Wood decay/insect damage
Wood decay/insect damage
(OP)
Does anyone know of any references that give guidelines on how to determine the length of time that lumber has been rotting or how long it has been infested by termites/carpenter ants? For insurance investigations, it is often necessary to establish an approximate time frame as to when damage first began, but I haven't been able to come up with much information. I've heard some rules of thumb (a well established colony of termites will destroy X board feet of lumber per year), but haven't seen any write-ups.






RE: Wood decay/insect damage
Based on my experience (yes, my own home. and yes I did have a termite inspection!) of severe termite infestation, I found that it was generally reported that termites will destroy about 2" per year of lumber. I suspect that number really depends on the size of the termite colony and as time goes on and without deterrents the colony will increase as will the damage to the residence.
RE: Wood decay/insect damage
The rate of deterioration generally depends on the extractives within the wood (these vary with the species and can vary within a species depending on whether the tree grew on the north or south side of a hill, in the same vicinity), the moisture content (climate conditiions) and the type of brown rot fungus involved.
The deterioration is dependent on the type of species, density, growing conditions, and numerous other items.
The damage is named brown rot because the particular types of fungus attack the cellulose of the wood and leave the lignin, giving the damaged material a brown colour. There are several types of fungus that do this type of damage; some are more agressive than others.
All of the fungi that I'm aware of require moisture and there is a threshold of 18% to 30% where the fungi are active. Some literature indicates that the threshold starts at 22%. I think the 22% value is more correct, but when checking buildings with a moisture meter, I use 18% as a threshold (10-12% is a common moisture content and well below the threshold).
Most of the fungi have the ability to 'wick' water via small 'tubes' within their structure. This permits the deterioration to occur a distance of a couple of inches from the actual water source.
The deterioration is also progressive. If sufficient moisture for brown rot to occur is present this year and not for the next 10 years, the fungi becomes dormant, only to continue when conditions are favourable.
Timber can lose 20% of its strength due to rot that isn't apparent. When it becomes visible, the loss is greater (cellulose walls provide the significant tensile strength).
The Encyclopedia of Wood is an excellent general reference, I think the publisher is Stirling, from New York (will check when I get to the office).
RE: Wood decay/insect damage
RE: Wood decay/insect damage
http://www.ianr.unl.edu/pubs/Insects/g1062.htm
RE: Wood decay/insect damage
http://www.ianr.unl.edu/pubs/Insects
you can find about a bunch of pests...
RE: Wood decay/insect damage
The time for damage depends on the type of fungus... I will try to dig up the name of one that did significant damage in only a few months! I wasn't involved in the project, and only glanced at the file in preparation for another report.
RE: Wood decay/insect damage
RE: Wood decay/insect damage
Correction to my earlier post...
Greatest decay occurs when moisture content is above fibre saturation point (30% +/-)
and continues as long as air is present.
RE: Wood decay/insect damage
Forgive me, I know this is not exactly dealing with the subject, but next time try to use light gauge steel instead of wood framing in termite infested areas. Your clients will be delighted.
idl@istar.ca
www.givmorehomes.com