Basement humidity level / percentage ?

[SONOCATIVO]

Stuff fiberglass in it and fill with expandable foam? Use items that wont mold or mildew due to moisture.

 

[Ashful]

I like overkill, so I'd be dropping a length of rebar in each hole and filling with concrete. If you just want insulation and moisture barrier, I'd be doing closed-cell spray foam... not Great Stuff, but one of the portable / disposable kits used by the pro's who do spray foam installs.

 

[sportbikerider78]

Yes. I am just looking for a vapor barrier. I am going to do closed cell foam sheets on the basement eventually and want to start preventing any kind of drafting.

 

[ocampo]

newbie here


Wet or damp basements are the most frequent complaint of homeowners. Traditional, decades-old basement waterproofing methods have not passed the test of time: "Over 60 per cent of basements have moisture seepage in one form or another, while 38 per cent experience mold and fungus growth due to an elevated moisture level." – The American Society of Home Inspectors. Slab-on-grade buildings suffer similar moisture problems.

 

[delp]

I like overkill, so I'd be dropping a length of rebar in each hole and filling with concrete. If you just want insulation and moisture barrier, I'd be doing closed-cell spray foam... not Great Stuff, but one of the portable / disposable kits used by the pro's who do spray foam installs.

Ashful…what's the difference between the kit closed-cell and the Great Stuff?

 

[mass_burner]

I like 45-50 %. It also keeps the space a lot cooler. On a 90d day, 80% humidity, folks think I have AC in the basement.

 

[Ashful]

Ashful…what's the difference between the kit closed-cell and the Great Stuff?

I wasn't saying I wouldn't use Great Stuff because it's not closed cell, I was saying I'd be using a portable kit over cans of Great Stuff due to the size of the job. I've only used Great Stuff a few times, but I think it actually is closed-cell foam.

 

[delp]

I wasn't saying I wouldn't use Great Stuff because it's not closed cell, I was saying I'd be using a portable kit over cans of Great Stuff due to the size of the job. I've only used Great Stuff a few times, but I think it actually is closed-cell foam.

Thanks for your thoughts Ashful! I just finished doing a "poor-person's" joist cavity insulation project at my house. Since it's easily reversible and ended up costing less than $100, I used 2" foil faced rigid insulation cut about ½" shy of the two dimensions and sealed it in place with great stuff. Hoping this winter will see less air infiltration in the basement.

Anyway, I thought I had missed something I should have known about the Great Stuff when I read your post.

 

[blades]

Delp ,no, you did ok, eps closed cell in joist cavities and on top of sill -seal edges with any of the various spray cans of foam. there are some that are water clean up( latex based) vs great stuff- work just as well. sheet foam by what I have read about 2" thick . Fiberglass batts allow too much air passage and with that vapor passage as well. the key here is to not allow an air gap at the floor sill framing doing so could allow moisture to condense behind foam. Of course total sprayed in foam is the best. small kits are available from the various box stores. these are kind of pricey from what I have seen to the point where a contractor isn't all that much more saves headaches. Years ago when I read about this ( Mother Earth news early 70's ) I went and felt around the top of my blocks, holy yikes the amount of air traveling up out of blocks felt like a hurricane in some places in that particular home. Spray foam was brand new back then then and the formaldehyde issue was just being raised, so most were doing fiberglass, since that time the dirty truth about air migration and r value shrinkage of fiberglass( as the temps dip) has seen the light. Mfgs of fiberglass knew it, public didn't still isn't widely known and is being down played by the fiberglass mfg. ( pretty standard operating procedure for mfgs now days- case in point,automotive ignition switches as a point of reference)

Granite counter tops are taking a hit now from the radon issue- being played upon by the the alternative counter top mfgs ( course they conveniently forget to mention their own issues as far as toxins are concerned.) Ceramic tile counters are taking hits as well - not the tiles but the grouting and under layment being a home for nasties - so its difficult to win no mater what.

Course with all that air traveling through the basement- Radon wasn't an issue- something else that has not been taken into consideration ya sure they take a reading right at the sump and it goes high right there and oh my ya got to spend a couple grand to mitigate it - where as in the rest of the space it possibly is way below minimums over all. Scare tactics for sales. Not all of us have super tight sealed up homes - sometimes not even all that possible short of tearing half the structure down. Isn't it amazing that so many of us survive past 30 years old vs all these terrible things.

 

[dunned8698]

Drifthopper, have I ever got the answer for you. You could fix the problem by this afternoon, I did, and that was 5 or 6 years ago. Everyone is going to love this!!

I had a bad humidity problem, and you could smell it when I opened the basement door. I used a dehumidifier for years, and played the empty the water jug game 2 times a day for years, and it drove the electric bill up the old wazoooo.

Then one day I'm driving home from work and hear an advertisement on the radio, and it was asking if I had a damp moldy basement, bla bla bla, visit our website. So I visit the site, and it shows a vertical piece of duct work, starting a few inches from the floor, and just before the ceiling it exits into a hole in the wall. So the site goes on and on about how great it is, letting you think there is some kind of magic going on, because they weren't saying how it works, but it was going for $1200.00, which you only find out by calling them. So I pull up the reins on my pony, thanked him for his time and didn't get scalped that day.

Anyway, I'm looking at it and thinking there couldn't be much more than a fan and motor in there. So I hop my pony on down to the local Home Depot, tail and all, and I figured I'd do a little experiment, found a little motor with a 9 bladed plastic fan, already mounted in a piece of 8 or 9 inch duct. Its intended use is for when you have a cold room, you draw air from the warm part of your heating system and direct it to the cooler room. The motor is the same one they used to put in the old record players, totally silent, and I bought a flexible hose. My basement window pains come out by sliding a small piece of tapered metal, which held the glass in place. I replaced it with a piece of plywood and cut a round hole for the duct. Then I attached the hose and made it so it hangs about four inches off the floor. When I tell you that within one hour the smell was totally gone I'm not kidding. My wife and I were almost beside ourselves in disbelief. There is just a pleasant neutral smell, and very comfortable, which is now my man cave. Got my hobby table, exercise equipment, room for jogging, rc cars and helicopters, and I'm the man now.

The unit they were selling had a humidity sensor to shut it off and on. Big woop. And they wanted hundreds of dollars to install it. My fan runs 24/7/365 and costs $10 per year in electric, that's right ten dollars. I just replaced the motor in 2012. It still ran but would stop for whatever reason, and go again if I pushed the fan, so I figured I got my moneys worth out of it and didn't want any problems, and was probably on it's way out anyway.

What happens is that in the summer the hot outside air gets in and contacts the cooler surface of the basement walls, hits the dew point, which is when a certain amount of hot hits a certain amount of cool, and moisture forms by condensing, which is called condensation. Never ever open the windows in the summer as it will not dry out anything.

By having the fan going all the time the air never has a chance to condense. My fan actually changes the basement air two times per hour. You just figure out cubic feet of the basement and how many cubic feet an hour the fan moves. And guess what, if I did have that horrible gas called radon, which rises from the earth in enclosed spaces, it's gone too. So I don't mind having it running all year, especially for ten dollars.

Guess what, in another article I told about closing all my hot air registers, since I heat with wood, because I was drawing air out of the duct work, and wasting wood, and never knew it until recently, after all the years of using wood, from the early seventies and how much better everything is, using less wood, and more stable temperature. But guess what, where my basement used to be in the fifties it's now in the sixties and it wouldn't be like that without the fan. Man talk about a good deal, this is it.

Now, I have to admit, there is ever the slightest amount of moisture, but the only way I know this is because if I keep clothes down there for a very long time it does pick up a tiny bit of smell. Big woop, the cave is rocking and rolling.

I think back then it cost me $86, so it's got to be a bit higher today, but can you say big woop?

You're gonna love this so spread the word. Any handyman could add this to his services.

Good luck.

_______________________
Heartofgold, I really appreciate your post, and want to try this in my basement. Do you have anything off-the-shelf, or a link to a website, that will explain how to put this low-level, low-power exhaust fan in my crawlspace (this "crawlspace" is a misnomer...it's tall enough that I need a ladder to touch the floor above).
Sign me, headed to Home Depot

 

[thewoodlands]

Does anyone have any info on what is an “acceptable” level for humidity in a regular house basement?

What I am asking on “acceptable” , is how high can the humidity be allowed to get before mold and mildew start to form?

House is a two story colonial, built in 1977, poured concrete basement, about 800 sq. ft. , not finished, glass block windows with center screens that I do not open, washer / dryer / work bench / furnace and wood furnace off to one end under family room, sump pump in far corner…standard, solid basement.

The guy that sold the house left an old dehumidifier, ( like from 1977 ). Seeing that it was old and having it look like a big energy monster, I would only run it every so often.

Well, one yr, un-packing Christmas decorations, quite a few items had mold on them, these were tossed.

So, two summers ago I got a new dehumidifier and a small digital temperature / humidity level reader : Temp on top , Humidity on the bottom.

Last summer, I was running the dehumidifier on “dry” (there are three settings, normal, dry, and Extra dry” ) Dry is the middle setting.

My typical humidity level was around 48% to 55% , basically right around 50%. BUT…..the machine was running ALL THE TIME.. So even with this new dehumidifier, it still added $15 to 20 bucks every month to the electric bill, spring , summer and early fall.

This season, 2010 – To save on the electric bill, I have the dehumidifier set on “normal” , it does not run / cycle near as much, but my humidity level is around 60 % to 67% ( 67% is the highest I’ve seen on the digital reader)

Basement temperature is about the same, 62, 64, sometimes 68, depending on how hot it is outside.


Now ….i understand that all houses are different and everyone’s situation/set up is different, but there has to be some type of baseline to say what is ok, and what is not.

Any input (or links for info) is greatly appreciated.

We like our basement between 35 to 45 percent.

This summer we've kept the basement windows closed because of the high humidity. Our basement temps have been between 68-70 this summer which has been nice.

 

[fbelec]

my dehumidifier has a variable dry to moist knob. i run mine halfway which the knob says is normal. feels like air cond here also. we've had mid 90's here everyday for over a week. the temp just today is up to 74 and will drop down a little by morning. before the dehum any metal started to rust and it smelled musty. nothing had mold on it. i go into alot of basement with my job and i find most people do the wrong thing with there dehum. they plug it in and turn it all the way to the driest setting. it sends the electric bill up for energy used and burns out the dehum in about two years and then we can talk about the heat that it makes in the basement which in turn heats up the next floor above. you might think that it's not dry enough so turn the unit lower. dehum's are made to do a certain amount if it is not doing it instead of cranking the unit to run hard get a second unit set them both to normal and it will dry out and since they both are not running hard it will be minimal on the power bill because they both are cycling like they should.

 

[Poindexter]

So how much grading? What slope, what rise and run? I am going to need a surveyor's transit to see what is possible on my lot, but a goal or starting point to work from would be nice.

The further I get into mold abatement in my 1980 build, the bigger headache it is becoming. It seems the ideal solution would be to pull the house forward on the lot about 15 feet.

I was in the crawl space this summer, I have poured concrete walls, vapor barrier over dirt for the floor, and salt stains in the concrete at opposite corners. One near the hosebib on the front and one at the down spout on the rear corner. I rerouted the downspout, five, six, seven years ago, it empties 14 feet from the foundation now...

Current plan is to rent a skid steer spring 19 and make all the slope I can around the building while still able to drain via gravity over the curb onto the street.

 

[blades]

pointdexter- some of your issues could be related to what is below the surface. Type of sub soil & ground water flows sub surface. At one of my previous homes located 1/2 down a hill and an 30 home subdivision on top of said hill created a subsurface flow that drove me nutz. ended up installing a poured concrete deflection wall sub surface, 6ft high wall about 2ft under surface back side from house piped out around & past home only way I could control it , Plus I built a surface berm for deflection of that water as well. Before the subdivision was built I had no problems. After it was built and all the homes constructed I would get a river in back yard and across the front yard- neighbor across street suffered same problems, both of us did a lot of remedial landscaping to control/ deflect water.

 

[Ashful]

Every basement water issue I've ever had, in 45 years of life and at least a dozen houses, has been resolved on the exterior:

1. Clean and functional gutters.
2. Downspouts extended away from the house, preferably running into burried pipe that surfaces more than 30 feet from house.
3. Filling any low spots around foundation, so all slope is away from foundation for at least 3 feet.
4. Installing drain pipe, where all else fails.

It's the rare house that will have a wet basement, after following these four principles.

 

[blades]

That home was dry as a bone for many years prior to the new subdivision. Problem was /is caused by all the run off up there as well as sumps pumping out. The blame really lies with the city. Couple other areas same thing occurring enough so that the owners in one subdivision are suing the city to rectify there oversight in regards to what the developer did or did not do.

 

[Ashful]

I hear you. In PA it is illegal for any property development to affect runoff to or from an adjacent property, so it would be a pretty cut-and-dry case here. No plans would be approved that consisted of grading which would affect runoff toward your property, and if somehow that managed to happen, the burden would be on the developer to remedy the situation. You might want to check your local laws, as I suspect they’re similar.

 

[Highbeam]

I hear you. In PA it is illegal for any property development to affect runoff to or from an adjacent property, so it would be a pretty cut-and-dry case here. No plans would be approved that consisted of grading which would affect runoff toward your property, and if somehow that managed to happen, the burden would be on the developer to remedy the situation. You might want to check your local laws, as I suspect they’re similar.

It’s not that simple. No, the burden is on the affected homeowner to prove that this new problem is new and that it is caused by the new project. It’s almost never the city’s fault, the project plans were stamped by an engineer.

 

[Ashful]

It’s not that simple. No, the burden is on the affected homeowner to prove that this new problem is new and that it is caused by the new project. It’s almost never the city’s fault, the project plans were stamped by an engineer.

It is actually fairly simple if you can show that the developer deviated from the plans. It is also not that difficult a case if it can be shown that the plans create a problem, and were approvoved in error.

The more difficult case is when the plans were followed, and there is no clear deficiency in the plans. Then you have to resort to historical data, such as comparing conditions that cause recent flooding to past similar or worse conditions that did not, and proving there are no new maintenance issues or mitigating factors that would contribute. I’d agree with you, if this were the case.

 

[Highbeam]

It is actually fairly simple if you can show that the developer deviated from the plans. It is also not that difficult a case if it can be shown that the plans create a problem, and were approvoved in error.

The more difficult case is when the plans were followed, and there is no clear deficiency in the plans. Then you have to resort to historical data, such as comparing conditions that cause recent flooding to past similar or worse conditions that did not, and proving there are no new maintenance issues or mitigating factors that would contribute. I’d agree with you, if this were the case.

As I read it, we are saying almost the same thing. Yes I am a professional engineer and yes I do this for a living.

 

[Seasoned Oak]

We like our basement between 35 to 45 percent.

Thats seems very dry. The mayo clinic recommends between 45 to 50 as ideal. Too low can dry out your nasal passages and encourage illness. Too low can also cause nose bleeds. Notice the flu and colds are much more common in winter. I shoot for 50 to 60 for our below grade finished basement. We suffer over winter when it stays consistently below 40%.

 

[thewoodlands]

Thats seems very dry. The mayo clinic recommends between 45 to 50 as ideal. Too low can dry out your nasal passages and encourage illness. Too low can also cause nose bleeds. Notice the flu and colds are much more common in winter. I shoot for 50 to 60 for our below grade finished basement. We suffer over winter when it stays consistently below 40%.

I think we hit 37 percent once last summer but the majority of the time we're at 47 percent with a temp between 68-72 this summer.

 

[ChuckTSI]

Have an old 1850 stone home. They built the interior walls inside the stone walls. Only the main center beam sit on the stone. And that is a problem. Stone needs to breathe. If I attempt to seal off the cellar from moisture (30x20 @ 6 feet hight).. I will end up with water in the stones that won't be able to escape and start causing problems in the winter. The mortar will crumble, etc. There are way to many entry points for air to get in.

I have been doing lots of reading. Everyone says. spray foam the stone. Done. But I don't believe it's that simple. Again, stone needs to breathe.
The basement is at 94-96% humidity in the summer. temps are never higher than 16 degrees C down there and the hot humid summer air just rushes in and condenses. The reverse happens in winter. same condensation build up as the cellar never drops below 1 degree.C

Previous owner threw up 2x4 framing and pink insulation right up against the rock. When I bought, the insulation was all sagging and the 2x4 were black mold. I removed it all. The basement improved greatly, but it's still @94-96%. Floor joists seem to be in good shape except the header where cold is rushing in from old windows that they never put in. Was just pink insulation with boards leaning outside the house.

I can't put a dehumidifier. It will never win against outside air coming in.
I can't seal it. Stone needs to breathe or risk greater problems.

I have closed off those windows and used rockwool instead of pink fiberglass.
I added interior perimeter drain to improve drainage to the sump.

I have thought of pinning that dimpled sub floor stuff to the walls. down 4 feet from rim joist. (allow air to pass behind and the stone can dry out).
Then adding pink styrofoam rigid board (down 4ft) over it.
I would then add 2 layers of 6mil plastic down on the gravel floor. Leaving 12" around the edge of the room for the air to move between the walls and the room. The walls are never really wet. If they are it's only due to condensation. not seepage through from ground outside.

The idea for me I think it to reduce the surfaces that can release moisture directly to the room. I will never be able to seal it unless I spend 100K to get the foundation redone.

 

[Ashful]

Have an old 1850 stone home. They built the interior walls inside the stone walls. Only the main center beam sit on the stone. And that is a problem. Stone needs to breathe. If I attempt to seal off the cellar from moisture (30x20 @ 6 feet hight).. I will end up with water in the stones that won't be able to escape and start causing problems in the winter. The mortar will crumble, etc. There are way to many entry points for air to get in.

I have been doing lots of reading. Everyone says. spray foam the stone. Done. But I don't believe it's that simple. Again, stone needs to breathe.
The basement is at 94-96% humidity in the summer. temps are never higher than 16 degrees C down there and the hot humid summer air just rushes in and condenses. The reverse happens in winter. same condensation build up as the cellar never drops below 1 degree.C

Previous owner threw up 2x4 framing and pink insulation right up against the rock. When I bought, the insulation was all sagging and the 2x4 were black mold. I removed it all. The basement improved greatly, but it's still @94-96%. Floor joists seem to be in good shape except the header where cold is rushing in from old windows that they never put in. Was just pink insulation with boards leaning outside the house.

I can't put a dehumidifier. It will never win against outside air coming in.
I can't seal it. Stone needs to breathe or risk greater problems.

I have closed off those windows and used rockwool instead of pink fiberglass.
I added interior perimeter drain to improve drainage to the sump.

I have thought of pinning that dimpled sub floor stuff to the walls. down 4 feet from rim joist. (allow air to pass behind and the stone can dry out).
Then adding pink styrofoam rigid board (down 4ft) over it.
I would then add 2 layers of 6mil plastic down on the gravel floor. Leaving 12" around the edge of the room for the air to move between the walls and the room. The walls are never really wet. If they are it's only due to condensation. not seepage through from ground outside.

The idea for me I think it to reduce the surfaces that can release moisture directly to the room. I will never be able to seal it unless I spend 100K to get the foundation redone.

I have a dry finished basement, parts of it dating to the 1730’s, and the newest corner of it being 1779. It’s not that difficult. I have lived in nothing but old houses (some dating back to late 1600’s) my entire life, and I’ve gotten the basement in every last one of them to hold 50% RH.

In rough order of importance:

1. Repair or replace any broken or missing gutters.
2. Run all downspouts into buried PVC piping, drained downhill, far from the house. If you can’t do this, at least extend all downspouts far from house, and downhill.
3. Fix any grading around house that sends water toward foundation.
4. At a minimum, pour a slab floor. Better is to dig, install perf pipe, gravel, then pour. My current house has the latter solution, but my two prior houses just had slab poured on dirt floor.
5. Install a dehumidifier. If it hasn’t stopped running after a week, install a second dehumidifier. I have two in my current basement, but it’s over 2000 sq.ft. and broken into several rooms.
6. Seal around all basement doors and windows. Seal sill plate or joist penetrations.
7. Insulate and/or seal basement ceiling, if living space above is not air conditioned in summer.

You are correct, you do not want to directly seal the stone, but stone does not release so much moisture into the basement that a dehumidifier won’t keep up with it. Air infiltration and a damp dirt floor are the primary enemies, here. Stone walls do pretty well, with regard to air infiltration, if you seal doors, window, and sill plate / joist penetrations. I have done this in several cases, and have always achieved RH = 50%, where previous owners had assumed the basement could just never be dry.

Note that items 1 - 3 are all about keeping water away from the foundation. This is the number one problem, in my experience.

 

[ChuckTSI]

I have a dry finished basement, parts of it dating to the 1730’s, and the newest corner of it being 1779. It’s not that difficult. I have lived in nothing but old houses (some dating back to late 1600’s) my entire life, and I’ve gotten the basement in every last one of them to hold 50% RH.

In rough order of importance:

1. Repair or replace any broken or missing gutters.
2. Run all downspouts into buried PVC piping, drained downhill, far from the house. If you can’t do this, at least extend all downspouts far from house, and downhill.
3. Fix any grading around house that sends water toward foundation.
4. At a minimum, pour a slab floor. Better is to dig, install perf pipe, gravel, then pour. My current house has the latter solution, but my two prior houses just had slab poured on dirt floor.
5. Install a dehumidifier. If it hasn’t stopped running after a week, install a second dehumidifier. I have two in my current basement, but it’s over 2000 sq.ft. and broken into several rooms.
6. Seal around all basement doors and windows. Seal sill plate or joist penetrations.
7. Insulate and/or seal basement ceiling, if living space above is not air conditioned in summer.

You are correct, you do not want to directly seal the stone, but stone does not release so much moisture into the basement that a dehumidifier won’t keep up with it. Air infiltration and a damp dirt floor are the primary enemies, here. Stone walls do pretty well, with regard to air infiltration, if you seal doors, window, and sill plate / joist penetrations. I have done this in several cases, and have always achieved RH = 50%, where previous owners had assumed the basement could just never be dry.

Note that items 1 - 3 are all about keeping water away from the foundation. This is the number one problem, in my experience.

Thank you thank you thank you Glad to hear there is hope. I will follow your plan to a T (other than slab floor. That will never happen until the house is paid. Or if I get ambitious with a cement mixer and 800 bags of concrete. >.<)

1. Gutters and downspouts are almost complete. I was afraid of the PVC pipes freezing underground. How far down you put them?
2 & 3. Little bit of mortar work at ground level to do and then grading is next.
4 Already did the perimeter drain inside. It's gonna have to be 6mil plastic for now.
5. Bought Dehumidifer early 2017. Just waiting till I finish the work above to install.
6. This is an old root cellar. no access from inside the house. You open a trap door at ground level, then walk down very steep steps to a door into the cellar under the main living area. Almost done sealing the old window areas.
7. I air condition in the summer. But the temperature in cellar never exceeds 16 degrees and I have AC set to 21. I still want to install Reflectix between the joists just for a little added comfort in the winter from the FREEZING floor. If I install Rockwool batts, afraid the mice will get into it.