Mold and Mildew Effects on Wood? 1

[StructuralEd]

Are there structural effects on untreated wood by mold and mildew?

Is there an effective means to remove the growths?

 

[COEngineeer]

effective way is dryness. To kill it right away, use bleach and keep it dry after that.

Never, but never question engineer's judgement

 

[Ron]

Yes. Mold and mildew can evolve into "wood destroying organisms", if left without treatment.

The conditions that allow mold growth (high moisture, food supply (the wood))will cause wood to deteriorate at the cellular level. This will, obviously, affect the structural integrity of the wood.

You can remove the mold/mildew with chlorine bleach, but you need to be sure you have stopped any moisture intrusion or accumulation on the wood, as mold and mildew will return.

Check the vapor drive through the wall. Make sure you don't have a vapor barrier in the wrong place. There are lots of myths considering moisture intrusion, vapor drive and permeance of the materials. Even though theoretically materials may be designed to "breathe" and release moisture accumulations, in reality that doesn't work well at all. If water gets into a wall cavity, there is nothing that will drive it back out in any reasonable time frame. It stays and does huge amounts of damage.

 

[StructuralEd]

This would be for an abandoned building with leaks through the roof, wetting the 2 floor levels of framing and obvious moisture issues in the crawlspace.

Other than feeling obvious softness in the wood when probed, what other ways are there to access if the organisms are destroying the material?

 

[Ron]

Check the staining. WDO in an advanced stage will present a black stain. If you still have brown wood color, though wet staining is obvious, just probe with a pick. If you meet resistance with the pick within 1/4 to 1/2 inch, you're probably OK...just clean it and dry it.

If you are showing any white staining in a black background, you probably need to look at replacing the member. That's reasonably advanced.

 

[dik]

Current recommendations for removal of mold and mildew is to use a detergent and not necessarily chlorine bleach. Some molds and mildews produce a toxic byproduct when oxidised.

As noted above, the conditions for mold and mildew is the same to produce 'dry rot', or more correctly brown rot. Moisture conditions upwards of 20% will cause this.

The problem with dry rot is that by the time it is noticed, you may have lost 20-25% of the material strength.

Dik

 

[racookpe1978]

Loss of structural strength is important, but loss of "building useability" (staining, odors, mildew growth inside walls and behind enclosures, mildow and mold growing unchecked near HVAC and attic entrances) are ALSO a money-loser.

Ripping out the bad wood, mildewed inside walls and sheetrock, loss of use of building, allergies and lawsuits due to "loss of diligence in protecting the building from water" .... Those will be expenses coming back across your desk.

In the long run, you can't afford to just paint over the bad wood.

 

[StructuralEd]

Structural restoration is the goal.

 

[SlideRuleEra]

"Inspection of Wood Beams & Trusses"

http://www.wbdg.org/ccb/NAVFAC/OPER/mo111_1.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[dik]

You have to stop all mold and mildew action ASAP; it is progressive deterioration. You have to remove the source of moisture then you have to 'kill' the little beggers.

If it is structure, you have to provide temporary support if required. It is then a matter of reinforcing the damage in a manner that is cosmetically acceptable.

Reinforcing can be done with RFP, epoxied steel dowels, etc.

Dik

 

[StructuralEd]

NAVFAC has some good publications, don't they?

 

[dik]

You might want to try some of the Park agencies. They are involved with restoration. The challenging part is to fix it without affecting the appearance.

Dik

 

[jheidt2543]

Sorry this is so late, but I thought the attached two pictures might be relavent. They are from an inspection I did of the heavy timber roof trusses in an industrial building built in 1910.

Photo #1 Water damage from roof leaks resulted over time in the growth of the "mushrooms" in this picture. The top cord member is a 8x6 and the diagonal is a 8x4 and the large mushroom in the middle is the size of a man's fist!

Photo #2 Shows a technitian using a Resitograph to NDT check the interior integrity of a heavy timber truss member. Basically it is an ordinary hand drill attached to a roll-chart recorder. As the long thin drill bit goes into the wood, the chart recorder graphs the drill resistance which gives a visual printout of the wood condition for the full thickness of the member. Areas of dry-rot have less resistance than solid wood, so the graph line drops.

 

[jheidt2543]

Here's the second photo!

 

[jheidt2543]

Sorry, I tried again, but maybe the photo file was too big at 4.0Mb?

 

[msquared48]

Black mold is toxic as H$%^ and very carcenogenic in nature. Take care when removing it, wearing appropriate respiratory gear. It is VERY prevalent in the Northwest here, inside AND outside.

Mike McCann
MMC Engineering