GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Country/Cabin-type house in NJ has a sunroom & dining room built directly on a stone patio on grade.

user-1030353 | Posted in General Questions on

Hi… bought a house last year, knowing about the owner-built additions and general substandard conditions, however, last summer was DRY. THIS summer was WET. The additions on grade bring have no foundations, perimeter drainage or underslab drainage. Those ends of the house are basically 80% humidity, and the beautiful grooved wood paneling we bought the house for is starting to mildew/rot/turn color. We think the wet summer has caused a high water table (we also have basement dampness problems)… What is my biggest problem? How do I start? I can do some of the work myself.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    It's hard to correct foundation problems. If you have two rooms built on "a stone patio on grade," there are several questions that come to mind:

    1. Do these "patios" suffer from frost heaving during the winter?

    2. Is the exterior grade below the indoor finish floor level?

    3. Does the grade slope away from the house at the exterior perimeter of these rooms?

    4. If the exterior soil is saturated, is there any way to install French drains that conduct soil moisture down hill to daylight?

    5. If you have interior woodwork that is damp and showing mold, have you installed a dehumidifier?

  2. user-1030353 | | #2

    1. The patios have not "heaved" in the past. There are cracks showing, but they have not appreciably separated or changed level (so far as we can tell.) That being said - they may very well heave this year, and really mess up the roof structure where the old house and the addition connect.

    2. No, it's not, and we are getting estimates from a few sitework contractors to have a retaining wall/drainage structure built approximately 6 - 8 feet beyond the exterior wall that will allow us to drop the grade next to the house to an appropriate level (and hopefully, we can install a continuous subgrade drainage trench at the base of the wall which can span the entire yard, and send water to the perimeter of the property.)

    3. No - see above.

    4. I think instead of french drains, we might excavate down, underpin the "patio" and put in foundation/perimeter drains.

    5. I have a 70 pint/day dehumidifier being delivered (hopefully tomorrow).

    One of my major concerns is hidden mold growing in the HVAC system. Since our ductwork is under the first floor (at the basement ceiling), and our basement has been very WET, I am getting the ductwork cleaned this week (where they vacuum it and scrub it throughout all the ducts?). I would like to entirely MOVE the system up to the attic eventually. Where else in the house do I have to go looking for mold/mildew/humidity issues?

  3. BobHr | | #3

    Did they scope the duct work for mold? I like high pressure air whips and a negative air machine for cleaning.

    If the AC was run all summer you may not have gorwing molding. The AC will keep the RH below the threshold that mold will grow. Cleaning the ducts will improve the air quality as the inside or air duct are usualy pretty nasty. . The duct work can be fogged with sporicidin, an anti microbil that is used in operating rooms and food processing plants ,etc. It has about a 6 month residual effect.

    If you are not familiar with UVC lights do a little research on them. American Lights makes a good quality light and has information on thier website. Furnace filters have a limited role in keeping the air clean. To restrictive of a filter reduces the effficiency of your HVAC system by 30% or more, You will pay a lot to operate this way. If you are looking for better air cleaning than get a room air purifier. It will have a HEPA filter and runs 24 hrs a day verus the on off of the furnace. I like the Austin Air brand.

    I would resist the urge to move the HVAC to the attic as it is not energy efficienct. You would be better off spending that money on keeping the basement dry and insulating the basement walls.

    Most issues with wet basements are caused by improper grading and not controlling the discharge from gutters etc. It sounds as if you have a plan to control ground water. This should be a tremendous help in controling moisture in the basement.

    Moisture in basement have 2 causes. First is water that leak into or wicks through the concrete. Again, it sounds like you are adressing that. The next source of moisture is from air leaks. One of the biggest area of air leaks is from the sill plate and rim joist areas.

    If you can get the basement mositure level down and seal the air leaks then there will be no need to move the HVAC.

  4. GBA Editor
    Martin Holladay | | #4

    Q. "What is my biggest problem?"

    A. It's a toss-up: either the high grade on the exterior of your house, or the fact that your two favorite rooms lack a real foundation.

    Q. "How do I start?"

    A. Hire a contractor to improve the foundation of these rooms (or demolish them). Then lower the exterior grade, slope the grade away from the house, and install perforated drain pipes to drain soil moisture to daylight at a location far from your house.

  5. user-1030353 | | #5

    Thanks, guys. I figure we will address the "lacking foundation" issue when we do our big renovation (we were hoping to push it off for 2 - 3 years... but it might come sooner). I always planned on tearing off the "owner-built" parts, and rebuilding to code. I have some family members coming forward with the cash for the sitework, so that will probably be my big project through Christmas. From a green standpoint, is it possible to keep the house "safe", livable and mold-free without doing the complete rebuild immediately? Can I control major humidity issues with a clean HVAC system and dehumidifiers? Is there something else I SHOULD do?

  6. BobHr | | #6


    You are more likely to see mold outside the duct work. In the summer you the air passing through the ac coil and removing the humidity. In the winter you have heated air.

    The Furnace system is more likely to distribute dirty air from the basement because of leaky return ducts. Seal up the ducts for energy efficiency and air quality.

    The basement is going to play a role in air quality whether you have duct worki in the basement or in the attic. Dirty air in the basement is a sign of other conditions. These condition merit repairs for the soundness of the sturcture.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |