Mold on Plywood Sheeting in Attic


  #1  
Old 10-30-01, 05:41 PM
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Angry

Our house is 7 years old. This weekend I was up in the attic pulling some wire. I noticed a sort of black mold on the plywood sheeting. It was only on the North side of the house in the middle. The attic is truss construction with bird blocks that allow air in and a ridge vent for ventillation. The insulation is blown in and rest on the ceiling below. The roof is a 7/12 pitch.

When I touched the plywood that had blackened, it felt damp. There was no running water so it does not look like a leaky roof. It is the plywood that is down from the ridge vent and the plywood above is not damage so again it does not look like a leaky roof. As it is on the North side of the house only and frost is usually on the roof for most of the day, could this be some kind of condensation issue and if so, what can I do to alleviate it? Is there a way to get rid of the mold on the plywood?

Thank-you
 
  #2  
Old 11-01-01, 05:41 AM
ssm
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It sounds like some sort of condensation, whats directly below the area in question? A bathroom or kitcken maybe? Do you have any HVAC supply lines running through the attic? Whatever the case may be it sounds like either cold a/c air is hitting the plywood in the summer, or heat is making its way up to the attic in the wintter. To get rid of the mold I would spray it bleach.
 
  #3  
Old 11-04-01, 09:15 AM
Insulman
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I agree with the last post...
Mix bleach with water 50/50 in a spray bottle and spray the area that will kill the mold..

My best guess is that you bathroom exhaust fan is the culprit..

It should be venting to the ridge vent. If it is not you can replace the existing vent tubing with new, and when installing create a elbow in the tubing by going up about two feet back down around 6 inches and then up to the ridge vent. This will stop any mosture build up in the tubing from running back down through the fan as it will accumlate in the elbow and evaporate out on its own..

do you have soffit vents or just gable end vents and the ridge vent?

Good Luck

Jim
 
  #4  
Old 11-11-01, 06:06 AM
R
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The staining on the plywood does not sound to me as mold, rather it is the discloration of the wood when it gets wet and is the prelude to dry rot. The previous replies were correct when pointing out there must be a source for the staining. The easiest way of determining where it's coming from is to take a string with a weight on one end and hold the other end in the center of the stain and let the weighted end hang just above the floor in the attic. If there is a exhaust duct or a heating duct under the weight, then that's your source. If it's a pull down folding stair case, whole house fan louver, recess light, electrical wires and quite a few more, then you're experiencing what is known as the attic-bypass phenomea. This where heat bypasses your insulation, thereby reducing the effectiveness of the insulation dramatically. Let's say the source is electrical wires run into the attic from the rooms below. One clear sign is the discoloration of the insulation. The insulation acts as an air filter and captures the dust in the heated air causing the insulation to discolor. Solution, plug up the hole where the wires go through. Let's say it's the folding stair case, it doesn't close tightly enough. Heated air passes the sides of the panel leaving dust around the perimeter of the opening. Solution, put a latch on pull down stairs to make it tight when it closes. Not only will you eliminate the source of the staining but you'll also save a good deal on your heating cost. If you would like to know more about the concern with insulation, click on the little red house icon at the bottom of this message and read topics "Insulation", "Thermal Boundary", Air Boundary" and "Ventilation".
 
  #5  
Old 11-17-01, 08:43 PM
some help
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Hello
Take a sample to the health departmen and find out what you are working with then you can do what is right new lumber has moisture in it and as it drys things happen, nothing to do with how the house was built or the condition....best to find out....Good Luck
 
  #6  
Old 11-19-01, 05:09 PM
rbisys
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Greetings,

I am an insulation contractor and I agree with the previous advice. But, I run into one other problem that could cause your problem, or aggravate it.

The ridge and soffit vent system is the best, HOWEVER, I see too many systems improperly installed.

Check to see that roofing paper is not covering the ridge vent slot. This slot should be 1 1/2" to 2" wide.

Check on the amount of openings at the soffit. Should be 1 1/2 " to 2" wide slot with 1/8" mesh wire or if aluminum check the type of perforations. Dimpled is 7 1/2 sq in / sf. The hole type is 15" /sf. You need min 15" si per running foot.

Thank you for considering my opinion.
 
  #7  
Old 11-02-11, 12:58 PM
C
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Agree with resercom

I have been trying to convince my wife of the same. It's not mold. It's some discoloration on the plywood after getting wed. We enclosed our carport about 9 years ago. This past August my wife decided we need to construct a new carport. That entailed ripping away some of the existing structure of the old carport, as the new carport will be connected to the existing structure. Well a storm came along and some of the exposed plywood in the attic got wet. Of course, it became discolored and stained. But it's not mold. Well telling her that did not suffice. She has had the whole ceiling torn down and we are in the process of replacing it. Even if it was mold, all we had to do was replace those pieces of plywood that were suspect. They(wives) just will not listen sometimes.
 
 

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