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WILL1E
Moderator
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# Posted: 29 Aug 2022 01:44pm
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So as i was cleaning out the underside of my cabin this weekend (cabin is elevated 1-2' off of sloped gravel ground) and noticed something....it looks like my untreated joist are getting discolored with what i can only assume is mold. I forgot to snap a picture. My rim joist are treated but all my joists inside that box are untreated including the blocking. My built up beams are also treated.
Nothing is insulated under there and with the 1-2' gap i thought i was getting enough airflow through there. The ground is slightly slopped and i've never seen standing water under there.
#1 What can i do to stop, prevent and/or remedy what's already on the joists?
#2 What can i do to improve the situation going forward under there?
This is an old picture from when i started building last fall, it's just to give you an idea of how much space i have under the cabin.
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WILL1E
Moderator
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# Posted: 29 Aug 2022 01:47pm - Edited by: WILL1E
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A further out shot to show the slope below the cabin...roughly 5" over 16'
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Brettny
Member
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# Posted: 29 Aug 2022 02:35pm
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Oil based stain may help future but are you sure its actualy mold? Can you get a few pictures?
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WILL1E
Moderator
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# Posted: 29 Aug 2022 02:41pm
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Ill try to snap some pictures next weekend. I know it's not dirt. It's like black spots. I see it at lumber yards sometime in between boards that have been bundled outside for awhile.
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paulz
Member
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# Posted: 29 Aug 2022 06:28pm
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Maybe all the extra materials under there inhibited the airflow. Mine is just like yours, non PT joists, no mold.
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travellerw
Member
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# Posted: 29 Aug 2022 06:58pm
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No mold under mine and its built over grass (that I just let die). I also have materials stored. Maybe your humidity is just really high.
There are good penetrating stains you can apply.
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gcrank1
Member
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# Posted: 29 Aug 2022 08:18pm
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Garden sprayer with a bleach solution?
Do remember correctly that when you had built the deck you covered it with a tarp during a rainy bit?
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darz5150
Member
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# Posted: 29 Aug 2022 08:28pm
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Quoting: gcrank1 Garden sprayer with a bleach solution?
Yep.
Then I would also mix up some 20 mule team Borax in warm water till it dissolves well. Then spray that on it too. Its a cheap bug deterent.
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spencerin
Member
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# Posted: 29 Aug 2022 09:11pm - Edited by: spencerin
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After you clean up the mold, I would paint the untreated wood with something like WOODLIFE CopperCoat.
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travellerw
Member
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# Posted: 29 Aug 2022 10:32pm
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Quoting: darz5150 Yep. Then I would also mix up some 20 mule team Borax in warm water till it dissolves well. Then spray that on it too. Its a cheap bug deterent.
Borax is the best mold killer there is. Its all that was used down in the Caribbean. One application could keep mold off the walls for close to a year. However, unlike bleach it doesn't make it disappear. You need to scrub the mold off.
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Brettny
Member
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# Posted: 30 Aug 2022 05:19am
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Quoting: gcrank1 Garden sprayer with a bleach solution?
Bleach dosnt kill mold on porous surfaces. White vinegar does though.
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toyota_mdt_tech
Member
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# Posted: 30 Aug 2022 08:02am
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I'd say a black non breathable vapor barrier on the ground below it or a breathable vapor barrier tacked to the underside. If you decide to skirt it, do the black barrier on the ground and add vents in the skirting
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WILL1E
Moderator
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# Posted: 30 Aug 2022 08:32am
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I know it wasn't there (visibly) in spring when i was under there. And yes, it's been wet and humid up there this year so i'm sure that hasn't helped anything.
What about painting over it with some like Kilz? Would that be something to stop the mold and protect it from happening again?
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Brettny
Member
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# Posted: 30 Aug 2022 09:11am
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You need to kill it first. Not killing it could just push it upto the living area. Do you leave windows open upstairs for good ventilation when your not there?
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paulz
Member
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# Posted: 30 Aug 2022 09:16am
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Quoting: gcrank1 Garden sprayer with a bleach solution?
I was thinking about that.. sounds like fun.
Maybe a sprinkler nailed to a piece of plywood, drug through by a garden hose..
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travellerw
Member
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# Posted: 30 Aug 2022 09:46am
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Quoting: Brettny You need to kill it first. Not killing it could just push it upto the living area. Do you leave windows open upstairs for good ventilation when your not there?
I agree, you need to kill it first, then treat. I would do a borax solution in a garden sprayer. Wait a week or so, then come back and apply a protection. I'm not a fan of paints or primers as they don't let the wood breath. I think you are better off with a good penetrating oil stain. It should last for years under there.
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WILL1E
Moderator
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# Posted: 30 Aug 2022 02:54pm
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No we don't leave any windows open. With the 10' walls and minimal soffits i was worried about rain getting in and the security risk.
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travellerw
Member
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# Posted: 30 Aug 2022 09:43pm
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Quoting: WILL1E No we don't leave any windows open. With the 10' walls and minimal soffits i was worried about rain getting in and the security risk.
Do you have Internet out there? I just made one of my windows automated with a linear actuator. It would be very easy to connect it to the internet so you could open it whenever you want (or even on a timer). That is my plan eventually.
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NorthRick
Member
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# Posted: 31 Aug 2022 05:34pm
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Quoting: WILL1E No we don't leave any windows open. With the 10' walls and minimal soffits i was worried about rain getting in and the security risk.
Open or closed windows won't have any affect on mold growing on joists that are not in the interior of the cabin. If it were me, I'd spray the joists with a borax solution and focus on getting water runoff going away from the cabin.
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gcrank1
Member
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# Posted: 31 Aug 2022 08:47pm
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Of the mold started in the initial deck building from damp lumber and humid conditions (and maybe covering it all with a tarp for a while?) all you would be dealing with now is clearing that up, not a continuing issue.
Of course, keeping dripline spash away from underneath is important now.
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toyota_mdt_tech
Member
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# Posted: 5 Sep 2022 01:26pm
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You can by wood preserve in a spray can, if you can fit under there, treat them.
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paulz
Member
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# Posted: 5 Sep 2022 05:47pm
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I was just at Harbor Freight, using my 25% off Labor Day coupon. They had a lithium powered chemical sprayer, for $39, fairly small, maybe a foot tall. I was going to get it but the coupon wasn't usable on that brand. Also, I have nothing to spray.. so I got a big tarp instead.
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WILL1E
Moderator
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# Posted: 17 Oct 2022 03:42pm
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I was under the cabin this weekend installing the 3rd beam and snapped a few photos of the suspected mold on the untreated joist. What do you ya'll think? And given the rapidly approaching winter here in WI, do i just leave it till spring or should i take some action now?
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FishHog
Member
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# Posted: 17 Oct 2022 07:45pm
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Me personally, I wouldn't give that a second thought. People have built with untreated wood for many centuries more than they have with treated wood. I'm not sure that is even mold and if it is, I suspect it was from when the wood was still wet and looks good and dry now and shouldn't be getting any worse.
Maybe its just me, but that wouldn't have made me even raise an eyebrow.
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Brettny
Member
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# Posted: 17 Oct 2022 08:51pm
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Just spray it heavily with white vinegar. You wont see it again. That's so open under it I doubt it came from after the sub floor was even on. Did your lumber yard store the wood outside?
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travellerw
Member
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# Posted: 17 Oct 2022 08:53pm - Edited by: travellerw
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Yup I agree with FishHog.... I'm not sure that is mold. Could be the sap oxidizing...
Rub your finger across it and then sniff. Black mold has a very distinctive smell (and not like bread mold). Its a pungent stick in the back of the throat kinda smell..
In any case, no matter what you decide, pretty sure you are fine till next spring.
P.S. I feel sorry for you lifting that beam on your back on those rocks... Yikes, that can't be comfortable.
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gcrank1
Member
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# Posted: 17 Oct 2022 09:29pm
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Oh No!
You gotta tear it all down, replace those and Start Over
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Brettny
Member
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# Posted: 18 Oct 2022 05:09am
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The fact that you can see the lumber strap in the mold tells alot. That's lumber that was wet in the stack. If it was wet after the stack the strap would be visible.
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WILL1E
Moderator
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# Posted: 18 Oct 2022 08:23am
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Whew, thanks for the reassurance fellas, i was getting worried here.
When i was under there this weekend, i dug down below the gravel and it was bone dry. mind you it's been pretty wet up there the last week or two. I've never had standing water or snow under there. So if the soil is wet, it's at least a couple inches down.
Brettny, i'm glad you called that out. I thought that was suspicious as well. All the untreated joists is from Home Depot if i recall correctly...bought those when there was still some lumber shortages. Regardless, home depot or menards, both sell it inside or in a covered area.....where it was before that is anyones guess.
gcrank1...your a funny fella aren't ya?! There wouldn't be any tearing down, she'll go up in flames before that happens!
Travellerw....like i said, it was my punishment for being a cheapskate when i started. A few sore spots on hips and ribs but not to bad.
I forgot my little floor jack so next time i go up i'll add a little more pressure to the beam and get the bases adjusted. I'll then add the hurricane straps to keep the beam in place.
I bought Borax to mix with water in a sprayer...would bleach be the better route if i'm going to do it?
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Brettny
Member
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# Posted: 18 Oct 2022 09:01am
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Look up how to kill mold on porous surfaces. Borax is for bugs and bleach is for non porous surfaces.
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