Sand Blast or Soda Blast Attic Mold?
CplDevilDog
| Posted in Construction Techniques on
Opinions? First hand experience?
Hi all,
job is removing mold from underside of roof sheathing and rafters in poorly ventilated attic. Removing all mold infested batts, blasting undersides clean. Vacuum and re-install batts to R-60 with baffles and ridge vent correct. Eave vents will be added during next years re-shingle to increase airflow (no overhangs for vented soffit).
Any opinions or war stories concerning sand or soda blasting? I figure since I am vacuuming the entire space at the end of the job, I can use any type of media? Soda seems very expensive and the equipment is not as available.
Thanks
Replies
Perhaps there's another choice: dry ice.
I saw this on "Holmes on Homes," and it looked like a great idea.
I was wondering about the extra weight of all that media in the attic - but then again I don't know how much media gets shot up there.
Media Weight
We are pulling all of the old insulation prior to blasting. I am hoping we can vacuum up the media every hour or so, screen it and recycle it into the blast pot.
Dry Ice was my first idea as well. I read somewhere that there might be issues with Carbon Dioxide build-up in enclosed spaces and just didn't feel comfortable working with it.
Agreed
that blasting would damage the wood. It sounds nuts, and I can't imagine why you'd try to remove mold that way.
Don't know about the bleach either.
Call a mold remediation company and have them treat the plywood. If you can't live with the stains, replace the plywood.
Wood damage
Also my biggest concern. I spoke with a blasting media rep yesterday and he said one of his customers had used extra fine "Black Beauty" media at about 80PSI to remove the finish from an Oak mantlepiece .
I am hoping to use medium to fine grit at about 90 PSI and keep the nozzle moving quickly enough to avoid etching the wood.
If I have to I'll switch to corn cob or black walnut shells as the media.
I agree with the others -- blasting away the discoloration may be "out of sight, out of mind", but is misdirected. If the discoloration really is due to mold (not clear from the picture) then it should be treated with an appropriate chemical. Blasting it will just spread the stuff around and (further) damage the wood.
Lessons learned
Ended up going with Black Beauty medium grit at 125 PSI with a .25" nozzle. We used 1500 pounds in two days to do 1200 SF of sheathing. Another 2 days to clean out all of the media! Couple of things learned.
1) Don't allow the blast nozzle to drop even after the deadman switch has been released, even a few grains of media left in the hose will eat right through ceiling drywall in nothing flat.
2) If your State requires OSHA safety valves on rental compressors, remove it.
3) Air seal EVERYTHING before you start. Special focus on top plate penetrations and bath vents
4) Rent a shop vac for the clean up, even with frequent filter changes the volume was to much for our 6.5HP.
5) The finer grade of Black Beauty might leave the rafters a little less hairy.
6) We used a 300lb Blast Pot, it required refilling every 30 minutes or so. Go with the 600 if you can
7) Don't leave your fancy touch screen phone in your pants pocket! That media is SHARP!
best way to treat mold in your attic
There is a much better method and product. It is called BORACARE. It can ONLY be used on bare wood so if your wood has any paint or stain, it will not work. Treated lumber is fine as long as it has dried out (one month per inch of thickness unless it is kiln dried treated lumber). Boracare comes in one gallon containers and is not cheap, but it is mixed with water and one gallon will probably be more than enough for you to use. I paid around $160.00 per gallon for it to treat my father's home after Hurricane Katrina for mold infestation.
It is a very thick substance. If you mix it at 4:1 ratio, it will kill the mold and work as a mild preservative. If you mix it at a 2:1 ratio, not oly will it kill the mold, it wil prevent mold from coming back for up to 10 years, as well as portect the wood from any rot, moisture damage and termites won't eat it. It really is a great product.
You will need to use a good sprayer and mix it with hot water to help it to mix. You will also need to clean your sprayer real well afterwards, or it won't work the next time you try to use it. All you do is spray and you are done.
It's also great for treating wood posts that you are putting in the ground to protect it from rot and decay.
Good luck.