Large clay crawlspace in 90 yr. old house. Moisture/mold problem. Need advice.

[ncjay]

Hello everyone. I've been somewhat of a lurker here for a year or two and this is my first post. Hoping to get some advice about water/moisture in my 90 yr. old bare earth basement/crawlspace. After 2-3 waterproofing guys have flaked on my over the last year I ended up having a decent experience with a local Terminix guy but want to be sure I'm using my $ wisely.

I had significant water in the basement this winter after lots of heavy rain. I have since had a new sewer line from outside my basement to the road put in. I have not had any significant standing water since (which seems gross to think that I may have been digging a couple emergency drain troughs and pumping out sewage before that.) I still have significant moisture trapped in the clay and beginning to seep into the wood (mold and I even spotted a couple mushrooms in the dirt floor.) I'm working on the gutters and drainage outside but more needs to happen in the basement.

1) Just like anything I'm trying to balance doing a sump with spider drains on my own against how much work that will take me away from. I'm self employed and busy with work and have exactly zero tools or experience. But the project does not seem that hard and the area for drains/sump is fairly small.
2) Terminix quoted me just over $3k to put in spider drains to the center of the basement, install a sump, poly (?), and pour/level stone to create a semi usable storage area. They also suggested some temp controlled vents (+$700 for 12.)
3) For another $5500 they would further suggest encapsulating the entire basement in plastic and a dehumidifier in which case vents aren't necessary. I'm not sure how that would work if they already put in stone?
4) I question the effectiveness of a sump if the moisture seems to be trapped in the clay but I don't know any better.
5) I can't imagine vents (even temp controlled ones) would be much use in summer/winter and the suggestion was made to add a dehumidifier to the ~$3k job. Vents don't seem like an energy efficient combination with a dehumidifier. Wouldn't it just have constant new air to work on? Perhaps the dehumidifier wouldn't necessarily run if the vents opened themselves?
6) I know I could do the first ~3k part of the job myself but I feel like money might be worth my sanity (the basement is in rough shape and a level stone floor alone sounds amazing) and would help to save the wood from getting worse. I haven't even had time to paint so I'm not sure how I would find the time. I'm guessing I could do this for around $1k or less but I have no idea about the stone.
7) Assuming I go ahead with a dehumidifier is a consumer version with a pump to the sump sufficient for a ~900 sq ft. area or is a more commercial version (~$1k) more energy efficient for a nearly open/drafty (vented?) basement.

I have more questions but hopefully you'll have some ideas for me and I don't want this to get too long. Thanks!

[Fishindude]

If you have the water infiltration stopped, get the space ventilated and a fan or two down there moving some air around to dry things out.
Once dry, the mold should go away.

New homes built on crawl spaces typically have a plastic vapor barrier laid over the bare earth, then covered in pea gravel, and several foundation wall vents around the perimeter to allow a little air movement.   Vents are opened in summer and closed up in winter.

[ncjay]

Thanks Fishindude. Based on the fact that the house is 90 years old I don't know that the water infiltration will ever completely stop since the house doesn't even have footers on the foundation and water seeps in the clay soil every time it rains. It's not running water anymore thankfully but still moist soil. Your advice makes sense but I'm still not sure what to do in winter during the rain. Won't that moisture be stuck in there without the vents open? Perhaps that's the time to run the dehumidifier? Thanks again.

[john6221]

I would recommend going to greenbuildingadvisor.com and posting this question as well.

[shuellmi]

Where are you located?  Solution depends on climate, though slipping the grade away from your house is priority one. 

I think they are telling about 2 completely separate solutions, either add temp controlled vents or seal and dehumidify.

Without knowing your location, I suggest sloping the grades, cutting some vents, and a laying a sheet of poly.  Vents can be opened in the summer and filled with rigid foam in the winter

Sent from my XT1096 using Tapatalk

[paddedhat]

As mentioned, your location would be helpful, but the info. About heavy winter rains, and clay probably puts you in the southeast. The ultimate solution is to get as close as possible  to having a sealed conditioned space. This means that you have mitigated outside inputs, water, humidity, and extreme temperatures,  and you are maintaining the temp. And moisture in the space, regardless of weather. First, the space will only be under control if it's sealed, as in no vents. Vents are great, when the weather is perfect. Low humidity, warm temps, and a bit of wind. As you can guess, this happens almost never. So, the first step to Eliinating  outside inputs is to eliminate vents. Second is to view the water in the floor as something that needs to be both mitigated and isolated from the space. Install the drainage and sump pump. Cover everything with crushed stone, then a layer of thick plastic. Tape all seams in the sheets. Ideally this would then be covered with a concrete slab. This can be a thin 2" slab for a lightly used crawl space. Now the outside inputs are under control and you can dry the space. Run a dehumidifier, set to the lowest moisture setting. Usually 35-45% on the knob. It will run continuously. Drain the discharge to the sump pit. The unit will probably run continuously for months. Until it dries the wooden floor structure. Use a digital indoor/outdoor temperature and humidity weather station.  Place the outside sensor in the crawl space. When you reduce the moisture to less than 50% in the space, you have succeeded. You will start to hear the dehumidifier cycling on and off, and you can now experiment with running it on a timer and cutting the operating cycle to 12 or even 8 hours a day. In a colder climate the final step would be to eliminate any insulation in the floor joists and have the walls coated with sprayed foam insulation from the floor slab to the rim joists. I guarantee that this whole process will result in a crawl that's as dry as a ghost fart and free of issues. I spent ten years doing this on new custom homes I built. I worked in an area famous for wet, moldy crawl spaces and had exactly zero issues with any I built. Good luck

[NESailor]

As mentioned, your location would be helpful, but the info. About heavy winter rains, and clay probably puts you in the southeast. The ultimate solution is to get as close as possible  to having a sealed conditioned space. This means that you have mitigated outside inputs, water, humidity, and extreme temperatures,  and you are maintaining the temp. And moisture in the space, regardless of weather. First, the space will only be under control if it's sealed, as in no vents. Vents are great, when the weather is perfect. Low humidity, warm temps, and a bit of wind. As you can guess, this happens almost never. So, the first step to Eliinating  outside inputs is to eliminate vents. Second is to view the water in the floor as something that needs to be both mitigated and isolated from the space. Install the drainage and sump pump. Cover everything with crushed stone, then a layer of thick plastic. Tape all seams in the sheets. Ideally this would then be covered with a concrete slab. This can be a thin 2" slab for a lightly used crawl space. Now the outside inputs are under control and you can dry the space. Run a dehumidifier, set to the lowest moisture setting. Usually 35-45% on the knob. It will run continuously. Drain the discharge to the sump pit. The unit will probably run continuously for months. Until it dries the wooden floor structure. Use a digital indoor/outdoor temperature and humidity weather station.  Place the outside sensor in the crawl space. When you reduce the moisture to less than 50% in the space, you have succeeded. You will start to hear the dehumidifier cycling on and off, and you can now experiment with running it on a timer and cutting the operating cycle to 12 or even 8 hours a day. In a colder climate the final step would be to eliminate any insulation in the floor joists and have the walls coated with sprayed foam insulation from the floor slab to the rim joists. I guarantee that this whole process will result in a crawl that's as dry as a ghost fart and free of issues. I spent ten years doing this on new custom homes I built. I worked in an area famous for wet, moldy crawl spaces and had exactly zero issues with any I built. Good luck

This sounds like solid advice to my untrained and inexperienced ears.   The reason I say so is that a lot of moisture solutions may actually run a bit counter to conventional wisdom.  Example - people will open their Bilco storm shelter doors and run a bunch of air into the crawspace/basement to "air it out" in the summer when it's hot.  Well, what actually sometimes happens is that you force a bunch of new moisture into a space that's significantly cooler than the outside air, which in turn condenses into water in your crawlspace - exactly the opposite effect than desired.

I have a moist crawlspace and have been trying to seal it off and run a dehumidifier in there 24/7 at the moment.  There is a HUGE difference in air quality even after just a few days.  I shut it off periodically when it gets dry, which it fortunately does in our neck of the woods part of the year.

[paddedhat]

This sounds like solid advice to my untrained and inexperienced ears.   The reason I say so is that a lot of moisture solutions may actually run a bit counter to conventional wisdom.  Example - people will open their Bilco storm shelter doors and run a bunch of air into the crawspace/basement to "air it out" in the summer when it's hot.  Well, what actually sometimes happens is that you force a bunch of new moisture into a space that's significantly cooler than the outside air, which in turn condenses into water in your crawlspace - exactly the opposite effect than desired.

I have a moist crawlspace and have been trying to seal it off and run a dehumidifier in there 24/7 at the moment.  There is a HUGE difference in air quality even after just a few days.  I shut it off periodically when it gets dry, which it fortunately does in our neck of the woods part of the year.

Yea, the whole, "you need more ventilation" school of thought has been a never ending failure in this area. The other day I was heading out the door, mid-afternoon, and heard the local weather guy report that the dew point was 66*. That pretty much guarantees that all the "fully vented" crawl spaces in my neighborhood had sweat dripping off the floor joists, which wouldn't be surprising, since they have sweat   on the floor and the walls for months, every summer. 

You should really think about heading to Lowes or HD for a $15 digital weather station. Nothing like knowing the exact temp. and humidity of the crawl space, by glancing at a gauge sitting on the kitchen counter. I have educated my customers to pay attention to the gauge. One called recently to report that his read 77% humidity. He opened his rarely used vacation home to find not only the high reading, but slight mold on some ceilings and behind headboards. He was confused, as the dehumidifier appeared to be humming along. I advised him that my guess was that the unit was shot and just making noise, and he could confirm this by pulling the hose out of the drain and letting it run on the floor. As I thought, there was no drainage. I next recommended that he have Amazon ship him a new one, and within a few days of running the replacement unit, he was watching his moisture level drop 5% a day. I have even caught a minor water pipe leak in my sealed crawl space, by watching the gauge. 

Currently at my place it's:      72*F and 97% humidity outside.
                                              73*F and 60% humidity inside the living space.
                                              66*F and 39% humidity in the sealed conditioned crawl space.

[zolotiyeruki]

There's a part of me that wonders 1) if the soil was saturated for decades with water from the sewer line, and if therefore 2) the water issues will diminish gradually over months/years now that the sewer line has been replaced.

How long ago was the sewer line replaced?

[NESailor]

This sounds like solid advice to my untrained and inexperienced ears.   The reason I say so is that a lot of moisture solutions may actually run a bit counter to conventional wisdom.  Example - people will open their Bilco storm shelter doors and run a bunch of air into the crawspace/basement to "air it out" in the summer when it's hot.  Well, what actually sometimes happens is that you force a bunch of new moisture into a space that's significantly cooler than the outside air, which in turn condenses into water in your crawlspace - exactly the opposite effect than desired.

I have a moist crawlspace and have been trying to seal it off and run a dehumidifier in there 24/7 at the moment.  There is a HUGE difference in air quality even after just a few days.  I shut it off periodically when it gets dry, which it fortunately does in our neck of the woods part of the year.

Yea, the whole, "you need more ventilation" school of thought has been a never ending failure in this area. The other day I was heading out the door, mid-afternoon, and heard the local weather guy report that the dew point was 66*. That pretty much guarantees that all the "fully vented" crawl spaces in my neighborhood had sweat dripping off the floor joists, which wouldn't be surprising, since they have sweat   on the floor and the walls for months, every summer. 

You should really think about heading to Lowes or HD for a $15 digital weather station. Nothing like knowing the exact temp. and humidity of the crawl space, by glancing at a gauge sitting on the kitchen counter. I have educated my customers to pay attention to the gauge. One called recently to report that his read 77% humidity. He opened his rarely used vacation home to find not only the high reading, but slight mold on some ceilings and behind headboards. He was confused, as the dehumidifier appeared to be humming along. I advised him that my guess was that the unit was shot and just making noise, and he could confirm this by pulling the hose out of the drain and letting it run on the floor. As I thought, there was no drainage. I next recommended that he have Amazon ship him a new one, and within a few days of running the replacement unit, he was watching his moisture level drop 5% a day. I have even caught a minor water pipe leak in my sealed crawl space, by watching the gauge. 

Currently at my place it's:      72*F and 97% humidity outside.
                                              73*F and 60% humidity inside the living space.
                                              66*F and 39% humidity in the sealed conditioned crawl space.

What unit do you use to get humidity readings from multiple sources?  I know I could do the research but it seems you really know what you're talking about so I'm hoping to take a shortcut here ;)

[paddedhat]

This sounds like solid advice to my untrained and inexperienced ears.   The reason I say so is that a lot of moisture solutions may actually run a bit counter to conventional wisdom.  Example - people will open their Bilco storm shelter doors and run a bunch of air into the crawspace/basement to "air it out" in the summer when it's hot.  Well, what actually sometimes happens is that you force a bunch of new moisture into a space that's significantly cooler than the outside air, which in turn condenses into water in your crawlspace - exactly the opposite effect than desired.

I have a moist crawlspace and have been trying to seal it off and run a dehumidifier in there 24/7 at the moment.  There is a HUGE difference in air quality even after just a few days.  I shut it off periodically when it gets dry, which it fortunately does in our neck of the woods part of the year.

Yea, the whole, "you need more ventilation" school of thought has been a never ending failure in this area. The other day I was heading out the door, mid-afternoon, and heard the local weather guy report that the dew point was 66*. That pretty much guarantees that all the "fully vented" crawl spaces in my neighborhood had sweat dripping off the floor joists, which wouldn't be surprising, since they have sweat   on the floor and the walls for months, every summer. 

You should really think about heading to Lowes or HD for a $15 digital weather station. Nothing like knowing the exact temp. and humidity of the crawl space, by glancing at a gauge sitting on the kitchen counter. I have educated my customers to pay attention to the gauge. One called recently to report that his read 77% humidity. He opened his rarely used vacation home to find not only the high reading, but slight mold on some ceilings and behind headboards. He was confused, as the dehumidifier appeared to be humming along. I advised him that my guess was that the unit was shot and just making noise, and he could confirm this by pulling the hose out of the drain and letting it run on the floor. As I thought, there was no drainage. I next recommended that he have Amazon ship him a new one, and within a few days of running the replacement unit, he was watching his moisture level drop 5% a day. I have even caught a minor water pipe leak in my sealed crawl space, by watching the gauge. 

Currently at my place it's:      72*F and 97% humidity outside.
                                              73*F and 60% humidity inside the living space.
                                              66*F and 39% humidity in the sealed conditioned crawl space.

What unit do you use to get humidity readings from multiple sources?  I know I could do the research but it seems you really know what you're talking about so I'm hoping to take a shortcut here ;)

Interior of the home and crawl space data are from the indoor/outdoor weather station referred to above. The remote sensor is located in the crawl space, and is read as "outdoors", on the digital display located in my kitchen.  Outside temp. and humidity are real time readings posted online from a nearby government weather station.