Basement / Discussions

How to deal with condensation in basement?

...basement is finished? Finishing a basement in a cold climate like Minnesota requires careful management of the "dew point" to prevent hidden mold (see here to better understand the dew point in homes.) Since you plan to keep the existing vapor barrier against the concrete, the biggest risk is moisture getting trapped b...

Posted by Shane Hu Aug. 7, 2025 Basements improvements 1 response

How to properly insulate rim joists embedded in concrete in a home built in 50s?

...basements, and poses exactly the risks you are hearing about - that insulating them can trap moisture and cause them to rot. There are pages here about how to finish basements - How to insulate basements properly without causing mold or rot We are of the opinion that the heat loss is preferrable to rotten joists, so I ...

Posted by GP Mitchell May 30, 2025 Foundation and basement improvements 2 responses

Crawl space versus slab, which is better?

...basement with ICF walls is a far better way than the mold-inviting normal practice of trapping moisture in basement walls with a vapor barrier. A crawl space is a just a short basement, so if you did it with ICF then kudos to you for a good design, but in general we find the very notion of a crawl space a bad building ...

Posted by Doug Bennett Jan. 5, 2025 Foundation and basement improvements 1 response

Why is there condensation in between 1.5" polyiso board and roxul insulation?

Hi guys im from Canada and I recently finish studying and insulating my basement. I used one and a half inch polyiso board insulation glued to the wall with adhesive and I left a half inch Gap all around the board to spray foam. In front of the wall I frame to buy for walls and insulated with Roxul insulation Batts I w...

Posted by Tyler Norrie Feb. 9, 2021 Basements improvements

Is there anything I can do about a vapor barrier on the wrong side of a basement wall?

...basement. You may have seen this page but others reading may not, but this article is about what is going on in your walls – Why basement walls go moldy and how to build basement walls that will stay dry At this point it sounds like the damage is done, but you may be able to buy yourself some time before doing a major ...

Posted by Iain B Feb. 8, 2021 Basements improvements 8 responses

Do I need to spray foam the ceiling of my crawl space to help winterize it?

...basement from the inside using an internal perimeter drain.    

Posted by Sheilagh Thompson Jan. 21, 2021 Crawl spaces 1 response

Why is there condensation above ground on an interior basement wall?

...basement and installed 1 inch foam insulation to the exterior wall before framing and then installing fiberglass insulation. When he began drywalling he noticed moisture behind the fiberglass on the secrion of the wall that is above ground. At this point we are wondering what we could do to remedy this. I should mentio...

Posted by Barb Daluisio Jan. 12, 2021 Basements improvements 1 response

Which is the best basement ceiling insulation?

...basement ceiling/first floor of my house is insulated with 3 1/2" faced fiberglass with the vapor barrier on the house side (not pointed downward toward the basement). I want to had additional insulation, especially over the unheated garage. Is wool insulation over the existing fiberglass recommended, or should I simpl...

Posted by David Boone Jan. 9, 2021 Basements improvements

Is there any risk to a concrete foundation from adding interior insulation?

...basement because it could cause freeze-thaw damage to the foundation. Their stance was that these old houses like to "breathe" so it's better to avoid any changes because it's lasted this long as-is. I want to follow the "Why are basements moldy" recommendation of rigid insulation board directly against the concrete an...

Posted by Drew Tozer Jan. 5, 2021 Basements improvements 9 responses

Can you insulate a concrete block basement walls with only rockwool?

...basement ourselves (zone 5, Toronto) and on a budget after gutting the entire finished basement due to extensive moisture penetration and mold issues. The foundation/walls are concrete block and we have 2 sides done with interior plastic membrane to french drain and sump pump, one side exterior waterproofing, and one s...

Posted by Aarne Valikangas Jan. 1, 2021 Basements improvements 1 response

What's cheaper for total building costs, slab on grade or basement?

...basement for TOTAL cost. While i know SOG is cheaper than basement, i can do 750 sq ft on top of 750 sq ft basement with finishing in two years after concrete dries vs about 1200 sq. feet with SOG to accomodate our total needs. So my question is: is a 750 sq ft house on top of 750 ft basement cheaper than 1200 sq ft ho...

Posted by tony wolff Dec. 24, 2020 Foundations and Basements 1 response

What is the best way to do a basement renovation?

...basement and wasn't sure if the tar paper even really did anything or its an old practice the contractor was used to doing? Basements are often moldy, and unfortunately even after basement renovations are completed because people usually rebuild them in the same way, which would meet Einstein’s definition of insanity –...

Posted by BIG FOOT Nov. 18, 2020 Basements improvements 1 response

What is the best way to stop thermal bridging between my ICF block construction walls and my footing?

...basement you can include ThermaSill insulated door threshold forms. If you've been through our site at all looking at foundation options then it would be no surprise that we aren't big proponets of basements, so if we were to build one, this is how we'd do it for performance and to eliminate the risk of mold. Below is ...

Posted by Walter van den Broek Sept. 18, 2020 Foundation choices 1 response

Could we use a raft slab with ICF walls on a sloped site?

...basement on problem soils A raft slab is engineered to spread the weight of the building evenly over the entire surface of the slab, so there is no footings needed, and no, its not going to go anywhere when done properly, and a perimeter skirt insulation is added to prevent frost heave. So what you may be able to do, ...

Posted by Paul Fischer Sept. 15, 2020 Slab on Grade 1 response

Can basement walls to dry to the inside with foam board?

...basement foundation walls. From all of my reading it says that your basement foundation walls can only dry to the inside. If I put foamboard on the concrete and seal it everywhere, when moisture comes through the concrete it will have nowhere to go. Perhaps I am missing something here but seems to me over time behind t...

Posted by Tim Hanrahan Aug. 20, 2020 Basements improvements 7 responses

The thickness of vapor retarding latex paint - Is measurement wet or dry?

...basement floor and would like to know if one coat is thick enough.  The thickness cited in an ecohome article was 0.00031. The technical data for the paint has a wet thickness that matches the article but a much smaller dry thickness.   When we used a vapor retarder primer (vapor barrier paint) in our Edelweiss LEED Pl...

Posted by Kim Boas July 24, 2020 Basements improvements 3 responses

How would I rectifiy problem of foundation wall cracks with finished basement?

...basement, with tar paper against the cement wall, then studs and four inches of batt insulation and then a vapour barrier and drywall. Two years ago I noticed cracking on the exterior of some of the foundation blocks, where the interior walls had been insulated but not on a portion of the basement walls that were not f...

Posted by Terry P July 22, 2020 Basements improvements 3 responses

What is the best flood prevent system for a home?

...basement floor The best way to prevent flood damage in basements is with proper drainage and sump pumps, but I suspect you may specifically be referring to sewage backup. To be clear - are you hooked up to municipal sewers or do you have your own well and septic system? Give us a few more details if you like and we may...

Posted by Dawn Wlezien July 15, 2021 Waterproofing and drainage 2 responses