Wood Trusses for Car Wash/Gas Station
Wood Trusses for Car Wash/Gas Station
(OP)
Has anyone ever designed wood roof trusses for a car wash? 5/8" "Green Board" will be attached to P.T. 2x4's attached to the bottom chord of the trusses. Should I be concerned with moisture content even with green board attached? Thanks in advance.





RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
There is a wet use factor in the timber code also that may be applicable in this case.
csd
RE: Wood Trusses for Car Wash/Gas Station
Mike McCann
McCann Engineering
RE: Wood Trusses for Car Wash/Gas Station
The attic space of the roof will be vented. My concern is how well green board actually prevents moisture from penetrating into the attic space and if the moisture content in the attic space will exceed 19%.
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
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For the moisture content of wood to be >19%, the Relative Humidity would have to be >90% for extended amounts of time. With proper ventilation, that probably wouldn't occur.
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
I've had people approach me about using treated lumber trusses to create exterior footbridges. In researching the idea, our engineering rep at Alpine basically said truss plates should not be used in environments where the trusses will see cycles of wet and dry (ie, rain) because the teeth are much more likely to loose their "bite" from the local shrinking and swelling associated with wetting and drying. I got the impression that it would be much more so than the NDS Cm reduction for nailed connections.
RE: Wood Trusses for Car Wash/Gas Station
Additionally, I would tell the Owner (in writing) that the longevity of the wood truss system depends upon the quality of maintaining the attic space at nature moisture levels and if joints, green board and vapor barrier are not maintained to near perfection, he may find himself replacing the roof. Although the initial capital costs are lower, maintainance and replacement costs may exceed those of say a precast roof.
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
All five of the previous carwash projects I've dealt with in the past used precast concrete roof plank. One of the buildings has been operational for over 40 years, the equipment has been changed twice but the building is still functioning.
Let's face it, each material has its' place in the market. IMHO precast concrete roof plank suit carwashes better and will last longer than wood trusses.
RE: Wood Trusses for Car Wash/Gas Station
RE: Wood Trusses for Car Wash/Gas Station
RareBug
RE: Wood Trusses for Car Wash/Gas Station