TIMBECK Profiles - Two Alternative Fixing Methods
All TIMBECK tongue & groove profiles have been designed with an offset groove which allows the head of a fixing to be concealed by the adjoining board. When it is considered appropriate (as assessed under these guidelines), concealing of fixings can be incorporated into the specification. When the concealed fix option is considered unsuitable or inadequate, face fixing of the same offset profile is appropriate.
Typical Conceal Fix application.
The fixing is through the thinnest section
of the board and the head must be driven
flush to allow the tongue & groove to properly
Typical Face Fix application to the same profile.
The primary and secondary (when required) fixings are through
the full thickness of the board and have the capacity to offer significantly
greater holding and restraining power.
The Face Fixing Option
The interlocking tongue & groove detail on TIMBECK cladding profiles allows the heads of fixings to be concealed but it restricts the securing of the overall cladding to just one fixing per board at each stud (or batten). This degree of restraint is considered quite adequate where nil or very minimal movement of a board is likely to take place.
Even though Western Red Cedar has one of the lowest shrinkage rates of any timber specie, if it does absorb moisture, some degree of movement is inevitable. TIMBECK does not recommend relying on just one fixing through the thinnest section of the profile under those circumstances.
Adopting more substantial fixings (deformed shank, screw thread, larger diameter head) and applying them through the face of the board is recommended.
The decision for one OR two face fixings at each support point is for the specifier and should be influenced by degree of exposure, direction of exposure, likely integrity of future maintenance and width of the profile. With Face Fixing, the heads of the fixings are obvious on the finished surface and this is the only recognisable difference between Face and Concealed Fixing options.
In many cases, the expression of the nailing pattern will be an attribute of the overall design when choosing the appropriate option. This is often the case particularly when specifying fixings with larger head diameters.
Face Fixing can also easily accommodate any need for additional nail holding as might be the case in some high wind regions. Another advantage of Face Fixing is its suitability to a wider range of board widths than can be achieved with concealed fixing.
TIMBECK’s recommendations for fixing Western Red Cedar claddings lie with both Face Fixing AND Concealed Fixing depending on the location, exposure and future maintenance levels of the application.
Either option, complimented with penetrating oil finishes, (one coat as a factory applied pre-finish with a second coat applied on-site after installation) will provide the optimum exterior cladding.
The Concealed Fixing Option
In instances where cladding boards are prefinished with a film forming coating and there is a preference for not penetrating that film, concealed fixing is appropriate. However, concealed fixing of wider boards should be restricted to wall areas that can be well maintained or alternatively, are reasonably well sheltered areas – ie under wide overhangs or facades adjacent verandas.
The Decision – To Conceal Fix OR Face Fix
In considering all aspects at the extremes, the fixing requirements for a 100 mm Western Red Cedar internal panelling will be totally different to that required for a poorly maintained 200 mm hardwood cladding exposed to the worst of the elements.
While design trends may suggest that the hiding of board fixings are the fashion today, the overall parameters as outlined here do not change. As attractive as concealed fixings may be, they are quite inadequate for many situations. Concealed fixings are also located in the thinnest portion of the board which is counter to the requirements of increased performance.
Furthermore, while deformed shank fixings (nails & screws) do provide better hold, trying to work a countersunk screw version into a conceal fix detail is extremely impracticable and very difficult.
Developments in Fastening Technology
One thing from which the Timber Products industry has derived significant benefit is the technological progress that has been made by the fixing manufacturers. The days of relying on a range of smooth shank bullet head nails to solve all fixing requirements are long gone and specifiers are encouraged to explore the range of non-ferrous fixings from silicon bronze and stainless steel manufacturers.
One excellent example is this dual thread stainless steel screw from Spax Pacific which is an ideal choice for face fixing claddings.
The secondary thread is at a different pitch to the initial thread which assures a rigorous hold between the screw and the cladding.
The relatively small diameter head is very conducive to a face fix application with timber cladding.