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Rainscreen technology dates back to the Middle Ages, with examples seen in Norwegian churches that utilized panels with layers of open-jointed and back-ventilated claddings under wood or stone walls to allow for drainage. Since then, many technological advancements have been developed.
All images courtesy of Lamboo Technologies, LLC
Laminated bamboo panels were installed at the Western Reserve Distillery in Lakewood, Ohio, designed by Larsen Architects.
In the late 1960s, U.S. builders began using exterior insulation finish systems (EIFS), which are a general class of cladding systems that provide exterior walls with an insulated, water-resistant, finished surface. Unfortunately, this led to a rise in moisture-related damage to wall assemblies in EIFS-clad buildings. This resulted in an increase of lawsuits and subsequently encouraged the industry to look for solutions and ways to allow for secondary drainage.
Further advancements were made in the early 2000s with the development of a true rainscreen system that allowed for both ventilation and pressure equalization. Due to the success of this technology, not a lot has changed since then, but rainscreens have become increasingly popular in building envelope design in the United States. Laminated engineered bamboo, one of the newest additions to material choices available in rainscreen systems, provides added features in durability, moisture protection, sustainability, and contemporary aesthetics that most materials used in rainscreen systems today do not.
Protecting the Building from Air and Water Intrusion
Protection of the building envelope is vital to protecting the entire building against unwanted water and air intrusion. All materials in the building envelope must work together to ensure the building is both structurally sound and aesthetically pleasing. The building envelope consists of walls, floors, subfloors, exterior doors, windows, and the roof. It also includes all sealants and fasteners that bind the materials together.
Water is a unique opponent, as it is a fluid that can be forced into tiny cracks and unsealed joints, especially when forced against building walls and soffits by strong winds in hurricanes and blizzards. If moisture from humidity, rain, ice, or snow penetrate the envelope, over time, it can cause mold, mildew, and rot. This can lead to costly repairs and renovations.
Ideally, all exterior surfaces of a building would be airtight, but that is a difficult feat. Over time, temperature changes can cause expansions and contractions in a building, resulting in cracks in drywall, plaster, and cement walls. They can also create cracks in sealants around penetration points.
When specifying materials and design choices to prevent air and water intrusion, architects and designers try and address the “4 Ds” of water management: deflection, drainage, drying, and durability. Engineered bamboo rainscreens address all four Ds, thus protecting the building from costly and destructive water damage.
Deflection
Cladding or window head flashings will direct and deflect water (such as rain or snowmelt) from the building’s exterior. They will also keep water away from vulnerable junctions where moisture could enter the wall system. Roof eaves are one example of how rainwater can be deflected away from the walls.
Drainage
Drainage is also important within a wall system so that any water that is not deflected can drain down the back of the wall cladding and out of the full wall assembly.
Drying
Rainscreens help with this by providing an air cavity between the cladding and the exterior substructure. These air gaps also help keep the wall system dry by circulating the air inside the system.
Durability
Rainscreen technology provides the initial layer of defense against driving rain, moisture, and even wind. This allows the building to be shielded from the initial forces that are applied against the system, providing a better overall performance of the building envelope where the system is installed.
Since most rainscreen systems are back ventilated, this allows the actual materials used in the rainscreen system to perform better and be more durable against harsh weather due to any water that makes it past the initial layer of rainscreen to simply drain behind the system and not become trapped. This is where most issues such as mold, decay, and rot with traditional siding and direct fastened siding occurs.
Due to the inherent properties of bamboo, engineered laminated bamboo rainscreens not only provide protection against unwanted moisture intrusion (even from driving rain) but are also naturally nonconductive and thus provide additional thermal protection. Architects can rely on engineered laminated bamboo to provide longer spans and better overall performance compared to other traditional building products. Engineered laminated bamboo also enhances the aesthetics of the exterior facade.
Anatomy of a Rainscreen
The term rainscreen is sometimes thought to refer to the siding itself, while other times it implies a complete building system. The rainscreen system works together to control air and moisture intrusion by creating a barrier between itself and the sheathing to help minimize the amount of moisture that may collect on the sheathing. These systems also often provide equal pressure on both sides of the rainscreen and are typically comprised of an outer cladding, a cavity, and an air and vapor barrier or water-resistive barrier (WRB).
Rainscreens are made up of an outer cladding, a cavity, and an air and vapor barrier or water-resistive barrier (WRB).
Outer Cladding
The outer cladding is the primary barrier to water intrusion. Some refer to this as the “rainscreen.” However, the rainscreen system is not fully effective without the other components. The outer cladding is the first line of defense and designed to deflect or shed away the majority of the water that hits the building’s surface. This tough exterior must be made from a material that can withstand extreme weather such as driving rain, snow, and ice. In dry conditions, the outer cladding can also protect the building’s inner wall and the inner workings of the rainscreen against ultraviolet (UV) rays. The engineered joints between the panels allow for ventilation, which is critical to overall performance of the cladding.
Rainscreen technology dates back to the Middle Ages, with examples seen in Norwegian churches that utilized panels with layers of open-jointed and back-ventilated claddings under wood or stone walls to allow for drainage. Since then, many technological advancements have been developed.
All images courtesy of Lamboo Technologies, LLC
Laminated bamboo panels were installed at the Western Reserve Distillery in Lakewood, Ohio, designed by Larsen Architects.
In the late 1960s, U.S. builders began using exterior insulation finish systems (EIFS), which are a general class of cladding systems that provide exterior walls with an insulated, water-resistant, finished surface. Unfortunately, this led to a rise in moisture-related damage to wall assemblies in EIFS-clad buildings. This resulted in an increase of lawsuits and subsequently encouraged the industry to look for solutions and ways to allow for secondary drainage.
Further advancements were made in the early 2000s with the development of a true rainscreen system that allowed for both ventilation and pressure equalization. Due to the success of this technology, not a lot has changed since then, but rainscreens have become increasingly popular in building envelope design in the United States. Laminated engineered bamboo, one of the newest additions to material choices available in rainscreen systems, provides added features in durability, moisture protection, sustainability, and contemporary aesthetics that most materials used in rainscreen systems today do not.
Protecting the Building from Air and Water Intrusion
Protection of the building envelope is vital to protecting the entire building against unwanted water and air intrusion. All materials in the building envelope must work together to ensure the building is both structurally sound and aesthetically pleasing. The building envelope consists of walls, floors, subfloors, exterior doors, windows, and the roof. It also includes all sealants and fasteners that bind the materials together.
Water is a unique opponent, as it is a fluid that can be forced into tiny cracks and unsealed joints, especially when forced against building walls and soffits by strong winds in hurricanes and blizzards. If moisture from humidity, rain, ice, or snow penetrate the envelope, over time, it can cause mold, mildew, and rot. This can lead to costly repairs and renovations.
Ideally, all exterior surfaces of a building would be airtight, but that is a difficult feat. Over time, temperature changes can cause expansions and contractions in a building, resulting in cracks in drywall, plaster, and cement walls. They can also create cracks in sealants around penetration points.
When specifying materials and design choices to prevent air and water intrusion, architects and designers try and address the “4 Ds” of water management: deflection, drainage, drying, and durability. Engineered bamboo rainscreens address all four Ds, thus protecting the building from costly and destructive water damage.
Deflection
Cladding or window head flashings will direct and deflect water (such as rain or snowmelt) from the building’s exterior. They will also keep water away from vulnerable junctions where moisture could enter the wall system. Roof eaves are one example of how rainwater can be deflected away from the walls.
Drainage
Drainage is also important within a wall system so that any water that is not deflected can drain down the back of the wall cladding and out of the full wall assembly.
Drying
Rainscreens help with this by providing an air cavity between the cladding and the exterior substructure. These air gaps also help keep the wall system dry by circulating the air inside the system.
Durability
Rainscreen technology provides the initial layer of defense against driving rain, moisture, and even wind. This allows the building to be shielded from the initial forces that are applied against the system, providing a better overall performance of the building envelope where the system is installed.
Since most rainscreen systems are back ventilated, this allows the actual materials used in the rainscreen system to perform better and be more durable against harsh weather due to any water that makes it past the initial layer of rainscreen to simply drain behind the system and not become trapped. This is where most issues such as mold, decay, and rot with traditional siding and direct fastened siding occurs.
Due to the inherent properties of bamboo, engineered laminated bamboo rainscreens not only provide protection against unwanted moisture intrusion (even from driving rain) but are also naturally nonconductive and thus provide additional thermal protection. Architects can rely on engineered laminated bamboo to provide longer spans and better overall performance compared to other traditional building products. Engineered laminated bamboo also enhances the aesthetics of the exterior facade.
Anatomy of a Rainscreen
The term rainscreen is sometimes thought to refer to the siding itself, while other times it implies a complete building system. The rainscreen system works together to control air and moisture intrusion by creating a barrier between itself and the sheathing to help minimize the amount of moisture that may collect on the sheathing. These systems also often provide equal pressure on both sides of the rainscreen and are typically comprised of an outer cladding, a cavity, and an air and vapor barrier or water-resistive barrier (WRB).
Rainscreens are made up of an outer cladding, a cavity, and an air and vapor barrier or water-resistive barrier (WRB).
Outer Cladding
The outer cladding is the primary barrier to water intrusion. Some refer to this as the “rainscreen.” However, the rainscreen system is not fully effective without the other components. The outer cladding is the first line of defense and designed to deflect or shed away the majority of the water that hits the building’s surface. This tough exterior must be made from a material that can withstand extreme weather such as driving rain, snow, and ice. In dry conditions, the outer cladding can also protect the building’s inner wall and the inner workings of the rainscreen against ultraviolet (UV) rays. The engineered joints between the panels allow for ventilation, which is critical to overall performance of the cladding.
Cavity
The cavity is the well-ventilated area between the outer cladding and the wall behind it. The cavity is essential to the integrity of the rainscreen, as it helps to vent vapors to the outside and wicks away moisture from the sheathing’s surface. The ventilation in the cavity helps keep it dry, thus keeping the inner wall protected from water damage. The cavity must be a minimum of 3⁄8 inch (1 centimeter) deep, but ideally will be closer to 2 inches (5 centimeters) to properly allow the water to escape and the air to circulate. To further protect the cavity, it is important to install continuous roof flashing to prevent water and air from seeping into the cavity from the roof.
Air and Vapor Barrier
The air and vapor barrier is the final layer that protects the building walls from moisture. This final layer could be a variety of materials, including but not limited to cement, WRBs, or exterior sheathing. Regardless of the material type, it should be properly sealed.
Types of Rainscreens and How They Protect the Building Envelope
Essentially, there are three types of rainscreens available: vented systems, drained and vented systems, and pressure-equalized systems.
Vented
Vented systems are only open at the bottom and utilize a warm cavity that provides a dew point similar to the dew point outside, which in turn reduces the change of moisture entering the system. This system type is not recommended for buildings more than four stories high.
Drained and Vented Systems
Drained and vented systems are not watertight and require a cavity opening at both the top and bottom to provide drainage and promote convection ventilation. Typically, an overhang is used to protect the cavity from the elements. This system is also not recommended for use in buildings more than four stories high to prevent a buildup of condensation.
Pressure-Equalized Systems
Pressure-equalized systems allow for ventilation openings large enough to equalize pressure on both sides of the cladding. A lot of attention must be taken to design the system so that there is a balance between the amount of air flowing into and out from behind the rainscreen panels.
The American Architectural Manufacturers Association (AAMA) recognizes two basic types of rainscreen systems, grouping the vented and drained and vented systems into a single category (drained, back ventilated) and pressure equalized/pressure moderated into a second category.
The AAMA provides voluntary system tests for drained, back-ventilated systems (AAMA 509-09) and pressure-equalized/pressure-moderated systems (AAMA 508-07).
The Effectiveness of a Complete System
All of these systems are designed on the idea that water does not move on its own. Rain, snow, and sleet are moved downward by gravity or sideways by wind. The outer cladding breaks the force of the downward or sideways driven moisture, which means any water that makes its way through that barrier has lost its momentum. Any water that gets through that first layer of outer cladding is no longer driven by an exterior force of wind and is only seeping by the time it reaches the cavity. In the cavity, gravity takes over and water runs down the inner side of the cladding, not touching the rest of the wall. If any moisture does touch the inside of the wall, it will touch the air and vapor barrier that provides an added layer of protection against the inner wall.
It is important that there is a place at the bottom of the wall for water to exit or drain out of the cavity. Using proper sealants to provide a waterproof barrier around any potential penetrations, such as fasteners, is also key. Some rainscreen applications have an opening at the top and bottom of the cladding to allow for airflow and ventilation throughout the cavity to quickly dry out the space after a weather event.
Drained and back-ventilated systems that are well designed and tested can stop more than 90 percent of the water that could potentially reach the air and vapor barrier of the building. The combined action of gravity through the drainage and evaporation through air circulation will take care of the remaining 10 percent of water that makes it into the rainscreen system, thus protecting the building structure.
Add-ons for Additional Protection and Aesthetics
To ensure the rainscreen system works as efficiently as possible, additional features such as engineered corners, siding vents, and window/door trims can be included in the assembly.
Laminated engineered bamboo window and door trims not only provide an aesthetically pleasing facade, but they can also protect these openings against moisture intrusion from driving rain and snow.
These add-ons not only provide additional protection for the building envelope, but they also enhance the aesthetics of the building. A variety of colors and finishes are available, allowing architects and designers to get the desired look and feel. Color and grain patterns are utilized to mimic real wood and will promote variations in finished color due to the various angles and impression depths left by embossing the materials. All add-ons can be finished to match the other panels.
Laminated engineered bamboo outside corners, window, and door trim add-ons allow designers and architects to properly seal the building envelope without compromising aesthetics.
Understanding the Benefits of Bamboo Compared to Other Materials
When selecting building envelope materials, such as rainscreens, trim, and corner covers, the materials need to be appropriate to the climate. There are many material options available, including wood, steel, aluminum, and plastic.
While metal is largely resilient to water intrusion, areas where the panels meet can become vulnerable. Sealants placed at the junctions can deteriorate due to age, sun exposure, and drastic temperature changes. Wood panels must also be sealed to one another to provide a waterproof barrier and are prone to splitting and cracking due to age and weathering. Plastic can provide protection against water intrusion, but it is not a renewable resource.
In recent years, engineered bamboo has become a popular type of building material for many reasons. These new bamboo products are engineered for uniformity, consistency, and typical construction tolerances so they can be used just as readily as steel, aluminum, or plastic components in multiple applications, including interiors, exteriors, and structural applications. In some cases, as outlined in this course, there are advantages to using bio-based materials over metals and other structural systems.
When compared to plastics, aluminum, or steel, bamboo is a renewable and sustainable resource that does not create as much waste in the landfill as a majority of the waste produced is utilized within other engineered bamboo products. When compared to wood, bamboo provides added benefits in that it requires low maintenance and is more dimensionally stable. Maintenance of engineered bamboo is very similar to wood, but its ability to stay dimensionally stable in exterior applications aids with the overall performance of stains and coatings used on the bamboo. Engineered laminated bamboo’s antimicrobial properties are also seen as a benefit since the resulting products limits moisture buildup, thus preventing mold and mildew from damaging the building or causing harm to occupants in wet or damp climates. Silica content within the material acts as a natural insect and termite deterrent as well.
Since engineered laminated bamboo can be used in a variety of applications, each material type will come with a manufacturer warranty. However, some materials will have better warranties than others due to their durability and tolerances. When selecting a material, be sure to compare warranties when weighing other factors such as initial cost. In most cases, engineered laminated bamboo warranties are equal or greater than competitive products, such as exotic hardwoods or other engineered building products.
Rapidly Renewable Resource
Bamboo is one of the most rapidly renewable resources on the planet. It is best harvested when it reaches its maturity in four to five years after initial planting. When it is harvested, the stem is left in the soil to sprout a new shoot and restart the growing process. This is a significant advantage over timber and exotic hardwood production, as they will need to have the entire tree removed and then the ground is reworked to replant another tree. Bamboo also thrives in depleted soil, which means it can be grown in areas where forests have been clear cut or burned. It is also one of the few plants that not only grows easily but can also return nutrients to the soil and reduce soil erosion. Bamboo also grows in areas where other softwoods or hardwoods would have difficulty in growing due to over saturation and unfavorable soil conditions.
Essentially bamboo is a giant grass, comprised of a hollow, tapering culm (stalk) of longitudinally oriented fibers divided by nodes. From the interior to the exterior, the bamboo fibers increase in density. These fibers are essential to creating structural-grade engineered bamboo.
Engineered for Durability
While bamboo is already dense and durable on its own, technological advancements have helped make bamboo an even more reliable rainscreen product. Behind the scenes, manufacturers are discovering ways to boost the performance of engineered bamboo to achieve greater sustainability as well as improved durability, uniformity, and strength. One manufacturing method produces strand-woven or parallel-strand bamboo, made from crushed fiber bundles soaked in resin and treated under pressure to create solid, dense slabs. A second method, known as laminated bamboo, also maintains the longitudinal fibers as the parallel-strand process does, but it also takes advantage of the natural culm matrix. The bamboo stalks are cut and planed, and then processed as desired prior to the lamination and compression in board form. This process typically utilizes less adhesive and tends to provide higher strength-to-weight values.
This means that architects and end users can rely on structural engineered bamboo for longer spans, larger loads, and more extreme conditions. Facilitating these advancements are manufacturing enhancements to make stronger and more durable glulam beams and common dimensional components, as well as hybrid structural solutions and complete systems.
In addition, today’s manufacturers of laminated engineered bamboo panels offer consulting, shop drawings, detailed structural system analysis, engineering, custom three-part specifications, fabrication, and installation advice as needed for their projects. This ensures that designers and architects can specify the right product for the right job.
The strength and efficiency of laminated engineered bamboo, along with the positive carbon footprint of rapidly renewable bamboo, make it a suitable choice for high-performance buildings. The products are also engineered for a high degree of uniformity and consistency, ensuring tolerances within those required for building enclosures and structures.
One of the many benefits is that the engineered bamboo materials have tested to be more stable in climate and temperature changes than engineered woods. Laminated engineered bamboo materials present better mechanical properties over typical natural wood materials, which means they are ideal for window and door products and assemblies. Laminated engineered bamboo functions similarly to hardwoods; however, it has a much better dimensional stability and as a building product can be more sustainably sourced.
Green Building Construction
Not only does the natural product grow quickly, but it is also biodegradable and limits the amount of waste going into the landfill, especially when compared to other building materials such as plastic, aluminum, and stainless steel. Because they are sustainable, strong, and durable, engineered bamboo panels, as well as laminated veneer bamboo materials, are increasingly used for building exteriors and as exposed, load-bearing members. For sustainable buildings and LEED-certified projects, engineered bamboo panels are used for facades, cladding, curtain walls, structural glazing, as well as a range of window and door solutions.
A rainscreen system utilizing laminated engineered bamboo offers more LEED credits than those that use exotic hardwoods and local natural products like cedar and pine. With increased use of engineered bamboo, building projects may qualify for several credits toward LEED v.4 certification, including:
- EAc2: Optimize Energy Performance
- MRc3: Sourcing of Raw Materials
- MRc4: Material Ingredients
- EQc2: Low-Emitting Materials
- Inc1: Innovation
Thermal Protection
In addition to providing protection against unwanted air and water intrusion, bamboo is also naturally nonconductive and therefore helps reduce thermal transfer. The conductivity of the bamboo is related to its density. Since engineered bamboo is at a higher density than many equivalent timber products, bamboo can help a building use less energy because thermal energy is not as easily transferred through the engineered bamboo panels. Along with bamboo’s resistance to thermal conductivity, this makes engineered laminated bamboo a material of choice with rainscreen systems. By creating a gap between the exterior wall and the bamboo in a rainscreen system, this helps keep the air temperature behind the rainscreen cooler, which provides overall cost savings in cooling buildings during the summer time heat. This further adds to bamboo’s list of environmental qualities, as energy use and costs will be lower in buildings with laminated engineered bamboo panels.
Considerations Before Installing Laminated Engineered Bamboo Rainscreens
After determining that engineered bamboo panels or laminated bamboo rainscreens are right for your application, it is time to begin the installation process. Another major benefit of engineered bamboo panels and laminated bamboo dimensional components is that they are available in various sizes and lengths to accommodate project requirements. For panels, typical-size panels are 4 feet wide x 8 feet long and available in 1⁄2-inch and 3⁄4-inch thicknesses. For dimensional components, they are available in lengths up to 20 feet and as wide as 12 inches. Single panels can cover large swatches of the building without needing to be cut.
Some bamboo rainscreen systems also utilize an attachment system that is easy to install and reduces extended installation times and cost, unlike other systems that utilize facade applications. Installing exterior laminated engineered bamboo rainscreens is so easy that occupants can remain inside while panels are being installed.
This section will provide a high-level overview of installation best practices for laminated bamboo rainscreens, including storage guidelines, do’s and don’ts, guidance for the type of fasteners to use, care and maintenance, and an overview of the installation steps.
Installation Do’s and Don’ts
When working with laminated bamboo panels or dimensional components, there are some general guidelines to follow.
Do’s
- Use sharp tool bits and blades when making cuts into laminated bamboo wall cladding or other parts of the wall cladding substructure. This will help minimize any “tear-out” to the panels when cutting.
- Pre-drill holds for direct fastening into the wall cladding prior to installing the fastener.
- Keep wall cladding surfaces clear of unnecessary clutter and buildup of waste and drop materials. If not handled correctly, unused or scrap wall cladding boards could damage installed wall cladding surfaces.
- Fasten the wall cladding according to the manufacturer’s installation guidelines. This will help minimize issues due to expansion and contraction.
- Keep wall cladding products stored in cool areas prior to installation. Wall cladding exposure to direct sunlight prior to installation may cause the materials to build up heat and expand, causing the boards to lengthen.
Don’ts
- Avoid wearing loose clothing when using tools that spin at high RPMs to cut or install laminated bamboo panels.
- Do not allow dust from concrete, landscape blocks, rock, or other masonry products to accumulate on the wall cladding surface. If any dust should occur, it should be cleaned immediately. Failure to do so can cause surface staining.
- Do not mount directly to concrete. A sleeper should be used with a minimum height of ½ inch. The sleeper should be mounted to the concrete with the appropriate fasteners where the wall cladding product will be mounted to the sleepers either by face fastening or using the hidden clip system.
- Do not install where low-emissivity (low-e) glass is used. Low-e glass is designed to prevent heat gain within a structure and can cause unusual heat buildup on exterior surfaces. Excessive heat buildup greater than normal exposure limits could potentially cause several issues, such as sagging, bowing, warping, discoloration, excessive expansion/contraction, and accelerated weathering.
Fasteners
When choosing fasteners, it is recommended that high-quality fasteners be selected based on the following specifications. Be sure to use stainless steel screws with a minimum screw size of #10. Face-fastening screws should have a minimum length of 2 inches. Fasteners should drive at least 3⁄4 inch to 1 inch into the solid framing behind the wall cladding.
Avoid using flathead screws. Trim-head screws typically provide better results. Always sample the type of fastener in a scrap piece of wall cladding prior to using for final installation. For installation jobs near coastal areas with a high salt content in the air, be sure to use stainless steel fasteners with a minimum alloy of 316 stainless steel.
Storage of Material Prior to Installation
Prior to installing laminated engineered bamboo rainscreens, ensure that all products are stored on flat, level surfaces. It is also important that materials are stored in cool, shady areas away from direct sunlight. Ensure that the storage area temperature does not exceed 120 degrees Fahrenheit. Do not stack in bundles over four units high, and be sure to leave the factory-applied protective wrap on the sheets until it is time to install. If materials are to be stored outside, cover with a non-translucent material. Use care when handling materials with forklifts, lulls, skid steers, and other material handling equipment.
Installation of Laminated Engineered Bamboo Wall Cladding
While these panels are supplied prefinished and designed for easy installation, it is important to consult the manufacturer before making any adjustments or alterations to the panels before installation. This section will outline best practices and guidelines for installing clip horizontal engineered laminated bamboo outer wall cladding. However, before installing the panels, be sure to follow the manufacturer’s guidelines fully to prevent voiding any warranties. While some of the fundamental concepts may be similar, installation of other engineered laminated bamboo products will have separate instructions that should be consulted and followed.
Prior to installation, proper acclimation is imperative. Before starting any exterior installation, always make sure your material has properly acclimated to local site conditions. If the materials are not properly acclimated for 24–48 hours prior to installation, it could result in poor or undesired results.
Pre-check List Before Installation
Prior to installation, confirm that these important steps have been done properly.
Pre-Check 1: Ensure your structural sheathing has been attached properly to the framed wall system per manufacturer’s instructions and local building codes. Plywood or oriented strand board (OSB) may be used. The panel thickness should be rated for structural application and must be a minimum of 7⁄16 inch thick. Plywood is typically stiffer and stronger than OSB. Thicker plywood or OSB makes a stronger wall and has greater holding strength of the screw. Foam and gypsum boards are not structural panels.
Pre-Check 2: Make sure the drainage plane material has been properly installed. Use the appropriate air and vapor barrier or WRB as specified by the architect or designer. There are many products available to address requirements of the exterior wall in the climate zone where the panels are being installed.
Pre-Check 3: All windows and exterior doors should be installed properly before starting installation of the rainscreen panels. Check to ensure that the installation (and flashing) instructions from the door and window manufacturers were properly followed. Window and door manufacturers’ installation instructions always take precedent over these guidelines.
Installation Process for Horizontal Laminated Engineered Bamboo Rainscreens
Step 1: Ensure all siding boards are pre-finished prior to assembly. This is the only way to ensure that all four sides are coated evenly. It is highly recommended to coat all siding with a UV-inhibiting sealer prior to installation. A UV-inhibiting sealer helps the rainscreens to acclimate more slowly and minimizes surface checking and movement. The manufacturer typically provides prefinished panels, but some installers may choose to add finishes at the site. If done at the site, ensure all surfaces (edges, faces, slots) are properly coated. Follow the stain supplier’s surface prep and coating recommendations.
Step 2: Create a level line for the starter rail on the wall. This can be done with a laser level or snapped chalk line. It is recommend that you complete this on all walls first to ensure the starter rail level line will be consistent on all sides of the building. This step is critical to a successful siding installation and should be done with accuracy. The level line should be positioned approximately 1½ inches above the bottom of the sheathing or 1½ inches above the top of the foundation sill.
Take your time is performing this step well, and all the next rows of siding will be properly aligned.
This is an example of chalk line placement at the bottom of a wall. This is where the beginning of the system starts with the installation of the starter rail. It is important to take extra care with this step to ensure proper installation.
Step 3: Install selected engineered corners (optional). If engineered outside corners were specified, install those now. Stainless steel fasteners must be used to fasten the engineered corners to the sheathing. Refer to the manufacturer’s installation guidelines in order for proper fastener spacing.
Optional engineered corners can better seal the building envelope while also providing an aesthetically pleasing facade.
Step 4: Install the window and door trim. Install all window and door trim and put proper flashing in place. Always follow the window and door manufacturers’ installation and flashing instructions.
Step 5: Install the starter rail. To speed up your installation and help provide the critical level line to start your horizontal siding installation, use a starter rail. This provides a continuous strip at your bottom course of siding. Many starter rails are provided between 8 feet and 12 feet in length, and they have pre-drilled holes for mounting to the plywood walls and weep holes on the bottom of the rail to allow water drainage.
Step 6: Install the siding vent. It is recommended to install a siding vent system to prevent insects from entering the wall cavity from the ground and allow for proper drainage of water that may penetrate behind the rainscreen system. The siding vent system fills the rainscreen wall cavity between the drainage plane created by the mounting clips. It is also suggested to install the siding vent at the soffit, above door openings, and above/below window openings.
Step 7: Insert the bottom start piece of the laminated engineered bamboo rainscreen siding board into the starter rail. Place the bottom groove of the laminated engineered bamboo material into the starter rail lip. Use a rubber mallet as needed to seat the board properly into the clip. Seating each board properly gives the best alignment for your wall.
If your board does not seat properly, do not install it. Never “force” a board into place. It may cut, bend, or bow the board or other boards around it voiding the warranty.
Attach the rainscreen clips to the top of the siding board. Space the rainscreen clips at 16 inches to 20 inches on center using one screw per clip. For shorter runs, add an extra clip anywhere needed. The more clips you use, the better the board will behave over time.
The first laminated engineered bamboo rainscreen has been inserted into the starter rail and installed.
Step 8: Repeat the clip installation process for each row of siding. A major benefit of this system is that the installer can use full length siding boards. Simply use a rainscreen clip at the bottom and top of the joint and straddle the two boards anywhere a joint the length of the siding is needed. Always use two clips to secure the ends of siding boards. When butting two siding boards together, it is a best practice to use the “scarf joint” technique.
A 45-degree angle at each end of cut boards work best. Master craftsmen prefer this method for best results and a quality installation you will be proud of for years. (If you use standard butt joints with 90-degree cuts, over time, the joints may open with weather exposure.)
Step 9: Install the top row of siding. When you reach the soffit (or areas below window openings), it is often necessary to rip the top of the siding to the appropriate width.
The bottom edge of the top row of siding will seat in the rainscreen clip. The top edge of the siding will need to be drilled and face screwed to blocking behind the siding.
Care and Maintenance
Proper care and maintenance are vital to ensuring a long life for your laminated engineered bamboo panels. For exterior applications, be sure to clean off any chemicals, such as lawn-care chemicals, insect repellent, or other chemicals that may come into contact with the wall cladding materials immediately to avoid any chemical reactions or discoloration with the stain or finish. When selecting cleaning materials, you can use typical cleaners found in the market for composite materials. Wall cladding materials can be easily cleaned with the use of a power washer set to the lowest setting (less than 1,200 psi), and the user must start at least 18 to 24 inches away from the wall. Before using any cleaner on the panels, it is recommended to test cleaners and power washing strength on scrap materials prior to using on finished products.
Conclusion
Laminated engineered bamboo rainscreens are not only made from a renewable resource that provide better air, moisture, and thermal protection, but they also provide a multitude of performance, sustainable, and aesthetically pleasing features to a building facade.
