Hi all,
I'm currently in the research phase of designing a timber framed barn using Douglas Fir for structural members as well as external cladding (wany edge).
I did search the permies forums to see if this has come up before, but found nothing, so please forgive me if I failed to use the right search terms.
Everything I read online from mainstream sources here insists that you must ONLY use stainless steel fasteners, particularly when attaching cladding boards to the frame. Reasoning being that apparently the properties of Douglas Fir timber will cause mild steel/zinc plated/galvanised metals to corrode, leading to ugly staining as well as weakening of any metal fasteners used.
I have a problem with this uniformly parroted consensus - ie the significant number of North American buildings 150+ years old framed and/or clad in Douglas Fir that are still standing today in excellent structural and aesthetic condition... Stainless Steel as we know it today of course didn't really exist until the 20th Century!
I'm writing from the UK where timber framed (or clad) buildings are largely seen as a fairly radical and unconventional experiment... In a lot of cases timber framed houses are barely (or not at all!) mortgageable by mainstream banks due to concerns about longevity and durability. Ignorance of the irony of this attitude is widespread... in a country where some of the oldest buildings still standing are 1000 year old half-timbered medieval constructions.
Please can some of those on the other side of the pond to me with an actual wealth of experience and knowledge on this topic school me on the facts of this matter?
Will mild steel/zinc plated/galvanised fasteners cause problems when used with Douglas Fir, or are people simply wrongly lumping Douglas Fir in the same basket as tannin-rich timbers such as oak?
Does Douglas Fir cause a cosmetic reaction with ferrous metals that is harmless to both the fastener and the timber or is there some non-cosmetic merit to the advice to stick with Stainless Steel only for metals in contact with this timber species?
Many thanks in advance.
