wet service factor: what exactly is "extended period of time?"
wet service factor: what exactly is "extended period of time?"
(OP)
I'm designing a covered screened-in porch with a long span, and using an LVL would be ideal for the roof edge beam. It would be covered by 1.5 ft of overhang. I'd really like to stay away from wolmanized PSLs as they mean using extra corrosion-resistant hardware (read: much more expensive) and they're not readily available. The required span makes using PT lumber difficult.
So, background in place, here's the question. Is this beam even considered moist-use? It seems to me that it couldn't get all that wet, especially for an extended period of time like the NDS says. But what exactly is that mysterious extended period of time? And does the problem go away if the beam is protected by something like a miratek trim board?
thanks,
Linnea
So, background in place, here's the question. Is this beam even considered moist-use? It seems to me that it couldn't get all that wet, especially for an extended period of time like the NDS says. But what exactly is that mysterious extended period of time? And does the problem go away if the beam is protected by something like a miratek trim board?
thanks,
Linnea






RE: wet service factor: what exactly is "extended period of time?"
RE: wet service factor: what exactly is "extended period of time?"
It depends on your location. Inland regions may be dry service whereas coastal regions could be considered wet service. You haven't told us where the structure is located. The safest route is to assume wet service.
BA
RE: wet service factor: what exactly is "extended period of time?"
RE: wet service factor: what exactly is "extended period of time?"
To wit: An extended period of time is defined as a period of time that is extended.
See, that was simple!
On a more serious note, is this an application for more local and ample use of moisture barriers in order to dissolve the issue?
As an example on another topic, retaining walls. When water table behind the wall (for some applications) indicates a very high EFP, we'll go to extreme measures to reduce the water as that is usually much cheaper than designing a larger concrete wall. The extra drain tile, engineered backfill, etc are usually pretty cheap.
Good Luck.
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: wet service factor: what exactly is "extended period of time?"
slta...the explanation I got from APA was that they cannot accommodate all of the variables of environment, exposure, protection, etc. in a given locale or on a given project site, so they will not quantify exposures or limits.
This is what the Southern Forest Products Association says about Cm....
I get from this and other references that Wet Service conditions refer to intermittent, but repetitive wetting in an exterior application.
I would not consider your application to be wet service, but you would do well to protect yourself (and the beam) with some ancillary waterproofing, as Qshake noted.
RE: wet service factor: what exactly is "extended period of time?"
RE: wet service factor: what exactly is "extended period of time?"
Personally, I would still treat the wood with some form of a vapor barrier be it preservative, oil, ... whatever, if you want to use the dry condition in order to try to maintain the low moisture content within the wood. I would stay away from paint, but that's just me.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: wet service factor: what exactly is "extended period of time?"
RE: wet service factor: what exactly is "extended period of time?"
RE: wet service factor: what exactly is "extended period of time?"
As for treatments, coatings, and preservatives...each can work well in its own right; however, you must select the correct one depending on the exposure, the wood type, and the potential for wetting/drying. In some applications, acrylics work well on wood...in others, they promote decay. Penetrants will generally work in most applications (oils, oil stains, etc.).
RE: wet service factor: what exactly is "extended period of time?"
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RE: wet service factor: what exactly is "extended period of time?"