Help - Losing sleep over new construction problem

[Janedoe]

My question is going to seem stupid, but I need to ask anyway because I think that we badly botched our new garage.

I'll try to keep my description brief. We roughed in our new 24x30 attached garage last August. It was not roofed immediately because the roofer we'd signed a contract with wouldn't roof the garage separately from the house, and the house was being renovated and wasn't ready for a roof. For the first 3 weeks we had nothing protecting the roof. Then the contractor finally put up a 15# roofing felt. We had torrential rain from mid September to mid October. So much rain that we had flooding - very unusual for the Washington DC area. A few months later, the roofing felt began to rip off, so we covered a portion of the roof with a tarp. The space was dried in by mid January, when the shingles, siding, and garage door were installed. I asked the roofing contractor a few times, before the shingles were installed, whether we should replace the OSB on the roof and walls before shingling and siding, and he said "no, it's fine." He said that it was fine because he didn't see swollen areas.

Now I'm seeing spots of mold on the wall and ceiling OSB. We've insulated the walls but not yet put up the drywall. The ceiling OSB is still exposed. I'm concerned that the mold will get worse with time once we finish the space. Especially since the garage is an unconditioned space. Plus the upper level of the garage will be a master bathroom, condensation and all, and a closet.

When I spoke to our roofer, he said that the mold occurred because of condensation. He said the condensation formed because garages are on slabs, so the floors are cold and the air is hot because it's Summer. Except that I started seeing mold stains last April.

My question is, should we have replaced all of the OSB before roofing and siding the garage?

And if anyone knows about mold, should I expect the problem to continue to get worse without treatment? And does anyone know whether disinfection and sealing works? I can't see whether the mold is inside the OSB, or on its outside surface below the shingles and siding.

Final note, our roofer has been doing whole house renovations for 30 years - I thought we could trust him.

Please give me your thoughts...

Thanks, Jane

 

[1948]

as long as it stays dry, the mold shouldnt be able to grow. just put a mask on and clean off the mold, spray it down with bleach. there should be roofing vents esp if youre going to be using that space. keep the air moving, and also you can buy a dehumidifier. people freak out about mold way to much, plus its mostly a problem when its in your home, not so much a garage. relax, have a cold brew, have your wife give you a back massage. lol

 

[wnstwolf]

Go to your local paint supplier or on line and look for a product called Shockwave. We had 500 year flood here last year and for 6 months I ran a church group that helped flood victims. You spray this stuff on and it will kill the mold and not allow more to come back, Bleach I am told will only treat the stuff you see not prevent more to grom. Shockwave is what FEMA and the DOH were telling us to use but aside from that I can say the stuff worked! It is about $25 buck a gallon but the gallon will make 500 gallons of mix or so.

Like 1948 stated it is fixible.

 

[green.bubbly]

I agree, the mold can be fixed but I would get up on the roof and make sure none of that OSB has any soft spots. I am a fan of OSB but it does not like getting wet for an extended period of time.

Replacing the OSB would not set you back that much money and if it is something that may eat at you for the next 15 years, I would certainly consider replacing it if there is any doubt about its condition.

 

[RustFarmer]

He said that it was fine because he didn't see swollen areas.

I Agree that if the OSB was not swollen it did not need to be replaced.

Mold problems in buildings are due to water infiltration and uncontrolled humidity, not the presence of mold spores. Mold spores are always present in the air.

Mold will not grow if humidity is controlled. Therefore, in buildings, you want to control humidity, both within rooms, and inside walls that make those rooms.

Humidity is controlled in the bathroom by HVAC, a fan, and a window.

Humidity in the garage is controlled by having the door closed during rainstorms.

Humidity within walls and attics is controlled by venting, leak proof construction, vapor barriers, and good design.

Now that your garage addition is weather tight, buy or rent some dehumidifiers and dry it out. You could spray the visible mold with some diluted bleach or Lysol.

It would be impossible to build a wall or attic space that does not contain a single mold spore. The key is to stop water infiltration, and manage humidity through ventilation, so the mold does not reproduce.

 

[brownbagg]

you should of called another roofer, never leave anything to the weather if you can help it

 

[Janedoe]

Thanks!!! How perfect that you have had this kind of experience! Exactly the info that I need.

 

[Janedoe]

But the roof is shingled now, wouldn't I have to remove the shingles to replace the OSB? Which would mean paying for roofing again. And then there's the siding that's already on. I'd need to take it down to replace the wall OSB too, right?

 

[Cryptic1911]

did they use actual plain OSB on the roof, or was it something like advantech? Real OSB gets puffy when it stays wet.. advantech or a product like it is made to deal with moisture better

 

[Steevo]

Dry mold is dormant mold, and as stated above, it is everywhere. As long as it stays dry it won't grow or spread. If you get high humidity or wetness in that OSB any time in the future, it will come back to life when the spores get a drink.
Bleach DOES NOT kill mold. It will kill the mold "flowers", but not the roots, which are deep in the material. This is why mold will re-appear in grout after a while when cleaned off with bleach. Boric acid will kill mold roots, but the wood or other host material has to be soaked with a solution to penetrate deep enough to get to all of it.
As long as it stays dry, there should be no issue.

 

[ddawg16]

Do you have a vent for the roof? Based on my experience with my garage, yea, you can get high humidity up in the rafters.....the inside roof of my garage will actually rain under certain conditions....not worried about mold because I painted the inside....but there is still a lot of humidity up there.

What are you doing for venting? Rideg vent?

 

[kyles974]

put dehimidfier in there, best way to kill mold.....it will be fine
....live in Florida where mold is more common and have done great amount of research

 

[sparelman]

I have a mold problem from a leaky pipe that sprayed water on floor joists in our crawl space for an unknown length of time( pretty nasty looking). I am going to use one of two products that I have heard good things about. One is zymeaway (online at www.zymeaway.com) and the other being Concrobium Mold Control (home depot). Haven't gotten to the point to get them, but will be working on it in the next month. Will let you know which one I use and the results.

 

[barks]

"He said the condensation formed because garages are on slabs," This information needs to quickly be sent to the majority of homes and garages built in the past couple of years that were done on slabs. And, should have used plywood rather than OSB anyway.

 

[KMR Construction]

I hate OSB, soakes up the water and can't be left out. I prefer advantech & cdx plywood

 

[green.bubbly]

But the roof is shingled now, wouldn't I have to remove the shingles to replace the OSB? Which would mean paying for roofing again. And then there's the siding that's already on. I'd need to take it down to replace the wall OSB too, right?

Sorry, I missed that part.

Just want to stress that I was not suggesting that it had to be replaced. Only suggesting that if it would keep you up at night for the next 10 years then it might be worth spending the money for peace of mind.