This may be a long story.....but I think it requires some history...sorry in advance!
I have an older home built in 1900. It has a fieldstone/brick foundation and a concrete floor. About 30-40 years ago a 13'x12' addition was added to the side of the house with a concrete block foundation. There is a 2'x2' hole in the brick foundation to allow access to the crawlspace.
When we bought the house 5+ years ago the building inspector told us to put a vapor barrier over the soil in the crawlspace to reduce humidity in the basement. Shortly after we bought the house that is exactly what I did.
Way back then we had some water issues in the basement. There were no gutters and the soil around the addition sloped toward the concrete block wall. During some heavy rains we got some water in the basement. Nothing major, just some seepage through a few places in the foundation. I'm sure the soil under the crawlspace got wet as well.
We installed gutters and improved the slope of the soil around the foundation. For the past 3+ years the basement has been bone dry.
Okay....fast forward to today.
I am trying to improve the insulation in the basement as it gets rather cold down there during the winter. Alot of the cold air comes from the crawlspace access hole. The room above the crawlspace also has really cold floors so I wanted to add some insulation between the floor joists. I will also be adding some rigid foam insulation against the concrete block wall in the crawlspace.
Uh-Oh...PROBLEM!!!
The job itself was misserable since there is only about 2ft of height to work with in there. But when I was finished and inspected my work I found.... MOLD!!!
Okay... I look a bit deeper into it. The mold is underneath the plastic sheathing I put down. Apparently there was already some sort of an attempt at a vapor barrier in there. It had a tar-like coating on the soil side and the top side was more like papery-cardboard. The mold is on the topside of the old vapor barrier in between the plastic sheathing. Duh...moisture + paper + time = MOLD!!!
No good deed goes unpunished I guess. I didn't even realize it was there when I did it 5 years ago. Ooooops....what these young kids do...
So. I plan to remove the plastic sheathing and then remove the old vapor barrier. But what then? I imagine the soil has alot of organic matter in it from the past 40 years. Should I then install new plastic sheathing? If I do will the soil get moldy?
Should I leave the dirt exposed? As far as I can tell it is dry in there and all the water drains away from it.
THanks! And sorry for the long winded post!
What do you mean when you say As far as I can tell it is dry in there and all the water drains away from it. ?
Is water entering the crawl space? If it is, the outer wall has to be sealed from the outside before anything else is done. That might be all that's needed. Then nothing needs to go on top of the dirt.
Sorry...its late and I should have clarified. Now that we fixed the soil slope issues and installed gutters, all of the rain water drains away from the addition. I don't see any easy way for water to go in. The soil seems dry in the crawlspace.
Everything I read says a plastic vapor barrier over the soil is a good idea. I dunno...since there are no drainage issues or obvious ways for water to get in....it seems best just to let it breath.
Thats what I'm trying to figure out. Leave it as bare dirt or cover it with plastic again. (this time without the old cardboard paper in between)
I'd leave it for now. Besides, you don't want to go back in there anyway.
I'd leave it for now. Besides, you don't want to go back in there anyway.
Well the plastic vapor barrier that is in there and the moldy barrier beneath it is coming out. If putting a new barrier on top of the bare soil is the best thing to do...I'm okay with it while I'm in there. If leaving the soil bare and letting it breath is a good thing to do...I'm okay with that also.
Just trying to figure it all out.
I would remove the old barrier leave it.
Is there any ventilation in the crawlspace? I don't know much about it but from what I've read, if you put down plastic and the crawlspace is unvented - you need to run a humidifier.
Crawlspace is connected to the basement via a 2'x2' access hole that is open. There are vents in the sides of the crawlspace for outside air but I have sealed them up.
In my climate 90%+ humidity during the night is the norm, they would do more harm then good. If left open the entire basement gets humid.
There is a dehumidifier in the main part of the basement. The basement stays in the 40-50% humidity range.
I think you are supposed to run a dehumidifier in the crawlspace if the vents are sealed. I'd be inclined to open up the vents and make sure there is a good seal where the opening to the crawlspace is.
Hmmmm. I don't think I could seal the opening to the crawlspace 100% because the steam pipes and electrical run through that opening.
Another thing that concerns me is that if I seal the access hole and leave the crawlspace foundation vents open...the humidity will always be between 50-95% (outside humidity) in the crawlspace.
Maybe it's time to buy another dehumidifier
perhaps.....but the one that is in there now keeps the basement below 50%. I haven't checked the humidity level inside the crawlspace....but since the opening for it is 5 feet from the dehumidifier, I can't imagine it being drastically different.
I'm more concerned about on what to do with the bare dirt floor in the crawlspace after I remove the moldy vapor barrier sandwich.
Put plastic down as a vapor barrier over the dirt, running it up the walls a foot or so and taping all the seams and the junction with the wall.
Thanks for your help guys! After some more inspection last night it seems the problem is a little worse than I thought. There is a little mold on the ceiling of the main part of the basement, but only around the perimeter. The mold is located on the 6x6 sill, joists and bottom side of the floor boards around the perimeter. It is a little worse adjacent to crawlspace room
I don't know why this happened now and not in the 113 years the house was built prior to this. I've made many steps to reduce humidity and moisture in the basement. My only guess is that it is from mold spores that spread from the crawl space.
I have balloon construction, and I'm 90% sure the walls are un-insulated. I only prey that the wall cavities aren't covered with fuzz.
My plan:
1. Short term solution: Spray the infected sills, joists, and floor boards with bleach just to kill whats on the surface.
2. Take the crawlspace's original moldy vapor barrier and the plastic thats on top of it out.
3. Spray the soil and concrete walls inside the crawlspace with some Foster's 40-80 disinfectant for good measure. Let it dry overnight or so.
4. Install a new vapor barrier...a solid sheet of 10mil or greater plastic. Caulk and tape the plastic to the concrete walls to seal out the soil below as well as possible.
5. Spray the sills, joists and floor boards that were infected in the main part of the basement with Foster's 40-80.
6. Spray those areas again with a protectant like Foster's 40-51 clear encapsulant.
7. Insulate the joist bays that are adjacent to the sill with R-19.
Maybe invest in a bigger dehumidifier and put it next to the crawlspace opening.
UGH!!!!!!!
I created a thread earlier about mold in my crawlspace and determined I need to install a better vapor barrier and further reduce humidity. See here....
Moldy CrawlSpace Floor....Vapor Barrier....Remove, Replace????
I will be installing the vapor barrier soon but in the short term I put a remote humidity/temp sensor in the crawlspace to monitor things. I learned this.
1. The humidity in the crawlspace is generally 5-10% higher than the basement humidity. The dehumidifier in the basement keeps things at around 45-50% inside the basement.
2. The humidity/temp in the crawlspace is very dependent on the outdoor temp humidity.
At night I notice the humidity in the crawlspace go into the 60%'s and then during the day it goes back down to around 50-55% or so. Wet weather makes it worse, dry weather makes it better.
Okay. So I need to seal the crawlspace. Obviously too much air is getting in. I want to know if my plans sound okay. What is very important to me is AVOIDING MORE MOLD!
- I plan to get some spray foam and go at all the joints in the sill and rim joist.
- Make sure the fiberglass insulation under the floor above covers the rim joist where it meets the exterior wall.
- Install rigid foam board against the concrete block wall (2-3' high). I'll use 2 for an R-value of 10.
- Install a proper vapor barrier on the floor with all seams caulked/taped.
- Install a crawlspace dehumidifier to try and keep the humidity below 50%.
What do you think? Good ideas? Recipe for disaster? Thanks!
I'm not seeing anything about venting the crawlspace. If the problem is that the dirt is getting wet from outside and then releasing vapor into the air, lack of venting could make it worse.
What happens to the water draining from your roof? Is it directed out 10' or more away from the foundation?
Is radon a concern in your area or your house?
First thing we did when we moved in was to improve the drainage. The soil actually sloped towards the house. We added soil and things drain properly now. We installed gutters as well. Radon is not a concern (as far as I know).
There is a 2'x2' opening connecting the basement with the crawlspace.
There are two foundation vents on the exterior walls of the crawlspace. I have them sealed up. When left open the humidity ranges between 60-90% because of the night time humidity.
I merged the threads so we can keep our thought process going in a single line. Hope it agrees with all.
Mold is simple, it needs food....paper, and water, to stay alive.
Get rid of the plastic and the paper and the mold will die.
Ventilating a crawl space is a waste of time and it costs money.
All it does is provide a way for warm wet air to arrive under the floor.
This is basically due to the stack effect, the heat inside your home escapes through holes, open windows and doors, it pulls cold air from the crawl space, this air costs a lot of money to warm.
Block all the holes in the crawl space, then line the bottom of the floor joists with sheets of polystyrene or similar closed cell insulation.
This will help to keep the joists warm and dry. Heat moves into the joists from the room above by radiation and conduction.
Condensation doesn't form on warm wood, no condensation....no mold! Warm home!
For BigOldXJ:
Sorry to bust in this thread but I'm trying to get info on your post about your farmers porch. Did you get my private message? Please reply when you have time. Thanks very much.
Tags: moldy, crawlspace, floor, vapor, barrier, remove, replace, vapor barrier, crawl space, away from, concrete block, plastic sheathing, access hole, barrier over
