OK, O’Wiseones:
Can someone that has an experienced eye tell me what I think is mold growth on OSB? This is on the underside of Weyerhaeuser’s Structurwood OSB subflooring and it’s in every bloody place that you look. The house is, get this, less than a year old!
If you look at the attached photos perhaps someone could tell me if they’ve seen this before and if so, what remediation methods were used? I have a sinking feeling that all 30 houses in this subdivision (built over the last 3 years) could be faced with the same problem.
This house in which these photos were taken has an HRV, a High Efficiency Carrier furnace with a continuously operating fan, low humidity levels and is built over a heated, concrete floor crawlspace.
Is this stuff growing? How can you tell if it’s stopped spreading? Who tests for this kind of thing? The home is located in a town in the central part of the Province of British Columbia (Okanagan Valley). The builder of some 40 years is top notch, but a wee bit on the slow side, and is an R-2000 qualified builder as well.
What would you guys do if this was your place or a customer called you up and asked you to come by and “take a look at these black spots, will ya?”
Thanks to all.
Cheers,
Ken
“They don’t build ’em like they used to” And as my Dad always added… “Thank God!”
Replies
The first thing that I would do would be to get a hygrometer and wood moisture meter and see what kinds of moisture levels that you are dealing with.
Looks like a mold or similar fungus to me.
But so little that it is not causing a problem now.
You can wash it off and monitor it to see if it comes back.
Where is this located? Is it even across the floor or near the outside walls or under kitchen or bath areas?
Since this is a "new" house it is possible that there was a big moisture load from the concrete, DW, paint, and lumber and now it is dry enough that it won't grow back after being cleaned.
But moisture testing would help tell you where you are at.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 12/30/2006 12:04 pm by BillHartmann
Thanks, Bill:Moisture levels are actually quite low - 34% in a 72 F house. Spots are uniform in the crawlspace. Don't know what else to look for - spots are even in the same shape and size directly over the furnace, so go figure?Cheers,
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
But that is in the house.Measure the humidity in the crawlspace where the mold is.From the description I get the impression that the crawlspace is sealed, IE, no vents through the foundation to the exterior.What kind of ventalation is there between the crawlspace and the house.Either by open vents, circulation fan, or ducts of the furnace. Note that it needs both supply and discharge or return for the air to circulate..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Ditto what you said. But even if crawl is vented there could be a problem. I'm with you and assume high humidity in the crawl. If crawl has concrete floor, is there vapor barrier under concrete? If not, I would seal concrete floor if it is not and also make sure that if crawl is sealed that it is conditioned. If crawl is not sealed, I would seal and condition.
Also could have been caused by moisture during construction and mold could be dormant now. Use a moisture meter on the wood to check the % moisture in the sub floor. Somebody can correct me if I'm wrong but I believe mold goes dormant below 15%.
I see no reason to be concerned. Mold washes off with soap and water or a bleach solution. It is caused by moisture. Find the source of the moisture and rectify.John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
If the wood is at 34% it can rot and that is a high MC for any wood. The ambient of most wood is around 11% MC depending on the location of course. In AZ it will be much less. Even in San Francisco and near the water it will be around 11%. If the MC is above 20% it will begin to rot. Above 30% it contains free water. I would assume that the sheets when they were manufactured were at or below 6-8% MC.
Yep, I got the message about the moisture content of the wood and I will check it....somehow. Just to clarify though, the humidity that I've been mentioning is the relative humidity of the air in the house and crawlspace as measured with a hygrometer. The OSB, now, is crumbly dry and that is why I'm wondering if the mold has stopped or has slowed its growth. How do I know that the OSB is dry? Well, Mr. HVAC ran the exhaust vent up through the OSB and fitted it so tight that when the pipe expands and contracts the noise in the wall cavity is like a drum. So, I had drill a series of holes around the vent pipe to give it some expansion room. In the process of drilling the OSB I noticed how crumbly it was, not to mention how nicely it went down my shirt and places further South. Grrr!
The worst area seems to be the OSB sat on top of the joists. The attached photo shows the density along that point of intersection in addition to the rust on the screws, which obviously suggests things were pretty darn wet for a spell. The investigation will continue next year!Cheers,
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
If you have rust on screws then obviously there is an excess of moisture/condensation. I have worked on one home where there was actually visible water on the rafter at certain times of the year. during other times of the year the temperature was higher and that was not the case. It was so bad that in their house the windows would sweat badly. What I did was to ventilate the attic space thought eave vents and ridge vents. It solved the problem and allowed their home to heat better. The attic space was so locked in that the moisture trapped in the attic could not escape. Another house I worked on has no attic vents and the house was cold in the winter and hot in the summer. The ventilating area is to be 1/150 of the space ventilated. There must be eave and vents for the upper portion of the roof. (IBC 2003 1203.2) there is also an exception which is listed at 1/300.An explanation is at http://www.iccsafe.org/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=001567
Have a look at these recent papers. The attic venting issue is not that simple. I've worked on 4-5 attics in my 25+ year career where adding attic venting actually increased moisture in the attic and in some, heating bills increased.
See:
http://www.fpl.fs.fed.us/documnts/pdf1999/tenwo99a.pdf
http://www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/MP02-5778.pdf See the conclusions here
http://www.cmhc-schl.gc.ca/en/co/maho/gemare/gemare_001.cfm
Thanks for the information. I have always done what the locals recommended and have never had a problem. Seems to me that moisture problems have been on the increase the past few years around the country. My nephew who lives about 60 miles north of Seattle tell me that the area has new homes which are rotting. I do not have an answer for this but have always wondered if it would be better if plastic were put on the inside and outside of a building underneath the drywall and the siding. I have worked on buildings which had insulation that was damp when it was 90 degrees.
"I do not have an answer for this but have always wondered if it would be better if plastic were put on the inside and outside of a building underneath the drywall and the siding. I have worked on buildings which had insulation that was damp when it was 90 degrees."You may want to do a search here on Persist system. It "seals" on the outside of the framing.But plastic on both the inside and outside of the walls is recipe for disaster.The walls need at least one direction for any moisture to dry back out.And unless you are building Space Lab quality (and $$$$) buildings then at least some part of the year you will either get a little water blown past the flashing and/or a little mositure will get past the moisture barrier and condense. And don't forget in may parts of the country you have moisture drive in both directions over the coarse of a year.It does not have to be much. Say a table spoon of water. Without plastic that little amount of water can easily be absorbed by the sheathing or DW and dry out in a short period of time without causing any problems.But if it is trapped by plastic on both side it will just set them and steam up the bay. 3 months later and you have anothe event. In a few years you have a nice colony of mold and fungus in that wall..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Yep, that's mold. Bleach spray will kill mold. At least it killed the mold I sprayed it on at my house.
Builder being slow could be the problem. I was amazed when Pulte tore down the woods and built a subdivision next to my old house. They would build the foundation, bang out the frame and sheathing, put on roofing felt and move on to the next one. Big storm would come in and rip the hell out of the felt and the inside would get soaked. When I moved there was something like 18 up, a couple finished, one or two more with shingles, the rest just ripped felt and they stayed that way for weeks. I went over once to look around and noticed that most of the interiors had obviously been soaked repeatedly. Glad I'm not living there!
Steve.
I would call the supplier and have them send a Weyerhaeuser Rep out.
Thanks for the comments, guys. I've attached a photo of the crawlspace and by the way, it's almost the same temperature and humidity as the main floor (house is a bungalow) - dry and comfortably warm. Material under the slab is sand and drains water just about instantly, so things are pretty dry in that department. Otherwise, I can't figure out why it's where it is nor if it's growing or not. Tough to tell and I'm not sure that I want to open a hornet's nest and ask too many questions in the neighborhood at this time.
I think I'll call the Weyhauser rep - he's bound to have seen this before. Good suggestion. Cheers,
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
lots of good ideas here,but whatever you do get it cleaned off.i just sold a house that had about 10 spots like that in a 24" space.you could wipe off with your hand,i hadn't ever noticed them or i would of cleaned it.i sold the house iand had to declare mold,what bs.molds been with us forever but it's the new 21st century asbestos panic. larry
hand me the chainsaw, i need to trim the casing just a hair.
Edited 12/30/2006 3:06 pm by alwaysoverbudget
I know things up north are different than on the litigious left coast, but ... You might want to research your local requirements for mold remediation with special emphasis on air quality issues. I have seen six figure arbitrations wherein the homeowners lawyer claimed his clients were forced to move from their home due to airborne mold reactions arising from the improper removal and cleanup of a mold spot that was less than 2 square feet.
watch out... most contractor's liability insurance excludes mold & lead hazards
measure the wood moisture, measure the crawl soil, measure the RH in the crawl....... test , test, test
this mold issue is just crazy.....yet, you do have to be concerned for your own health
losing a lawsuit to mold is detrimental to the health of your companyMike Smith Rhode Island : Design / Build / Repair / Restore
Those look like brown recluse spider egg sacks to me.
That looks like mold to me. To find out if it's growing, I'd wipe some of those little fuzzies off with a damp rag and see how fast they grow back or just photograph with macro lens from a certain distance and then shoot another pic from same spot in a month's time and compare pics.
Your mention of the Okanagan brings back great memories of CMH Heli Skiing where we flew in choppers chartered from Okanagan Helicopters and drank that wonderful sparkling cider that comes from there.
Are you anywhere near Kelowna or Penticton?
Looks like early construction high humidity caused a bit of mould. You can clean and kill mould with a diluted solution of hydrogen peroxide......no chlorine (nasty stuff in an enclosed space and for sensitve people). I don't have guidelines for peroxide but should be available on Web.
Yep, that's what I'm thinking - don't want a 3-alarm response for something that might be easily fixed. I wonder though, what kind of mess could a Home Inspector create if he wrote this in his report? I'll bet ya a hundred bucks the deal would be a dead as Saddam Hussein if prospective purchasers saw that in a report. Even removing the mould and painting over the underside of the subfloor (where the mould is) would certainly cause folks to inquire, wouldn't it? A difficult dilemma. Thanks again to all.Cheers,
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
< painting over the underside of the subfloor >
I'm sure you could develop faux painting techniques that look like Advantech! Tons of videos and tools at HD.
Forrest
Mold needs moisture. It does not look very serious yet. The problem is condensation. The OSB surface is colder than the heated space below and water condensates on the subfloor. The space above is probably heated with forced air that rises to the top leaving your floor colder than the average room temperature. If you had radiant floors then you would not have a problem.
Because you have a heated crawl space then the space above has to be warmer or else you invite condensation. If I were you I would insulate between your joists. You would lose the benefit of the heat rising but your house probably has heat anyway. Keep the crawl space from freezing but turn down the heat. The furnace and the water heater will keep your pipes from freezing.
Looks like your house is actually sealed too tight. From the rusted screws I would imagine that the floor was wet at some point. The house was sealed in and the flooring is now forcing the moisture down in stead of breathing up.
When you clean the mold, do not get any of the bleach solution on any hangers. The bleach will eat through the hangers in under a year. That goes for koist hanger nails as well. Saw a house that had the attic cleaned, all of the plates on the truss webs where paper thin within 12 months.
That is good to know.
Thank you for posting that.
http://www.quittintime.com/
" G@D DAMN IT RICH! CAN YOU PLEASE SHUT the F UP!" Riverfest 2005
Thanks, oake226. Something tells me this stuff is not going to spread anymore as the house has dried out - caulk along baseboards shrinking back and disappearing like all cheap Builder's caulk does. Probably remove a section and keep an eye on it to see if the mould returns or not. I guess the question is...who should fix it and to what standard? If you don't have professionals determine the type of mould, use the proper removal techniques and the correct follow-up, who's to say that it was rectified properly? You can be darn sure that the Builder is going to balk at this. Then what? Threaten with legal action? That sure to get the job done - not. Do it yourself? That won't guarantee it's done right either. So...? We'll get the ball rolling this week and see what happens after the dust settles. Cheers,
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
Hve your builder do it! Then have hime provide an air quality test from a reputable cleaning company ( even better if its not the same one who cleaned it ).
This reduces your liability and gives you proper documentation when you go to transfer title again.
It looks like you have a conditioned crawl space with different floor levels?Looks 1/2" blue board on part of the foundation, and no vapor barrior on the floor...is that what I'm seeing?We stick a dehumidifier in a conditioned crawl as soon as the house is dried in...mold growth stops.If that is a conditioned crawl, it's done in a way I've never seen...but I'm just a SmallTannedSouthGuy<G> Oh God said to Abraham, "Kill me a son"
Abe says, "Man, you must be puttin' me on"
God say, "No." Abe say, "What?"
God say, "You can do what you want Abe, but
The next time you see me comin' you better run"
Well Abe says, "Where do you want this killin' done?"
God says, "Out on Highway 61."
Yep, Snort, things are done differently up here in the Great White North. Foundation walls have 2" SM insulation (R-10) applied to them - only to two feet below grade (I'm adding more now). There's a pit for mechanicals - that's why it looks like two levels. Slab is poured directly on sand that the site is composed of - good drainage. Relative humidity levels are low as the entire crawlspace is conditioned with take-offs from the duct runs.
Funny things happening already: 1) Builder not returning calls 2) Weyerhauser has no comment about the mould on their Structurboard. Kinda figured as much. Sigh.Cheers,
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
Well, that doesn't sound nearly as bad as I was thinking...You're on the right track extending the rigid insulation. I think I'd try and get a good caulk seal between the board and the slab.I also think you're right about the humidity %, the mold you're seeing may be dead...do you run AC up there? Down here, poorly insulated ductwork in a crawl will rain condensation in the summer.I'm betting it was majorly wet when your house was framed (BC gets that way, doesn't it?), and if no new water is getting in the crawl, you're ok.Like some one else mentioned, take pics of certain areas, and see if they grow...or, you could start raising 'shrooms<G> Oh God said to Abraham, "Kill me a son"
Abe says, "Man, you must be puttin' me on"
God say, "No." Abe say, "What?"
God say, "You can do what you want Abe, but
The next time you see me comin' you better run"
Well Abe says, "Where do you want this killin' done?"
God says, "Out on Highway 61."
Instead of just shooting pix as is, perhaps leave some untouched, whack some with bleach, and photograph both for future comparison.
I just bleached out some mold inside a closet at my mom's. So far (a couple weeks) that seems to have done the trick. Also looked behind some paneling, but no mold there, just in the closet.
-- J.S.
Don't worry, Its only those pods from the movie caccoon. Pretty soon you will have seniors swimming in your pool.
Bleach, bleach, bleach