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

Questions before buying a home involving crawlspace, roof, outbuilding, and mold

ChrisInIllinois | Posted in General Questions on

Hi, I am chris, I live in the hot and humid southern Il. Trying to get my self In to a home, but need to find out how to keep my family safe. TBH I am scared of all that I have learned about this area and how it wrecks the attics and crawl spaces with mold, rot, and fungi.

Thanks to many articles, input from people on this site, and my home inspector I have learned a great deal of info about homes I never knew. So much in fact it is making picking a home hard. I am at the point of making an offer yet again, but trying to figure out what i’m getting my self into.

Martin Holladay, You have helped me a lot does me becoming an GBA prime help you at all? If not is there any way to buy you a beer, coffee, dinner?

Lets get to it:
The home is 980~ sq foot 2 bed room looks nice built 1975. Has small old single pane wood windows need re glazed, but no rot or paint.

Has an out building 16×24 on an concert pad that is partially finished (dry wall on ceiling and walls). The out build had a roof leak, can see where they patched the roof, has ceiling damage and a strong musty mildew smell. The walls look fine even at the cement floor. Based on some work I have seen I’m not sure if codes where followed when out build and carport was made.

On this outbuilding:
Is there a way to check if the concrete has foam or plastic under it before I make an offer?
Is there away to check if the sill plate has its gasket or is made of pressure treated wood? siding and drywall are hiding it.

It one room to small, I can make do for now using living room until I get an add on or fix the out building.

Mold issue in attic: ( I got up there to see)
It has been disclosed the home has had mold issues in the attic. It is a small space (maybe 4-5ft high max) 36’x24′. based on google maps (2013) it only had gable vents. The mold company said mold was due to inadequate roof ventilation.

Now near the ridge there is 4 vents installed. the ones that give ~50 square inch of air each, but there is no soffit vents, and the bathroom is still vented in the attic :(. From my understanding this is not enough free moving air. It has been treated I see the antimicrobial on everything. Only mold I see looks to be in one spot due to ice damming.

Crawspace and Roof:

Based on The humid climate 62812. I am not sure What I need to do to address the roof and crawlspace. Crawlspace encapsulation Vs Ventilation with vapor barrier. Roof add more ventilation or encapsulation. I know this has two sides, I am just trying to see how much I will need to spend to protect my family and investment.

Since there was mold/ is mold after this is fixed should the HVAC ducts be cleaned or replaced? The HVAC system ac is new as of 2014 but duct are old untouched.

This is the nicest looking home I have found in my price range that meets all but bedroom requirements. Its cheaper as its 2 bed rooms. It will leave extra money to work with each month.

If I do go with this one, any tips on things I should have done before I get my kids in there, outside of of fixing the mold? like HVAC duct cleaning, air testing, etc.. I do plan on pulling the wall out very quickly for rock wool insulation, They are paneling  when I knocked it sounded hollow, so I think no drywall/plaster.

Thanks, Please advise.

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. Expert Member
    Peter Engle | | #1

    Hey, Chris. Pretty lot - It sounds like you're on the right track. You've got a lot of questions, and you're just going to have to keep researching and learning.

    Don't worry about whether the outbuilding was built to code. Even if it was, those codes just don't apply any more. You will probably have to do quite a bit of work to make this space livable anyhow, and code improvements are just a part of it. It won't have any foam under the slab. It probably doesn't have any plastic under the slab. It might not even have foundations under the slab. The only way to find out is to dig down around the outside to explore the foundation, and drill some holes through the slab to look for plastic. Same with your sill plate questions. Take off some drywall and look. Drywall repairs are cheap and easy.

    As far as the crawlspace goes, you didn't really tell us what your home inspector said. I'm guessing that it is damp/wet down there. Dealing with it is your first course of action, as it will impact everything else. There is a good chance that moisture in the crawl is the reason your attic is getting moldy as well. There are great resources here at GBA on how to dry out and treat your crawl space. For most climates and conditions, I prefer closed, insulated and conditioned crawl spaces, but that's just a preference. You can successfully do vented crawlspaces if that's your preference.

    You should at least clean your ducts. You should probably be prepared to replace your ducts. You will know within the first year whether the HVAC system is really working for you. Clean them now, and see whether you've got to make changes in the future.

    In general, deal with moisture issues first. They are the most important to the long-term health of the house and your family. Water leaks are urgent and demand immediate attention. Dampness is chronic and should be high on your list. HVAC gets more important as winter approaches, and you should at least get on a contractor's schedule before the weather starts turning colder if you've got heating issues to address. Stripping out the walls to insulate can be tempting, but it opens up a can of worms, and with winter coming, it might not be best to have a naked house to live in. Sometimes it's best to spend the winter studying, learning and planning so you're ready to hit the ground running in the spring.

    Oh, and good luck.

  2. walta100 | | #2

    I think no out building built in 1965 had plastic or foam under the slab. My guess is the slab is on dirt no gravel base.

    As far as the attic mold I would like to see the same or more square inches of soffit vent than you have in ridge vent and get the bath fan vented thru the roof.

    Make sure your inspector provides you with photos from the crawl back of the space not just what you can see when you stick your nose in the access panel.

    In most cases duct cleaning only cleans people’s wallets.

    I think pulling out the walls to insulate with rock wool is a poor investment and likely dangerous as walls and trim are likely covered in lead paint that will become air born dust if disturbed. Blown in cellulose is generally more cost effective.

    If the home is on city water I would want to know if the pipe going to the house is steel lead or copper. If on a well I would want a report for bacteria and lead arsenic ect general you will have a local lab for bacteria and mail order for the other.

    Now is a very scary time to buy Illinois real estate. If the democrat governor is elected, all real estate will almost certainly face a 10% tax that will drop the value 10% over night.


  3. Expert Member
    Dana Dorsett | | #3

    The mold issue in the attic is almost certainly due to venting the bathroom into the attic rather than outdoors, plus other air leaks through the ceiling from the conditioned space into the attic space.

    The four roof vents are an attempted band-aid to the attic moisture problem(?), but don't do much, as you have surmised. The original gable vents would most likely be fine if the bath was properly vented and the ceiling plane air sealed on all electrical, plumbing, flue, duct penetrations. (Hopefully there are no air handlers or ducts in the attic?)

    In your climate (zone 4A) a vented crawl space usually brings more moisture into the house than it purges. If there are heating or AC ducts down there it's both a house & HVAC efficiency problem. Duct leakage and room to room pressure differences from even minor duct imbalances will use "the great outdoors" and the crawlspace for part of the return path. It's also far more difficult to air seal between the crawlspace and first floor than it is to seal at the foundation walls. It's better on all accounts to put the crawlspace inside both the pressure and thermal boundary of the house.

    DON'T spend any money on increasing the attic ventilation. That will only depressurize the attic further drawing more conditioned space air into the attic. The first order of business would be to vent the bathroom (and anything other venting into the attic) to the out doors.

    Then AIR SEAL!!!

    The priority order on the air sealing in a heating dominated climate (that's you) is :

    1> air seal the between the attic and conditioned space below. Get serious about it, including weather stripping the access hatch(es).

    By sealing the top of the house it blocks the top of the "stack" in "stack effect drive", which draws in outdoor air into the house 365 days/year whether it's windy or not.

    2> Air seal the bottom of the house which means the crawlspace walls, or between the crawlspace & first floor.

    The bottom of the house seals the bottom of the stack effect. With both #1 & #2 taken care of the other air leakage in the house hardly matters, and the amount of stack effect air leakage pulling humid conditioned space air into the attic, and pulling humid summertime air into the crawl space is dramatically reduced.

    Then monitor the humidity levels in the attic. If the humidity levels remain high (not likely), close the gable vents, and add soffit to ridge venting. Be sure that the soffit venting is more than half the total free air area of the total- something like 60% soffit area, 40% ridge vent area. When the soffit area is bigger the ridge area the stack effect drive only goes as high as the soffits, and there is effectively no stack pressure difference between the ceiling below and the attic space. If the ridge vents are bigger the attic is depressured relative to the conditioned space most of the year, which will pull more air in from any remaining air leaks through the attic floor.

  4. GBA Editor
    Martin Holladay | | #4

    Q. "Martin Holladay, You have helped me a lot. Does me becoming a GBA Prime member help you at all? If not is there any way to buy you a beer, coffee, dinner?"

    A. Becoming a GBA Prime member does not help me financially in any way, but it helps pay for the GBA site, which is a good thing. (If the site doesn't break even, I wouldn't have a job.) So subscribing is good.

    I agree with the advice you've been given so far, except when it comes to duct cleaning. Duct cleaning is usually a waste of money.

  5. ChrisInIllinois | | #5

    I have not payed for the inspection on this house yet, once I'm I know what I am getting my self into I will make an offer, contingent on inspection.

    lead and asbestos:
    Theres not much paint in this home most wood and paneling. I thought I was out of the woods with lead paint / asbestos around 1975, just to keep an eye for some stuff.

    Duct work:
    The return is in the attic, based on HVAC books I have my nose in I maybe running a return to each room.

    The duct work is in the crawlspace, It is leaking as when I opened it up I got hit with the cold air from it. There is no vapor barrier. So no telling whats growing in up under there.

    Duct work cleaning-
    My thing with duct cleaning was if the mold spores had made there way into them.

    The out building:
    That is about what I was thinking with the out building, Was contemplating making it the 3rd Bedroom for my teenager / turn into small apartment when he goes to college to save on his housing cost. I was thinking to make it live-able would cost around $8k-$10k, If you don't think thats High enough, I may have to reconsider getting this house, or get a idea of cost of small add on for a room.

    in the photo you can see the outbuilding.

    My understanding of rockwool is its a much better product, friction fit helps with air sealing, r- value not affected by water or compression, best fire rating, and sound deadening. Do you feel this benefits are not worth the cost (willing to change to a different insulation but they sold me with its pros)? Plus I get first hand look at walls for mold issues and can air seal.

    Homes in the area:
    houses In this area in my price range Up to $100k all have the same issues, age makes foundations and sewer pipes bad. climate and lack of building science for the age makes roof's and crawspace/basements not to safe. Lack of money for up keep so gas furnace are replaced with baseboard heating or electric furnaces.

    This one had its sewer replaced out to the main with pvc 3 yrs ago, seems one less thing to worry about.

    Based On what I have seen my Todo list should I take this house is Or any other it seems:

    Fix the mold issue

    Fix roof ventilation Or seal it up.
    Add gutters, soffit vents if need, pull up first few feet of rake shingles replace any bad boards and install grace and ice water shield. Vent bathroom vent.

    Install kitchen hood vent
    Air seal, learn about if I need mechanical ventilation.
    replace paneling with drywall and update insulation.
    Add attic insulation to correct level.

    Install new siding with foam, Old siding has spots in issues paint covering where the skin had been chipped away and water got to it.(small sq should not be too much)
    Crawlspace Fix ventilation or seal it up. + vapor barrier.

    windows (there are only 10)
    low-e storm windows
    Re-glaze windows
    find out how to care for wood windows that are not painted.

  6. walta100 | | #6

    In the photo the siding looks to wide to be wood. 1965 seams too new to be asbestos and too old for hard board what is it made of? Why are the plumbing vents so tall?


  7. Expert Member
    Dana Dorsett | | #7

    On the "to do" list, air sealing the ceiling plane/attic floor and the crawlspace would be way ahead of insulating.

    If the supply ducts are in the crawlspace, why/how is the return in the attic? Where is the air handler/furnace located? The last thing you want to do is to punch a return for every room through the attic floor, unless you bite the bullet on the expense of sealing the attic and insulating at the roof. Ducts in the attic outside of conditioned space and making holes in pressure boundary at the top of the house increases the amount of infiltration losses, and risks putting more moisture into the attic. Minimize the number of penetrations into the attic (and seal them), don't add to them. With a one story house single common return in the more open parts of the house and using partion walls as jump-duct returns usually works just fine.

  8. ChrisInIllinois | | #8

    Walter Ahlgrim: The home was built in 1975, It seems to be hardboard/pressboard. the area that has been damaged with the "skin" removed in like 3 inch section looks like OSB that has been painted, but it is siding and not the house sheathing I was seeing.

    Dana Dorsett: The to do list is in no order, First thing I plan to do is remove insulation out of attic (there is only fiber bats and not much, with mold up there on the decking thats been treated with a new spot growing, I assume a few dollars of wasted insulation to make sure all spores are gone and fixing moisture issues will be money well spent), attend to any roof venting/ penetration problems/ mold issues, Then seal up the ceiling from the top.

    As far as air balancing and returns go, I'm still learning about this It may not need anything, it might just need some wall vents cut at the top of the hall wall, maybe some other procedure I have not seen yet. There is a Hall that has all bed rooms, bath, laundry/air handler/hot water heater room, leading off it the return in located in the middle of it about middle of the house. Its only like 4' of duct.

    I am not one to just jump in and do something after very little research. If i get knee deep and a Issue pop up I don't freak and just make it work, it the project gets postponed until I learn to handle the issue correctly :).

  9. walta100 | | #9

    You may want to be sure you understand what is going on with the siding as most brands are under recall and if a past owner has claimed a settlement for this home.


  10. ChrisInIllinois | | #10

    Thanks Walter, If I get this place, I was just going to reside make sure house had wrap and then put up foam board assuming its not done. I will look in to this recall stuff.

    My main concerns for this home as it is, are the mold, mold treatment, steps to make sure my kids will be safe from mold (i have a 3yr old) (cleaning ducts etc what every needs done) as well as the adults . Then the adding space via the outbuilding for a 3rd bedroom. I don't Want to walk away from this house, its on a dead end so no traffic, it in the "city/town" but down a road far enough it feels country/rural and the price is hard to beat. I just am not ready to pay for a 3rd home inspection, The other 2 had issues I had to walkaway from for a first time home buyer /w kids.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |