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Bending Wood Handrail
Bending wood handrail is easily understood and can be accomplished by a novice who has some woodworking experience. If your experience in woodworking is advanced, this is a easy process and can be a very rewarding experience.
Preparation - Despite the fact that this illustration in this guide shows the handrail being bent on finished treads, it is always best to bend the rail on the rough framing rather than the finished treads so you do not have to worry about damaging expensive finished tread material. The handrail can be bent and the treads installed after the clamps have been removed and bending process completed. Proper planning for the location of the balusters, newel posts, and fittings is critical in any stairway installation, thinking ahead and planning where all your components will be placed will make the job proceed with ease.
Handrail - First of all, wood bending rail is manufactured from thin, vertical strips of wood that resemble the profile of the handrail when placed together. The strips have a keyway (tongue and groove)in the center to make sure that they align properly when glued together to maintain the handrail profile. Additionally, all bending handrail comes with a bending mold to protect the handrail when clamping the handrail together.
Handrail should never be bent in a radius tighter than 48". Before attempting to install any bending handrail, it is important to understand that the stair run and rise must be consistent throughout the stairway to prevent any kinks in the handrail that would appear unsightly and irregular. Always order an additional 2 to 4 feet of bending rail for excess at the top and bottom of the run to allow for the proper cutting of the final fitting of the joints.
Handrail Positioning - Proper placement of the handrail on the steps is crucial to proper alignment of the balusters within the center line of the rail. Determine the centerline of the balusters on the steps, always take into consideration the placement of the newel posts, volutes, and handrail fittings when positioning the balusters on the steps. Measure the overall width of the handrail, including the bending mold, divide this measurement in 2 and this will be the centerline of the handrail. We will use this measurement later in the installation instructions.
Next, mark the centerline of the balusters on the steps. Always allow for enough room on the actual tread to make sure that the holes drilled to accept the balusters will fall inside the edge of the outer skirt boards. Being to close to the edge will present problems later down the road. I would recommend that the balusters be centered at least 3" from the edge of the stair tread, if the stair tread has a 1" overhang on the skirt board, this will place your baluster hole 2" inside the edge of the skirt board.
Bending Guides - You will now need to fasten bending guides to the stair treads. Bending guides are L-shaped brackets made from wood or iron and designed to allow and withstand the tension and stress caused when the rail is forced in the guide and clamped together.
The bending guides shown above are made from 2x4 material with plywood gussets screwed and glued to both sides for strength. Most bending guides can be used several times over a number of installations if necessary. Professional installers also use metal bending guides made from welded angle iron or tubular iron, these last longer but are more expensive and only necessary if you plan on bending many lengths of handrail over time. Bending guides can be fastened to the steps by clamping them in place or screwing them to the treads. You can only use screws if the tread material is rough framing, you should never place screws directly in the finished tread material. Handrail can be bent prior to installing the finished tread material, this is usually easier because you do not have to worry about any damage to the finished material, including the glue from the bend mold.
Bending Guide Placement - Previously, you determined the proper placement of the handrail in relation to balusters and newel posts on the treads, this mark was made on the treads which is the centerline of your balusters and handrail. Next, you measured the overall width of the handrail, in the illustration above, the overall width of the handrail, including the bending mold is 2-3/4", so the center, from this example would be 1-3/8". You would now place a mark on each of the bending guide 1-3/8" from the edge, this mark will then be aligned with the mark on the step (or treads), and the clamps or screws are installed to hold the guides firmly in place. Please note: the illustration below has cardboard on top of the treads as protection, as stated earlier, it is not recommended that the finished treads be installed prior to bending the rail. Also note: All handrail varies in width and all centerlines differ from stairway to stairway, the measurements given above are simply an example used in these instructions, actual measurements will vary.
"Springback" is a term commonly used in bending handrail. It is the expansion of the bent rail when removed from the guides after gluing and clamping. This is very hard to predict if any springback will occur in a particular job site application, factors include the type of wood, handrail profile and radius. Most installers bend the rail as described and the springback is adjusted in the final baluster placement. Many typical stairway installations involve 13 treads, and most installers expect there to be approximately 3/8" in rail springback, if this is of concern, adjust the bending guides accordingly to account for this movement. This 3/8" springback is not commonly a concern, when the final balusters are installed, this difference is not noticeable but if it is of concern, make the proper adjustments.
Align the bending guides to the front of each tread. Again, please take precautionary measures with cardboard to prevent from damaging the steps from clamping and adhesive "squeeze out" when pressure is applied to the clamps. Again, it is recommended that the bending of any rail be done on rough treads rather than finished treads.
Bending guides should also be positioned in a manner to pull the rail rather than push the rail into the guide. When you begin clamping the glued rail at the top, you apply the first clamp to the guide, pull the rail into the next guide, apply a clamp and continue this procedure until the rail is bent and all clamps are applied. As stated, leverage is greater by pulling the rail into the guides rather than pushing it into the guides.
When all the guides are installed, one on each tread, the form is now ready to accept the bending rail.
Preparing the Bending Rail - Care must be taken to prevent any adhesive from adhering the bending mold to the handrail. Most installer place a small piece a plastic sheathing between the bending mold and the handrail, this plastic is approximately 16" wide bu the length of the rail. Cut to sections of this plastic, one for each side of the bending rail, this will give you plenty of extra and can finally be wrapped around the rail to catch the glue "squeeze out".
Next, you will lay all your pieces of bending rail on a work surface in the proper order. Keep in mind that each piece of bending rail has a specific position in the process: 1. the LH outside bend mold; 2. the LH outside rail profile; 3, 4, 5, 6, 7. the intermediate rail pieces; 8. the RH rail profile; 9, the RH outside bend mold. All pieces must go into the form and be glued in the proper order to maintain the proper profile of the handrail.
Begin by preparing a work surface such as sawhorses and the lay piece #1 (the bend mold) on its back and place the plastic on the bend mold as described earlier. This will prevent you from adhering the bend mold to the handrail. Next lay piece #2 through 8 in the order that they will be placed together to form the handrail, and finally lay the #9 RH bend mold on the far side, again, with the plastic to prevent adhesion to the handrail.
Adhesive - It is critical that you choose an adhesive that is designed for this type of application with extended working time. Most handrails are 7 ply and as many as 9 plys, coating each of the plys with adhesive and putting them in the proper order and then placing the entire handrail system in the bend mold and clamping takes times. Use and adhesive that give you enough time to complete tis process. Coating the plys, putting them together, placing the system in the mold and clamping, will take anywhere from 20 to 40 minutes. In addition, you will need extra help for this process, usually 3 people are necessary. It is best to place the adhesive in a small container and apply it with a brush or even a roller depending on your preference.
Liberally apply adhesive to ply #2 and place this on the plastic coated bend mold. Apply adhesive to both sides of ply's 3-7 while placing them in the proper order in the handrail configuration. Apply adhesive to ply #8, placing it in the final position. Finish the process by placing the plastic over the handrail and then the last section of bend mole. It is critical that you coat all the plys on both sides with adhesive to prevent failure, a dry pocket in the handrail will cause problems. The additional adhesive will be squeezed out of the handrail when pressure is applied with the clamps, this is normal and the adhesive will dry and later be scraped and sanded.
Clamping the Handrail - The next step is to take the glued handrail section to the bending guides and begin putting it in place and clamping the handrail. You can start at the top bending guide or the bottom bending guide, whichever allows you to work the handrail and pull it into the guides. Make sure the end of the bending rail, both top and bottom extend beyond the first and last bending guides for enough finished rail to be cut for final fitting.
Clamp the first handrail section to the bending guide, make sure the rail is flush to the bottom of the guide throughout the entire process, pull the rail into the next guide, apply a clamp, and so on until all clamps have been applied. While pulling the handrail into the clamps, always make sure the handrail is parallel to the stair treads and straight for proper alignment to the newel and fittings. Return to the first clamp applied and check the tension of the clamp and all other clamps to make sure the tension has not loosened.
Additional clamps need to be placed between all the clamps on the bending guides directly on the handrail. This will insure that even pressure is applied throughout the handrail and provide adequate and consistent adhesion. Place at least one clamp between each of the bending guides from top to bottom. Once again, re-check all clamps top make sure that the tension is tight.
The final step in thr process is to properly align the top and bottom rail that extends beyond the bending guides. Determine the proper alignment and if necessary, put a brace against the rail to move it into the proper position while the adhesion is curing.
After sufficient drying time, at least 24 hours, you can check the handrail to make sure it is completly cured. Loosen one clamp and closely examine the handrail at this position, the joint should stay completely closed. In some case, high humidity, extreme temperatures, the clamping may need to be longer than 24 hours. Always check the manufacturers recommendations on adhesion curing.
Remove the clamps and remove the handrail from the bending guides. Scrape the excess adhesive off the handrail. Sand the handrail with a belt sander or orbital sander. Always be careful when scraping and sanding so as to not distort the profile of the handrail. You are now ready to remove the bending guides from the stairs, and finish your installation.
Always wear safety glasses when operating power tools and use tools in the manner they were designed.
Neither Stairway Creations Supply or any of its employees assumes any liability for the installation of products purchased from our company. Installation instructions are general because each and every job will be different and certain conditions will have to be adapted to the individual situation. We assum no liability for use or misuse of any equipment or products.
Please make sure you comply with all building codes.
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