Condensation at a basement window (C) Daniel FriedmanBuilding Moisture Problem FAQs

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Questions & answers on how to cure high indoor humidity, moisture or "sweating" surfaces & pipes:

Frequently asked questions on the diagnosis & cure of indoor moisture, high humidity, wet areas, or dampness.

This high indoor humidity article series explains the causes and cures of high indoor moisture or indoor condensation problems. High indoor moisture levels can lead to costly mold contamination problems as well as insect attack and rot on buildings.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Moisture-Caused Building Problem FAQs

Condensation caused mold on window (C) Daniel FriedmanRecently-posted questions & answers about moisture problems in buildings

Excessive indoor moisture problems on buildings are often difficult to diagnose and cure, largely because although the physics of moisture vapor transmission, air flow, and dew points is well known (but complicated), the movement of moisture in buildings is often complicated and not obvious unless invasive measures (cutting holes to look) are used.

On 2017-02-18 by (mod) - condo unit is having strange moisture issues.

Karen, if you can't find the leak yourself (look at the condensate handling for your air conditioning, not just water lines and drains) you probably need an experienced home inspector. Check out the EXPERTS DIRECTORIES link at the top links of any inspectapedia page

On 2017-02-18 01:16:28.388994 by karen

I live in California we've been having a drought for many years but my condo unit is having strange moisture issues. It was built in 1968 stucco outside walls, attached to 3 more units. My patio dirt is always wet even if it's 110 outside. I don't water and checked all sprinkler lines for leaks in my patio.

Most days my carpet is wet started around the edges but now it's all ruined. Vaulted ceiling beams sometimes drip in living room. It's a one story unit, rarely rains but have had the roof leak a few times in kitchen. No one can find the leak. Maybe under slab?

Condos aren't easy to test for leaks since we share a water line and meter. The entire complex the grass is soggy and the units are drawing up he ground moisture so is our wall efflorescence on most units, and layers of my stucco is gone but that happened before the sprinklers were turned off I can't get the water bills to see if there was a spike In cost or use and having one meter for 28 units doesn't help.

My house stinks, my dog is sick and often my feet feel like something bit me. Maybe allergic reaction to a mold spore. 2 humans, sharing one bathroom, don't cook that much to make moisture inside and not sure what water vapors means but sounds like may be a factor. Thanks

On 2015-11-10 16:23:23.200949 by (mod)


What am I stop-gapping: the peeling paint? Condensation, moisture, leaks?

On 2015-11-10 15:49:28.742139 by Roger

The Goshen IN Historical Society has a old 2 story building with 12" solid brick walls. The upstairs is not presently used and is not heated. The paint is flaking off the walls and is the worst on the end walls and the north wall which has no building next to it. Please advise of a stop gap measure as at the present time we do not want to heat this area.

On 2015-11-09 23:57:12.642028 by (mod)

Then a dehumidifier is what you want, if it can handle the area you're concerned with.

I'd also double check that there are no hidden leaks into the building that might be raising the indoor humidity.

On 2015-11-09 23:49:15.392796 by Denise in Georgia

Thanks for the quick response guess I should have told you that I have not had the ac unit on the inside actually feels warmer than the outside without running heat got a dehumidifier it is helping some

On 2015-11-09 21:10:49.263251 by (mod)


If you are not running A/C (to dehumidify the indoor air) and the indoor temperature is lower than outside, warm moist air leaking into the home will send moisture condensing out on the cooler floor surface. Stopgaps include raising the indoor temperature, increasing indoor air movement with fans, turning on the A/C or running a dehumidifier.

On 2015-11-09 20:57:35.190279 by (mod)

Seems crazy doesn't it: we put in air conditioning to cool the air then add a heater to warm the air to try to "cut humidity"

Actually heating the air increases is ability to carry moisture - that'd reduce indoor condensation but not lower the humidity directly.

I think we both suspect that the systems installed were over-sized. If that happens we explain in the articles in this series that the air cools down too fast - before we've also removed enough humidity. Removing humidity takes more time and more air flowing across the coil.

So, see if your system will allow for a reduced fan speed - slow the fans down to give more time to dehumidify. THat might save the system, and even if you had to install a different fan to permit slower operation it might be worth it.

An HVAC engineer ought to be able to make RH measurements, air flow measurements, and if necessary, do the calculations to see what would be the optimal HVAC size for your home.

Keep me posted.

On 2015-11-09 20:52:20.967112 by Rich

We completed construction recently of a new building in a southern coastal region. Well insulated with spray foam, and from some thermal testing (supposedly) we're not leaking in the space. The split-system HVAC (18 seer Trane) units are, in my opinion, oversized: 3 ton system and 5 ton system (total 8 tons) for a 2200 sq ft space.

We have had constant humidity issues... it took a good month of living there and recognizing clamy, damp, musty environment for me to get a humidity reader to be sure. It would show 75-80% humidity (and usually more than what it was outside).

The AC guys added a dehumidfying thermostat to the units to additionally warm the air to help take humidity out... and while it has improved it down to about 60%, it's killing my electric bill now, and obviously is just a band-aid to the real problem.

My main question is: I need to find an expert that can analyze the humidity problems, energy efficiency, the spec'd systems, the MEP plans and help determine what is causing the issue definitively so I can have the guilty party fix it at their cost.

What type of consultant/engineer should I be looking for that might specialize, and has likely seen this situation before? I'm going to seek out the best type of consultant in the greater proximity of my home.

On 2015-11-09 11:46:38.904032 by Denise

Just purchased home in Georgia has crawlspace floors are hardwood when it's rainy or humid outside the floors get wet and indoors is humid any ideas?

On 2015-11-02 20:45:14.740391 by (mod)

I would not add insulation before fixing the moisture or leak problems.

On 2015-10-06 10:00:27.355610 by

I had the water pipes burst in my house awhile ago I still need insulation in attic . I have noticed moisture build up on my first floor surface sometimes it goes away when I turn Ac on first I thought it was a pipe under the house but no spike in water bill, is.built on concrete slab

On 2015-09-29 10:36:45.322655 by jayaprakash

we have manufacture the asbestos building boards in Bangladesh. At present we have got one problem regarding in moisture.
Our sheet thickeness is 4mm . Hereafter the sheet lying on the sunlight for 1 hrs and after that we apply the water on the sheet appears. but sheet are shrink (center its bend). We have not known the how its bend. Please adviced me.

On 2015-08-11 18:24:36.889441 by (mod)

Take a look at some of the insulating foam options at

If the wall area is large you'd want to hire an insulating company but frankly they won't want to even come to bid on a small insulation retrofit job - or the price will reflect that reluctance.

So I'd look at a DIY foam project. There are its and rental kits. But keep in mind that spraying foam is messy and sticky so you'll want to read the instructions and think about how and where you'll be inserting the foam.

Also you want to have some confidence that through the opening(s) you make you can fill the entire cavity.

On 2015-08-11 18:06:15.709455 by Chris

Thanks for your help.

On 2015-08-11 17:56:17.868302 by (mod)


Your note is a bit dense and was rough going but I think you want to add insulation in a wall cavity. Once all of your construction has been completed probably the best bet rather than having to tear something apart is to choose where outside or inside you can make a hole to pump foam insulation into the wall cavity with least disruption.

On 2015-08-11 15:19:18.018158 by Chris

I recently purchased a home in Louisiana that came with a one piece fiberglass shower. A couple of months ago I decided to replace the fiberglass shower with a new tile shower. I used a Schluter shower kit from Home Depot to build my own tile shower.

After completing the shower I realized that I made may have made a catastrophic insulation error and I am trying to determine the best way to fix it. I am hoping that you can help provide me with some guidance on this issue. 1 of my 3 shower walls is located up against an exterior wall of my house. This exterior shower wall is approximately 3 foot wide and 9 feet tall. When I took down my old fiberglass shower there was no insulation anywhere behind the fiberglass shower itself.

The only insulation that was in place was a couple of strips of fiberglass batt insulation, which were located behind a section of drywall that was located just about the fiberglass shower unit on the outside wall. When I started building my tile shower I mistakenly assumed that I didn't need to put insulation anywhere behind my new tile shower since there was no insulation behind the original fiberglass shower.

I completed the shower approximately 2-3 weeks ago and have taken a handful of showers at this point. I noticed fairly quickly that the uninsulated outside wall of the shower gets slightly warm when the sun shines on that section of the house in the afternoon.

My house has a layer of brick veneer and OSB sheathing that has been wrapped with house wrap (Tyvek). After doing some reading I stumbled across several articles about inward solar vapor drive and the problems that polyethylene membranes can cause with this phenomenon. This makes me worry that I have set myself up for a potential mold disaster. As a result of this I have stopped using the shower until I can figure out the best solution.

Looking back, I cannot understand what I was thinking to not put insulation along this exterior wall. The reason I am writing is to see if there is anyway to salvage the shower that I currently have in place or if it would be best for me to remove what I have done and start over from scratch after I have properly insulated the outside wall. Any help you can provide with this matter would be greatly appreciated.

Here is a little more background on how the shower is constructed: As I mentioned earlier, I used the Schluter shower system to construct my new tile shower. The kit comes with a waterproof Kerdi membrane that is supposed to keep the vapor from the shower from entering the walls. When I was building the new shower I used concrete backer board over the studs. I then placed the Schluter membrane on top of the concrete backer board.

After the membrane was in place I tiled directly on top of the membrane according to the manufacturers instructions. I guess the bottom line is that I need to somehow get some insulation installed on the one wall of my shower that is located on the exterior wall of the home.

However, I am not sure if this is possible at this point. Even if it is possible I am worried that I will not be able to achieve proper insulation coverage and therefore, may still have a potential mold problem on my hands after insulation gets added. Any help you can provide would be greatly appreciated. Thank you so much for your time.

On 2015-07-16 17:15:34.548987 by Daniel (mod)

You are describing a significant amount of moisture and a risk of some costly trouble. I suspect a combination of high indoor moisture and inadequate wall insulation so that the wall surface or wall cavity are reaching the dew point.

On 2015-07-13 23:49:02.760660 by Beth

(Condo question). Walls sweat only in winter months, October thru February (florida) only on walls that are parallel to the outside walls. No pipes or any water source behind the walls. I am on second of third story building. No attic, no roof leakage.

Mold forms after the water has saturated walls. Sometimes I see water dripping from ceiling to floor. And pools in the corner of bedroom and bathrooms not any other room in unit. Just the outer walls of the unit. Is this structural, a/c problems? Summer months no sign of water or mold.

On 2015-04-13 00:35:18.850300 by (mod)


I would want some objective data such as measurements of the relative humidity of the indoor air and a visual inspection for condensation on building surfaces if investigating a complaint that indoor RH is too high.

If there is a high indoor moisture problem and it's a new complaint, I'd be looking for a leak into the building ceilings, walls, basement, or crawl space.

On 2015-04-12 17:30:02.042010 by Craig Garfield

PS forgot to mention that exterior has been stuccoed, no weep screed, of course--I kind of like this for causing mischief

On 2015-04-12 17:28:20.093810 by Craig Garfield

older,1951 masonry home FEELS LIKE IT HAAS obvious excess moisture IN AIR and moisture behind the dry wall (hole cut to verify) flat topped roof has been sealed, eaves covered, 2nd drywall sheet added in some rooms (front bedroom has this on exterior, load bearing wall--?

WHAT IN THIS ARRANGEMENT IS MOST LIKELY TO BE CAUSING MOISTURE BUILD UP BEHIND INTERIOR DRYWALL? ANY IDEAS AT ALL? have used process of elimination, including camera in all water pipes, including under the slab

any help appreciated and thanks

Pillar to Post Home Inspectors-Tucson Az

Question: increase in house humidity since exterior was 'bricked'

(Oct 23, 2012) Jim said:
My friend had the exterior of his house bricked 2 years ago. Since then he has noticed an increase of humidity in the house. An example is that the floor vents would be wet with condensation when the AC was run. He has purchased a humidifier which generates 21 pints of water in 12 hours.

The vents have stopped sweating. What would some of the causes of this humidity problem?


Jim, the general approach to tracking down the high moisture problems in the house you describe would include

- look for indoor moisture sources: a wet basement or crawl area
- look at the changes in house design: perhaps an impermeable barrier was placed on the exterior walls when the brick veneer was added, and the veneer wall may also not be properly vented and drained
- look at other house moisture control methods: for example the condition of the roof and attic ventilation

But I prefer to start with my first point as we want to know that we're not dealing with an abnormal indoor moisture source.

Question: air in our house always feels wet, stuffy, heavy

(June 26, 2014) Michelle said:
the air in our house always feels heavy (wet) and stuffy. our house was once a 1 story ranch. a previous owner had a dormer room add onto the 2nd floor and finished off the attic and above the garage so that it is now a 2 story ranch. they removed the ridgecap and stuffed the soffit vents and turned the entire space into "conditioned space". When we moved in a year ago, we noticed right away that we had high humidity - everywhere.

We had the AC replaced on first floor and serviced the 2nd floor AC unit. The humidity level was still too high. We had the crawl space encapsulated and the air is now "conditioned space" with a small vent from the duct open. the humidity level was still too high (70-80% under house) and indoor varied from 65 to 75% RH.

We had a permanent dehumidifier installed in the crawlspace with external discharge. the 2nd floor seemed to have a "heavier" air feeling so we put in a dehumidifier which is emptied daily. the humidity level went from 78% under house to 60% within 24 hours of installing the dehumidifier but it runs constantly.

There is NO visible water in the crawlspace and the floor under the plastic barrier feels solid (no pockets of slushy mud). the house is brick veneer. I purchased a professional humidity gauge and placed some cheap thermometer/humidity gauges all over the house to monitor the levels of moisture in crawlspace, 1st floor and 2nd floor.

the outdoor humidity is currently 85% (we live in Virginia). The humidity (with AC set to range between 71 to 75 degrees) continues to be a problem. Both ACs are draining fine.

Is it possible the moisture could be migrating from outside to inside through the brick?

This is the first time we've lived in a brick house and it seems to me that brick would absorb moisture and that it would migrate into the house? What more can I do to determine where the moisture is coming from? It is not infiltrating from ground water under house. The roof was inspected and does not appear to be leaking anywhere. thank you.



It's indeed smart to look at both sides of a humidity problem, the water source and the water removal.

Yes moisture can migrate into a building through masonry including concrete floors or masonry walls. I'd look at the roof drainage system outside to start.

But let's look at the AC system. If it is oversized the air conditioning system will cool down the home without dehumidifying It.

Question: Tuff-Wrap moisture trouble and swelling OSB sheathing

(July 4, 2014) kevin said:
I have a problem moisture under my Tuff-Wrap energy seal. The OSB sheathing is swelling and black staining. It seem to me air infiltration barrier is holding the moisture in , causing the problem. I'm looking for answers what I should to fix it.

I found the problem when I went to replace windows on the back of my house. Now I do have a basement bathroom/shower under that area in the house. Is all the moisture coming from there?



The air barrier is designed to allow *moisture* to pass out but not to pass actual water droplets.

So if moisture is entering and condensing inside the wall and then contacting the barrier in that form indeed it can be trapped.

Presuming you are in a heating climate where the house wrap is on the exterior side of your wall (over wall sheathing but under finish siding) then you want to take at least these troubleshooting approaches:

Outside: look for possible leaks into the wall cavity such as around wall penetrations where flashing may be incomplete or incorrect, or leaks due to winter ice damming

Inside: look for sources of high indoor moisture: basement leaks, plumbing leaks etc.

Question: walls are sweating

(Sept 14, 2014) Katlyn said:
I think we had the central air set to low all summer now all the walls are sweating. How do we dry the walls without leaving the walls stained from the water running down walls.



If water is already on your walls from condensation you will want to run one or more dehumidifiers and fans to obtain the fastest dehumidification, along with wiping wall surfaces with a dry cloth to avoid rivulets of water that may leave stains.

Question: bathroom condensation troubles

19 January 2015 Dewayne said:
I have a moisture problem in my house in the master bathroom it has condensation around the edge of the floor every day can't figure out where it comes from we have tried everything we run the exhaust fan when showering checked the vapor barrier we have checked everything


Dewayne, try measuring the actual relative humidity in the bath where you are seeing condensation - if the RH is high and there are cool surfaces moisture will condense on them.

If RH stays high in just that room (compared to elsewhere in the house) I'd look for

- hidden moisture sources, leaks

- absence of adequate heating

Moisture Diagnosis & Cure Articles


Continue reading at MOISTURE PROBLEMS: CAUSE & CURE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.







Suggested citation for this web page

MOISTURE PROBLEM FAQs at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman