August 25, 2011

So you are dealing with a remodel and you find mold. What makes this different from every other time you ripped out moldy lumber?

I know the story. You go to the lumber yard and pick out all that beautiful framing lumber with the black speckled discoloration on it. This mold will be present on about one in every ten boards, unless they keep there lumber outside, like most of our lumber yards, and then the numbers jump to one in every four boards. You build the home with this lumber, it is inspected by the building department and you pass on your final. No one ever commented on the mold and it is just like any other home built today. It is built with pre-existing mold!

Now you start your demolition of a 20 year old house down the street. You find a similar discoloration on the lumber you are pulling out, or maybe even leaving in place. So what makes this moldy wood different from the lumber you just used on the previous home? Should you consult a mold professional?

Well it depends on certain factors. When you find moldy lumber you need to look at it like a detective.

1. Is the discoloration the result of a pipe burst/water intrusion? If yes, then how long ago has this occurred?

In most cases, if water has been wetting lumber, especially gypsum board, for more than a week, you will most likely have mold. Mold comes in many colors and patterns, and grows in many conditions. One thing is certain — it always needs water. There are times that you will see wood discolorations due to water damage that are not mold, though more cases than not you will find hidden mold in wall cavities and on other building materials. Other common locations from mold are under sink bases, on the roof sheathing near the eaves, and on the perimeter crawlspace framing, bottom side of the subfloor and floor joists

2. Is the “mold” or discoloration thick in a given area? Do adjacent framing members have a similar discoloration on them?

If one out of every five floor joists have sporadic discoloration, then it could be just pre-construction mold from moldy lumber. But if the plywood subfloor (plywood typically does not come moldy) or any more than three floor joists and the connecting rim joist in an area have the same discoloration, then contact a professional like us because you have mold! If your job is in the Lake Tahoe basin or Truckee area in most cases we will give you free advise!

3. Is there proper ventilation in the affected areas?

You know the ratios, although it is not always sufficient to go off what the building department requires for ventilation. It takes some common sense.

  • Cross ventilation in crawlspaces. If you put all your required ventilation on one side of the house, how do you expect the crawlspace to breathe? I know if it is a sloped lot and you have nowhere to put your vents, then this is where you need to show your value as a quality builder. You need to design or find someone to design a mechanical ventilation system. You can use PVC or ductwork with vents on the uphill slope that can exhaust stale crawlspace air and help pull air in from the downslope side. Many of your heating contractors can come up with a solution to this issue. Feel free to contact Tahoe Mold and Water, Inc. for an estimate for ventilation of a crawlspace.
  • Attic Ventilation? HA! HA! There are a lot of contractors drilling holes in eaves, installing gable vents and even putting in ridge vents, although they still haven’t solved the ventilation problem. “Why?” you ask. Because they don’t supervise their insulation installer. The majority of the attics having mold and ventilation issues also have eave block vents. The issue is that they are all blocked by the insulation. To prevent this, you should have your insulation installer insert baffles to keep the insulation from blocking the ventilation. After you are complete with construction you should do periodic inspections of the attic to confirm ventilation is sufficient.
  • Ceilings with rafter construction, like attics, require ventilation. Where I tend to see the most prevalent issues are in these systems that have long runs of 2x12” rafters with their cavities totally stuffed with 12” fiberglass batt insulation. In some cases a system like this will get so water logged from vapor build up that it causes the ceiling to drop from its own weight. Eave vents as well as ridge vents should be a priority with this kind of structure. Also, you should use high density fiberglass batts that will get you the required R-value and allow for a small ventilation channel between the insulation and roof plywood. Again, you should also install baffles to keep the insulation from blocking these air channels and make sure that there are no other blocks in the rafter run.

So if you find a home that you suspect of mold growth, and it has some of the above issues, please give us a call. We especially enjoy working with builders and industry professionals that want to put out the best product possible. We can provide you a free estimate and will work with you to get the mold taken care of promptly so you can continue on with you project having peace of mind that you did things right.

Call the owner, Ned Riley, direct at 530-448-6494 or e-mail If you have a water emergency or need us to get on something ASAP, please call our 24-hour emergency call center at 888-583-MOLD (6653).

Tip of the month
Easy on the Bleach!
Yes, bleach can be an effective mold cleaner on hard surfaces. (Please follow the directions on the bottle for proper dilution) It is not intended to be sprayed at wood framing in hopes of killing mold. This is ineffective and dangerous. Yes it turns the wood white, though the mold is still there. The only way to get rid of mold is to remove it. This should only be done by professionals using engineering controls and hepa filters.
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P.O. Box 5187, Tahoe City, CA 96145
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