material to expand to follow the joint movement.
Joint Size vs. Movement Requirements:
The width of a movement joint and it’s movement requirements are not necessarily directly related. The joint size is simply the baseline width of the joint at its mean service temperature. (e.g., 2″) The movement requirements are how much the joint will increase &/or decrease from its baseline width (e.g., -1″ to +1″) due to project movement criteria. There are three primary movement criteria that are considered when determining joint movement requirements; thermal, deflection and seismic. If you have a 2″ joint size and the total joint movement requirements are -1″ to +1″, the joint has 2″ of total movement and is considered to have 100% movement at +/-50%. If you have a 4″ joint size with the same -1″ to +1″ movement requirements, the joint would be considered to have 50% movement at +/-25%. When detailing movement joint solutions it is critical to select movement joint solutions that can meet the movement requirements based on the joint size desired.
Screws and expansion anchors are commonly used to fasten rails, plates, and other systems offered for expansion joint sealing and bridging. By nature, screws are either self-tapping or require holes to be drilled and then the screws tapped into the holes. On brittle substrates like concrete, masonry or brick, drilling often results in spalling of the substrates and improper grip. Usually installed at an angle to the face of the joint substrate the act of screwing is often imprecise resulting in further substrate damage, shearing of the fasteners and loose attachment of the joint system. At inside corner applications common in additions or building plane changes, it is impossible to position a drill or driver to install anchors in the substrate opposite the inside corner. This often-overlooked condition results in the joint system being installed into an unreliable adhesive or not anchored at all.
|Parking & Exterior Expansion Joints|
|Fire Barrier Expansion Joints|
|Trench Grating & Access Covers|
Encore Building Products has decades long experience working with local and national expansion joint manufacturers, architects, specification writers,building owners, facility managers and engineers and specialty contractors and installers. Our involvement with not only the specifying and design community along with our hands on approach to assisting local contractors and a network of factory trained installers gives us the rare ability to solve complicated seismic expansion joint questions but also gives us the ability to work with our clients to find the best solution for their specific expansion joint application and challenge.
Encore Building Products takes a systems approach to solving difficult expansion joint problems and understands the complex nature of thermal and seismic building movement, moisture management as well as the unique nuances associated with many other trades including sheet metal, drywall, plastering, miscellaneous metals, roofing, waterproofing and concrete repair and restoration.
No other building product involves so many different trades and areas of compatibility than expansion joint systems.
Expansion Joint Use
An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of construction materials, to absorb vibration, to hold parts together, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of buildings, bridges, sidewalks, railway tracks, piping systems, ships, and other structures.
Building faces, concrete slabs, and pipelines expand and contract due to warming and cooling from seasonal variation, or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under the stress induced.
Expansion Joints are recommended to be provided for any one or more of the following minimum conditions.
When the floor plan size exceeds 200 feet in any direction
At all structural expansion or contraction joints
Where the deck material changes, for example from steel to concrete
Where the deck material or structural framing changes direction
Where building wings intersect, such as “U”, “T”, or “L” shapes
Where interior heating and cooling conditions change, such as between heated and unheated
At all building additions of any shape
Exterior Expansion Joint Covers can be made of aluminum, steel, stainless steel, brass, bronze, EPDM, neoprene, rubber, foam, silicone, saturated EPDM and sheet metal. Typical applications include parking structure drive aisles, elevator thresholds, pedestrian bridges and walkways, plaza decks and podiums, and exterior walls, roofs and soffits. A common characteristic of exterior expansion joint covers is its ability to manage or eliminate water intrusion into the structure.
Interior Expansion Joint Covers can be made of aluminum, steel, stainless steel, brass, bronze, EPDM, neoprene, rubber, foam, silicone, and sheet metal. Typical applications include walkways, corridors, elevator thresholds, pedestrian bridges and walkways, plaza decks , interior wall and ceilings. Interior expansion joint covers tend to be decorative in nature and can come in special finishes and colors.
Parking Structure Expansion joint covers and seals require heavier duty and thicker plates. In addition they are often designed to span greater joint openings and carrier heavier vehicular loads. Often these systems are required to incorporate secondary water containment systems and or/water seals.
Some expansion joint systems are designed to reduce sound and noise with the use of sound dampening spacers and rubber encapsulated plates.
On smaller joint openings (>5”) compression seals and inflatable joint seals are often used. These seals act as effective expansion joint covers as well as water containment seals.
Damaged or failing expansion joint systems can sometimes be repaired but it is usually more cost effective to remove and replace the entire system. Restoration work will often involve the repair and restoration of old and damaged concrete, moisture barriers and in some cases, fire blankets. As with new construction, there are interior and exterior restoration projects; each of which require careful assessment and inspection of existing joints, the building structure and the particular requirements of the project.
Some waterproofing expansion joint systems can be used without cover plates where as others need to be covered to comply with certain building codes and ADA requirements.
Inflatable seals, compressions seals and some pre-compressed foams can be used without the use of a cover plate whereas softer foam seals require a cover plate if pedestrian traffic is expected. Some expansion joint seals act as excellent waterproofing seals. Waterproofing expansion joint seals can be used across planter boxes, foundation walls, podium decks, walls, ceilings, roof decks, and plazas.
There are several options for roofing expansion joints; namely, sheet metal, rubber, silicone, aluminum, saturated EPDM and hybrid roof bellows which incorporate single-ply sheet membranes such as PVC and TPO.
Expansion Joint Roof covers should be designed as exterior expansion joint systems and consideration should be made to moisture and waterproofing.
Compression joints are typically used when lighter pedestrian traffic is expected or when water management is a requirement.
Inflatable joint seals are heavy duty neoprene seals that are installed with the use of an air compressor and adhesives.
Pre-compressed foams and seals offer design benefits and ease of installation for smaller vertical and horizontal applications. They also offer limited water-containment benefits.
Zotes are hardy closed cell foam materials that are UV stable and resistant to many chemicals and moisture. They offer excellent expansion and compression capabilities and are suitable for both interior and exterior applications where water is an issue.