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I did that many years ago with some pine I had cut and put my clearest prettiest boards in the attic above my garage. I ended up getting a lot of black spot/mold in the boards. I suspect it was because of high humidity. It may have been a unique situation, but that is what happened to me.
Just one caveat; Don't place any weight on the chord of truss roof system. Even a typical 2X6 ceiling joist (instead of 2X10) found in many attics won't support heavy loads.
Joe
Joe
When I built my shop, I called the truss engineer who sealed the plans. My trusses (spanning 24') had 2X4 chords. He told me that had I specified 2X6 lumber for the chord it would support almost anything I could put up there. Is your admonition a DAMHIKT type thing, or do you have extensive truss design experience and my guy was kin to Fibber McGhee?
I think the issue is high humidity and moisture content in attics, at least it was for me with the pine.
Roof Framing
has some answers, . . but if you have trusses, you don't have ceiling joists (not for the ceiling directly below your roof attic, that
is). You have the bottom chord of the truss.
Frankly, for vertical loading, the bottom chord is typically
the weakest member of the truss. When it fails, the web
members of the truss begin failing, along with the
connections, and . . . of course, finally, the the top chord
members. Meanwhile, your ceiling has become a mess.
You will notice, HVAC folks prefer to hang their air
handlers, etc., from the top chords rather than sit them on
top of the bottom chord. This has a secondary advantage of
further isolating the vibration from the ceiling membrane,
but the principal advantage is the better positioning of the
added weight load.
This is not to say that bottom chords can not be designed to
carry a floor load. They can. But in most housing, they
are not. Christmas trees and insualtion not yet installed
is about the best use for storage on the bottom chords.
has some answers, . . but if you have trusses, you don't have ceiling joists (not for the ceiling directly below your roof attic, that
is). You have the bottom chord of the truss.
Frankly, for vertical loading, the bottom chord is typically
the weakest member of the truss. When it fails, the web
members of the truss begin failing, along with the
connections, and . . . of course, finally, the the top chord
members. Meanwhile, your ceiling has become a mess.
You will notice, HVAC folks prefer to hang their air
handlers, etc., from the top chords rather than sit them on
top of the bottom chord. This has a secondary advantage of
further isolating the vibration from the ceiling membrane,
but the principal advantage is the better positioning of the
added weight load.
This is not to say that bottom chords can not be designed to
carry a floor load. They can. But in most housing, they
are not. Christmas trees and insualtion not yet installed
is about the best use for storage on the bottom chords.
J
jeff...
Travis, your right, SYP is famous for developing blue stain specifically when it's cut in the summer months and the humidity is high. Some people sell blue spot pine it as denim pine :slap:.
SYP really should be dried quickly, at higher heat and lower humidity than hardwoods. This is one reason I don't mess much with pine, it's too easy to black spot. Another reason is the pitch should be set by bringing the stack upto 180 degrees and maintaining for at least 24 hours, if not then when the wood gets warm, you just might have a sticky sap mess on your hands, DAMWIKT :roll:.
But for construction material material pine really can't be beat. I did build a pantry out of SYP but only because my wife insisted it be made of pine. It was cut in the winter months after that big ice storm several years ago, my sister lost several big pines that I took to Ted and had milled into 4/4. I stacked and stickered in my shop with a fan blowing through it stack. I did heat the stack up before I machined the lumber but am not going to mention how I heated it up because it's a fire hazard.
Just my 2 cents...
All unconditioned spaces in this area are high in humidity, but can be controlled somewhat with air flow help.
Fortunately, pine drys relatively quickly, so problems related to drying to quickly should be minimized.
In a kiln, it is not the heat that drys lumber - it's the airflow across (and inbetween) the stacks. Too little air flow, at temps between 70 - 100F, and you get a mess of mold on the wood. Too much airflow, and you end up with case hardening.
If you're talking about anything more than a few boards, I would suggest initially drying the lumber in a covered area downstairs (such as a garage) where you can arrange (and measure) for airflow through the stacks, and also us a dehumidifier to keep the humidity level to 50% inside the garage.
After the lumber drys down to 25% moisture content or less, then move it up into the attic, sticker it, and forget about it.
Scott
In a kiln, it is not the heat that drys lumber - it's the airflow across (and inbetween) the stacks. Too little air flow, at temps between 70 - 100F, and you get a mess of mold on the wood. Too much airflow, and you end up with case hardening.
If you're talking about anything more than a few boards, I would suggest initially drying the lumber in a covered area downstairs (such as a garage) where you can arrange (and measure) for airflow through the stacks, and also us a dehumidifier to keep the humidity level to 50% inside the garage.
After the lumber drys down to 25% moisture content or less, then move it up into the attic, sticker it, and forget about it.
Scott
actually drying rate has several factors that influence how fast wood dries.
1-The relative humidity of the surrounding air
2-steepness of the moisture gradient
3-the temperature of the wood.
The drying process implements air flow to influence RH and heat accelerates the water movement through the moisture gradients. The higher the temperature of the wood the faster the water moves from wetter areas to drier areas
too low an RH and you have excessive end and surface checks
too high a temperature collapse, honeycomb or strength reduction will occur.
case hardening is a result of NOT equalizing your load at the end of the cycle due to uneven moisture gradients.
the key reason for kiln drying pine for use in furniture is to set the pitch and usually this needs to have a starting temperature of 150F
1-The relative humidity of the surrounding air
2-steepness of the moisture gradient
3-the temperature of the wood.
The drying process implements air flow to influence RH and heat accelerates the water movement through the moisture gradients. The higher the temperature of the wood the faster the water moves from wetter areas to drier areas
too low an RH and you have excessive end and surface checks
too high a temperature collapse, honeycomb or strength reduction will occur.
case hardening is a result of NOT equalizing your load at the end of the cycle due to uneven moisture gradients.
the key reason for kiln drying pine for use in furniture is to set the pitch and usually this needs to have a starting temperature of 150F
J
jeff...
I'm glad you experts chimmed in here - this is here I exit stage left...
Thanks
Thanks
Kyle and Scott et al
I checked the temp in my attic today. With good sun outside and outside temp of 77 degrees that attic temp was 103, 25 degrees higher than outside and the rh was 35%. I'll take Scott's advice and dry the BW down to 25% or so outside and then sticker it in the attic with a box fan on it to move the air. Since the attic cools down at night and the rh rises to the ambient rh outside, I hope I won't get case hardening. In any case, I'll test a piece or two at the end to see if case hardening has occured. If so, would spritzing the wood on both sides with a spray of water eliminate the case hardening? When the BW is dry I'll move it to my shop, which has a DH running continuously. I'll let you all know how long it takes my attic to get this wood dry.
Regards,
Rocker
I checked the temp in my attic today. With good sun outside and outside temp of 77 degrees that attic temp was 103, 25 degrees higher than outside and the rh was 35%. I'll take Scott's advice and dry the BW down to 25% or so outside and then sticker it in the attic with a box fan on it to move the air. Since the attic cools down at night and the rh rises to the ambient rh outside, I hope I won't get case hardening. In any case, I'll test a piece or two at the end to see if case hardening has occured. If so, would spritzing the wood on both sides with a spray of water eliminate the case hardening? When the BW is dry I'll move it to my shop, which has a DH running continuously. I'll let you all know how long it takes my attic to get this wood dry.
Regards,
Rocker
J
jeff...
Hey Scott / Kyle I understand there are lots of ways to dry lumber. But was wondering if there is a chart that gives the maxium safe allowable water loss per day for differnt hardwood species?
Thanks
Thanks
Jeff, there is a wealth of information available, including charts with recommended MC removal rates. The USDA, Dept of Forestry has very good information contained in several publications. One of the most commonly referenced is "Drying Hardwood Lumber" by Denig, Wengert and Simpson (USDA Technical Report FPL GTR 118).
This publication provides a thorough background and guide to drying hardwood, and it goes into detail about the concepts elaborated on by Kyle and I in our earlier posts.
There is also good all-around information about drying lumber in the USDA "Air Drying of Lumber" publication (USDA Technical Report FPL GTR 117).
Nyle Corporation (manufacturer of dehumidification kilns) has published information as well that provides guidance regarding species, thickness and recommended MC removal ranges. I am sure that there are other sources as well (and perhaps Kyle can chime in here); these are the ones that I use.
This publication provides a thorough background and guide to drying hardwood, and it goes into detail about the concepts elaborated on by Kyle and I in our earlier posts.
There is also good all-around information about drying lumber in the USDA "Air Drying of Lumber" publication (USDA Technical Report FPL GTR 117).
Nyle Corporation (manufacturer of dehumidification kilns) has published information as well that provides guidance regarding species, thickness and recommended MC removal ranges. I am sure that there are other sources as well (and perhaps Kyle can chime in here); these are the ones that I use.
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