Wood siding species and back-priming?
canoehead2
| Posted in Construction Techniques on
I’m wondering what people’s thoughts are on wood siding species choice and backpriming.
I’m in Ontario, Canada. Cold winters, hot & so so humid (but not overly wet) summers. I’ve always used oil-backprimed pine for projects in the past but am wondering if I can save time by using white or yellow cedar cedar that isn’t backprimed. I would always install over furring strips and, of course, with Tyvek wrap under that so given the climate my gut tells me that it would still be durable.
One thing I hate about pine is the multiple coats of bull’s eye I seem to need block knot bleeding.
Thoughts?
Replies
canoehead2
Here's my take on the subject..
Wood as it comes from most lumberyards is around 19% moisture.. siding included.. it will eventually get to around 7 or 9 % moisture and vary with the outside moisture to a degree, (it may get as high as say 15 % miosture during protracted rainy periods.. but once the bound water is released and it dries to the that 7 or 9 % quickly return to that level..
Untill it gets to that 7 or 9% moisture level you risk trapping water inside if it's properly sealed. then under the direct exposure to sunlite the moisture in that wood will want to blow off any paint that's applied.. if the weak area is the outside that's where paint will blister.
Aagainst that wood that isn't back primed will absorb moisture from the back and possibly cause paint to blister off the front under similar circumstances..
MY approach has been to back prime but leave the front exposed untill it reaches stability and then paint the front.. a rough guildline is wood dries out properly one inch per year..
That will also help your issue of bleeding
What you say about siding and MC is based on th e old oil based paints. Latex paints will let moisture pass through without blistering if it has a good bond.
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Thanks Frenchy. I think I'l go with latex priming though. The exposure gets tons of direct sun and I think latext will be more flexible under the expansion/contraction that will occur.
Have you considered Hardie siding materials?
Have never tried Hardie. How to I cut it with shears as per the Hardie site? Will it be a clean cut? (I don't want to use my saw because of the Silica dust).
Almost ANY wood siding can be ordered pre-primed nowadays, so time is less of an issue. I can't remember the last time we installed siding without it being back primed. Pick your species and quality, order it, then when it come in use it.
BTW, you do not want to use cedar unprimed over Tyvek. The cedar tanins rot the tyvek out according to testimony here.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Tannins rotting Tyvek!? Wow. My neighbour won't be happy about the _undipped_ cedar shingles that were stapled (without stainless I might add) to his whole house _without_ any furring. In fact, the sprayed on finish (looks something like Sikkens) is already peeling pretty bad.