I. Provisional fixing:
After the bending Bendywood®-handrails should only be fixed provisionally to the banister, so that they can shrink along their length.
Handrails that are bent at 12% moisture content will shrink in length by up to 0,5 cm per running metre until the equilibrium moisture content is reached or until the wood moisture content has adjusted to the indoor climate.
II. Final assembly:
Only after this the handrail can be taken off, sanded (if necessary), finished and permanently fixed.
Start with a fix mounting point halfway its length and mount the handrail from there towards the ends in such a way that it can still shrink a bit along its length, especially in the case of long handrails. It is best to use handrail supports which you can provide with slotted holes.
Please consider that a 6 m long handrail, for instance, will further shrink by up to 1 cm (on its total length) within the first year after final assembly.
The shrinkage can be greater if the ambience is heated or air-conditioned a lot without regulating the equilibrium moisture content.
Only in the following cases the problem of shrinkage doesn’t occur:
- In case the handrail is bolted down to a continuous metal rail of the banister (from below) at intervals of about 20 cm. Only this type of mounting prevents shrinkage in length: however, only use strong, deep penetrating screws, especially for handrails with a diameter of ø42 mm or more;
- In case the mitre joint is under tension: this occurs when bent parts (which always open up a little) exert pressure on the mitre joint.
III. Mitre joints:
Mitre joints at the ends should be avoided: the risk that they will „open up“ in the long term is high.
In case mitre joints cannot be avoided, there are 2 options:
- Mitre joints with synthetic resin glue and a threaded rod:
- Drill sufficiently big and profound holes into the handrail ends that need to be jointed;
- Fill these drill holes at both ends with a synthetic resin glue and insert a threaded rod, which diameter should be a bit smaller than the one of the drill hole;
- Press both handrail ends together with clamps and keep them in position until the glue has dried.
The use of a threaded rod as well as the use of synthetic resin glue are both absolutely necessary to prevent the joints from opening up.
- "Open" mitre joints or "open" butt joints:
Such joints are secure and in certain cases also decorative (when combined with glass elements, for instance).
IV. Staining and varnishing:
Do not use water-based products, only synthetic stains and varnishes, such as "Danish Oil" (Rustins) for instance, especially when it concerns thin sections. Thicker sections, such as handrails for instance, better endure water-based substances as long as these are dried well immediately after their application. A deep penetration of water should be avoided!