Hello again. I’m trying to understand wood rot. Obviously its caused by moisture but it seems from what I’ve read that rot is an organism feeding on the wood and as such needs warmth as well. Does this mean that wet wood kept at say 25 or 30 degrees won’t rot or won’t rot as quickly as damp wood at 60 or 70 degrees? I’ve got scraps of wood from my renovation in my yard that have been out in the weather for about 8 months. They don’t seem to be rotting. The solid scraps and plywood scraps are discolored but seem solid which surprises me. How long does it take for rot to start? As i’m siding I’ve got most of the plywood covered with tar paper and whats not covered with tar paper is covered with the yellow densglass gold sheathing. After one nasty storm where some areas of plywood under the densglass gold got wet i started worrying about its condition if parts were getting wet when it rained. I cut a small section of the densglass out to look at the plywood and it seemed fine. Solid when hit with the claw of my hammer. Plus whenever I cut the openings out to put the windows in the plywood always looks fine. So how long does it take for rot to start? Does the fact that no work has been done inside the addition yet help prevent rot since it might be easier for the wood to dry plus ,again, no heat and average temp between 30 and 40 degrees here. Believe me I’m glad I’ve had no problems but I also want to understand this so I can prevent problems in the future. Thanks again.
Richie
Edit. Oh yeah, i forgot, I saw on This Old House where they got beams for a timber frame from logs fished out from the bottom of rivers. This really confused me because this wood has been soaking on water for years and is fine. What am i not understanding?
Edited 1/13/2009 9:10 pm ET by Richie921
Replies
submerged logs are deep enough that they are too cold for the micro-organisms to grow.
Various kinds of parasitic micro-organisms feed on wood. To grow and multiply, they need moisture, food ( the wood), warmth, and air.
Wood kept below about 12% MC by weight is unlikely to harbour growth. since your space is unfinished and presumably unheated, when moisture gets to the wood, it can dry again and meanwhile is too cold for molds, fungi, and bacteria to grow and form colonies. Some of the wood you have may have been treated in one way or another also.
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Thanks. So rot is actually an organism eating the wood? The plywood I have is 1/2 inch and 3/4 inch rated sheathing. Is that usually treated in any way? Is it the same with mold as far as needing warmth to grow. I'm an electrician and have torn into a lot of houses. I have yet to see mold in the old, uninsulated houses but find it more often in newer homes. Thanks again.
Edit: I was typin this after piffins response before i saw the others. Does rot set in faster in plywood or solid wood or it makes no difference. Thanks.
Edited 1/13/2009 9:37 pm ET by Richie921
actually what you are calling rot is not a single organism, but the result of one of many ( perhaps hundreds of different kinds including mold, fungi, and bacterium) micro-organisms (MOs) that commonly feed on wood.I think there are a few reasons why plywood is slow to start rotting.One is that most structrual exterior ply is fir, which has some tannins and resins that are acidic and resit the growth of these little MOsAnother reason is that ply starts out as a very dry wood and then the glue that is used between plies of ext ply wood is water resistant so moisture is slow to penetrate it.There may also be some effect of the heat that is part of the manufacturing process in destroying some spores in the wood.Plywood will rot though.
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So when wood is pressure treated the treatment inhibits the growth of these microorganisms? Is that how pt can stay out in the weather and not rot?
when wood is pressure treated the treatment inhibits the growth of these microorganisms?
Yes.
It also changes the "taste' of the wood, which cuts back on infestation by termites, ants, bees, and the like. Incestivorous infestation provides (or invites) additional surface area for the microorganisms which can then "feast" on the exposed wood.Occupational hazard of my occupation not being around (sorry Bubba)
Thanks guys. It sorta makes sense now. I'm still amazed by that whole "using wood thats been underwater for a hundred years".
fungi need more oxygen than is found deep underwater.
also, a lot of the sinker logs were the ones that were too dense to float to the mill ponds, they were the densest heartwood.
k
My house is sitting on wood piles that have been there for 150 years. As long as they remain below the ground water level the microbes don't have oxygen and I'm OK. There are churches in Europe that are 1000's of years old built the same way.
Much like Venice!
I will take your word on the 1000 year old church- I wouldn't know-
on the other hand I know exactly what you say is true with regaurds to lighthouses built on the north carolina outer banks VERY heavy masonry structures built on wooden cribbing foundations---survive quite a long time---one was actually jacked up and moved( about a mile?) a few years ago--built on a barrier island- the sea had encroached enough that the light house was threatended---- i wonder if the new foundation at the new location was constructed the same way?
stephen
Richie921
When we made the shingles for MT. Vernon ( Yes, George's house) we use old growth cypress that had been in the rivers under water for 200 years. Looked kinda rough on the outside, but on the inside was just as solid as the day it was cut. We had to use old growth to meet the specs from the arch., 30 growth rings per inch!! We made 54,000 hand split, draw-knifed shingles. The first 3-4,000 were fun doing it the "old way" after that it was just repetitious drudgery, one after another after another...... Same was true with the Chowen county court house in Elizabeth City, NC. ( 39,000) Maybe I try to find the pics of the logs (some as large as 5' across) as we unloaded them from Fl. As long as the wood stays completely wet or completly dry it does not rot (as fast) Bill D. Quality Wood Chips
I thought that you used white oak. Or was that a different job.I think that I remember you posting that you had a bunch left over if anyone needed them..
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Yes, that was a different job. That was making riven white oak clapboard. I've really no idea how many of those I've made. No where near 54.000. More like 8.000 maybe. The pic is of a much younger me riving some of my first clapboard. Yes and I had a bunch of short pieces left over. Tho I don't remember posting that??? But then that was some time ago.Maybe that was the post of blowing-up logs with black powder ( Now, THAT was fun!!). I wonder if I can post the video of it that I have...hmmmm....?? Bill
For a video post it on youtube and post a link.Huck as done a number of them..
William the Geezer, the sequel to Billy the Kid - Shoe
That was an old VHS tape. I would not even know the first step in even getting it on the computer. I'll have to ask my son, he knows a lot more than I do on this stuff. But, yea it was fun and saved us a LOT of work; what would take me half a day to spilt one log 2-3' dia. x 12-14' long, using gun powder was only 30-45 min. and that was half and quarter the log. The local Amish taught me about it when logs were too big for their carriage at the mill. Yes I notified the local constable when we "popped" a log. Bill D. QWC
Yes, rot is an organism. Yes it grows better in warmer climes. Warm, dark & moist is what spurs the growth of rot. (I can just hear the undercuts lining themselves up on that one)....
Anyhow, if the plywood is exterior ply,cdx, It can withstand quite a bit of weather before any kind of rot sets in. The key is to allow wood to dry out, to ventilate it. There are many factors that speed up or slow down the process of rot. Temperature, drying out, ground contact speeds it up, There are certain woods that are more resistant to the organism because of cell structure, oils, acids etc. that are part of its makeup.
Rot organisms don't live down in the bottom of lakes & rivers. They need air to propagate. Also it's usually too cold way down there.
There's very little oxygen deep in the water. Similar to how a shipwreck will survive hundreds of years at the bottom of the ocean, but as soon as it's brought to surface, it will quickly decompose.
What's that British ship, the Mary Rose or something?
Here's one of my favorite examples of wood preservation in deep water.
The Vassa was built by the Swedes back in the 1600s and sank on it's maiden voyage. With dual gun decks and a narrow hull, it was too top heavy. With too little ballast to compensate, when the sails were raised the boat listed and water poured in through the lower gun ports and the ship flooded and sank.
It remained underwater for 333 years. Deep enough and cold enough to remain well-preserved.
This ship is just gorgeous. The tooling marks on the wood, the joinery...this ship is simply stunning.
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I saw the Vasa last summer! That was one of the most interesting exhibits I've ever seen. The Sacandinavians know how to do museums.However, if my memory serves, in this particular case, it was not water depth that kept the Vasa from rotting, but a combination of the naturally cool Baltic Sea water and it's low level salt content. The Vasa was actually in pretty shallow water. We're so used to seeing examples of astonishing engineering successes in old & ancient building that it was sort of refreshing to see a classic "Doh!" moment in history.
Yeah, I think it was around 100' deep. Or 30 meters s they say over on that side of the Atlantic.<g> Not "deep deep" but thankfully in this case, deep enough.
The Vasa sank in relatively fresh water. Though the lower density of the water may have contributed to its demise (lower buoyancy) the fresh water helped preserve the ship because it didn't support shipworms which otherwise would have consumed it.
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Wow, those photos are amazing. The ship looks beautiful. So how long does it take for a piece of wood (ply or solid sawn) to rot that occasionally gets wet like my situation with the sheathing? Also, I'm putting veneer stone on a part of the house which I understand can cause rot because it traps moisture. Any tips other than good flashing techniques for this? I've been using two layers of tar paper under the vinyl (I'm an anal worry wart about moisture and rot) so I was going to do the same under the stone. I don't want moisture to be trapped though and from what I've been reading moisture WILL get behind the stone. Unlike the vinyl though which lets the wall breathe and dry the stone is like the EIFS which traps moisture and we know what problems that has caused. Any advise is appreciated.
Richie
You want a drainage plane and weepscreed. The double layer of tarpaper will act as a defacto drainage plane, although there are other products specific to that purpose.
make sure that any water that does find its way in has a way out at the bottom.
k
Is the space between the two layers of tar paper a weep screed?
No. The space between the two layers of tar paper is a drainage plane (of sorts).
A weep screed is a means of allowing the water that is flowing down the drainage plane to exit at the bottom. It is usually a straight piece of metal (a screed), with weep holes.
The trick with stone veneers is that visually, you often want them to look like the stone is sitting on the ground, but functionally, you want the weep holes to have room to weep.
try posting a question about stone veneers/drainage plane/weep holes. I'm sure there are folks who know more than me. My knowledge is based on stucco, which has similar issues.
k
edit- my no at the top was not to the previous post, but to the question the op asked me...
Edited 1/14/2009 4:16 pm ET by KFC
Ahhh...gotcha. The stone is gonna end about 3 feet off the ground above the foundation so I guess I have to put a screed in across the wall similar to a starter strip and go from there. Thanks
Again, I don't know much about stone veneer, you may want to post that as a separate thread. But it sounds like you've got the idea. They may call the starter strip something different for stone, or it may simply be z-flashing with weep tubes, I don't know.
k
Oh, and out of curiosity, what happens for the three feet from the bottom of the stone to the ground? Does the stone just visually float at that height?
k
Yeh...the foundation is about three feet high painted concrete. The stone is gonna be the thin veneer style that hangs on wire lath and a scratch coat.
Edited 1/14/2009 5:00 pm ET by Richie921
Functionally, that's great. A lot of people want to run the stone all the way to the ground, so it looks like a load-bearing stone wall, but that doesn't allow the water to drain away.
Basically, the outer layer of your felt is going to adhere to the scratch coat to a large extent, and pretty much become one with the cement/stone layer.
the wrinkly space between the two layers is the drainage plane.
the inner layer is your moisture barrier.
And actually, this comes back to your original question about rot, in a way. There is no question that some moisture will get in there at some point. (You do every thing in your power to avoid it, of course. Flashing details are critical.) But the biggest rot issues are when that moisture gets trapped in there. As long as you give it a path and an exit, you'll be ok.
k
Oh and you said u have experience with stucco. What is the blue stuff they painted on my neighbors house on the fireboard to prep for stucco? Any idea?
What is the blue stuff they painted on my neighbors house on the fireboard to prep for stucco? Any idea?
Blue stuff? Don't know. Borate treatment? Spray-on waterproofing? Got me.
k
Just have to ask? is there a brick ledge or support to take the weight of the stone? If it end 3 feet up with no support, would you not worry about it peeling off than rot?
Again, I'm not a stone guy, but my understanding of stone veneer is that it acts like stucco, as opposed to brick. The lath is anchored to the sheathing enough to carry the weight of the whole assembly.
Brick needs a support ledge, because there's an inch air space between the wall structure and the brick- they're structurally separate.
But seriously, wait until the masons weigh in on this. I may get reamed for what I've been saying. Or start a thread with the stone veneer questions- the masons may not be slogging through a 40 post thread on rot...
k
No, no ledge. It "hangs" on the wall. Lath nailed into studs followed by a scratch coat of mortar followed by the veneer stone adhered with mortar to the wall. Sort of like tile.
Richie
The stone masons at the job I'm at now put two layers of tar paper over the housewrap that was already installed. Mesh over that with a scratch coat, and then stone. It looks really good, but with no treated joints, I'd think that water would get in there some how. I thought about doing the same thing once, but at $500 a pallet minimum order, I came up with less expensive ideas. I really like the look, though.
Water will get in for sure. The "cultured stone" is water permeable, even if the joints are sealed.
Hence the multiple layers of building paper/ housewrap, and the weep screed.
k
In practically all cases plywood sheathing will delaminate long before it rots. Delamination is the thing you need to be concerned about first. And most grades of sheathing are rated to stand up to direct weather exposure for several months.
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Thanks Dan. As far as the stone, are two layers of tar paper my best bet?
Edit... It makes me feel better too that it can be exposed directly for several months cause the frame was finished in early June. Its all covered with tar paper or the fire board but like I said I'm sure some moisture gets there ocasionally (heavy rain) but delays and me working by myself to put the windows in and side it have caused it to take a long time. Around the corner from me a house wa framed about a year before mine with half covered with fireboard and the wood with tyvek and they r just starting to side it now (with EIFS stucco) so I guess I'm not the only one to have delays from frame to finished siding. They painted a blue paint on the yellow fire board last week...not sure what it is. Anyone know? I cut ou a small square of fireboard to check the ply behind it and it looked fine. I'm just a worrier cause I don't know a lot about wood other than drilling through it or nailing into it.
Edited 1/14/2009 4:23 pm ET by Richie921
I'm not a stone guy. All I know is that you want a water barrier behind it AND weep holes at the bottom.
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If you go over the JLCONLINE.COM and look under Archives.http://www.jlconline.com/cgi-bin/jlconline.storefront/496fbaa10fab9aae27170a32100a06c8/Catalog/1011StuccoLook at the first 3 articles. IIRC they are $5.95 each, but the one is free..
William the Geezer, the sequel to Billy the Kid - Shoe
Thanks Bill. I wish I never let my subscription to JLC expire. Some of those articles would be good to have now.
Where is this museum?
In Stockholm.
Thanks Mongo - I've been in the Vasa Museum too -
Jeff
mongo-- thanks for the pictures-- I am amazed by wooden sailing ships---- I once read somewhere that we should consider them the equivalent of todays space shuuttle--both from an exploration standpoint--and that they were the most complex man made objects of their day
stephen
Rot needs both moisture and oxygen. That's why piers break at the point between hi and low tides. They get wet, then dry out. Repeat.
Water is a great way to preserve wood, if you leave it completely covered!
Logs submerged under the right conditions don't rot because they can't get enough oxygen. Also, it helps if the water is cold.
I'm not sure at what temperature rot organisms stop operating -- pretty much they stop below freezing, but probably rot can occur reasonably easily at 40F, and certainly at 50F. But things tend to rot faster in warmer temps.
The type of wood makes a significant difference in the rate of rot -- some woods are quite rot-resistant, others seem to rot overnight. But in reality it takes months if not a year or two for significant rot to occur in a temperate climate.
The main controllable factor with regard to rot (besides the wood used) is moisture. If (untreated) wood remains damp for long periods of time in above-freezing temperatures it will almost certainly begin to rot. Short periods of dampness, of course, aren't good for the wood, but are very slow to promote rot.
The scraps of wood in your yard are slow to rot in part because they don't remain thoroughly damp long enough. A thin piece of wood laying on the ground will dry out a fair amount between rains (if you don't live Washington State), and so rot will be slow to set in (though it will eventually). A thicker piece of wood will actually tend to rot a little faster, both because it can't dry out as rapidly and because the weight will place it in closer contact with the soil, leading to more moisture absorption.
Interestingly, they now "mine" cedar. Once it's buried, it stops rotting (as elsewhere said, the oxygen can't get to it, but neither can the bugs). Loggers wander old cedar claims and look for telltale signs of trees that were downed ages ago. Once found, they bring in excavators and claim the trees for shingles, shakes and, possibly, guitar wood (highly prized).I've used yew wood pulled from the mud at the bottom of a water reservoir on Snoqualamy pass in Washington. It's rather prized and has a nice appearance.
On the same note, there's some guys in New Zealand 'mining' ancient Kaori wood and slabbing them out. Some gorgeous stuff, but$$$. Check out http://www.ancientwood.com.Steve