Looking for advice from basement experts: What should I do with the concrete block in my semi-finished basement?
Asked by Selin Duval 
6 months ago
Last Updated: May 13, 2024
Hey, anyone here know about basements? We just moved in a few months back and I’m thinking about partially finishing our basement. What’s your advice on what I should do with the concrete blocks – seal them or leave them as they are?
After a lengthy online discussion, I finally figured out that if it’s an exterior wall, I had to choose between spraying foam or leaving an air gap. I ended up going with non-faced insulation
I decided to keep mine uncovered to allow it to breathe, then I covered and sealed the wall with Ridgid foam board before framing it. This allows moisture to drip or seep to a sump pump between the concrete and foam board. Sealing the concrete could lead to issues in the future
I like to keep the block visible. We used Drylok to seal it and added a drywall mud/silica sand texture on top.
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Hey, that tee at the bottom definitely needs some fixing.
Nug Get oh yeah, there should not be a cut there, but it’s only for the laundry 🤷🏻♂️
Put a coat of Drylok on it and then add rigid foam board
Then we put the Drylok, followed by the ridged foam board, and then the wall form.
You can just leave it as is. If there are moisture problems, they should be addressed from the outside. And there’s no need to insulate either, since most of the coolness in a basement comes from the slab.
Make sure you use at least 2 inches of closed cell spray foam. Hopefully the studs are pressure treated or have a gap between them and the wall. Closed cell foam not only increases structural rigidity by over 300%, but also acts as a vapor barrier and raises the block’s value to about R21. Once that’s done, put up your wall board and you’ll be good to go!
I suggest leaving it as is. If there are water issues, address them from the outside rather than the inside.
I recommend using a product called insofast. You’ll thank me later.
: I checked them out. They seem really interesting. Have you had any experience with them previously?
J.S. Fray: Oh, I’m a contractor and I always incorporate them into my basement remodeling projects.
If it were me, I would have applied dry lock before putting up the framing. But now that it’s up, you can use insulation boards by sliding them behind the framing and taping them together.
Had some wall paneling up that I decided to take down and inspect before starting my project
Hey Jon, you can still drylock, it just requires more effort to work around the studs.
Finish it off with drywall.
Make sure to seal, insulate, and finish it properly.
For now, I would keep it as it is and make sure the basement stays dry.
Foam insulation goes hand in hand with drywall
I used a waterproof primer specifically designed for cement blocks when I painted
Closed cell spray foam insulation is great for sealing up any gaps
Start by removing the studs. Next, apply Drylock to the walls before dealing with any issues of water penetration from the outside like gutters. After that, install Owen’s Corning pink board FOAMULAR NGX F-250 2 in. x 4 ft. x 8 ft. SSE R-10 XPS Rigid Foam Board Insulation over the Drylock walls using foam board glue. Then, tape the seams, reframe, add a 6mm moisture barrier, and finally, install the sheetrock.
I believe you were referring to the 6 mil moisture barrier.
Before anything else, check for any leaks during rainy days! We initially drywalled our basement but later discovered leaks at the bottom. We removed the drywall, fixed the issue, and installed exterior siding. Finally, we painted it and now we absolutely love it.
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Actually, had a pretty smart idea. I never would have guessed.
No matter what, make sure to seal it properly
Country Home Building: Do you think drylok would be beneficial or could it potentially create more problems?
Everything should turn out okay
Recommends drylok for assistance
Avoid painting or sealing the block. Install rigid or fiberglass insulation, followed by a vapor barrier and then drywall.
It might be a good idea to confirm with your local town regulations, as some towns have specific requirements.
There are styrofoam products available that can be installed between the foundation and drywall for reinforcement. It’s unsure if they are necessary, but they can strengthen the drywall.
Insert dimple board into a French drain.
I always recommend dry lock paint to my customers. It’s more effective to prevent rain or leaks than risk saving $50 and dealing with water damage behind the sheetrock.
Absolutely, I agree. My neighbors experienced the same thing and had to redo all the Sheetrock.
Apply dry lock on it
Consider using polyurethane foam spray, check it out to see if it suits your needs
Take out all that framing and switch it with metal track and studs 👍
It appears that water is seeping into the brick. One solution could be using 3” hard foam sheets and tar on the exterior of the foundation bricks to improve drainage. You might need to excavate around the foundation to create a positive drainage flow away from your home.
Making assumptions from a photo of a seemingly dry block wall is not very accurate lol
Haha I totally agree, thanks! 😂 I don’t see any evidence of water leaks either.
Seeing efflorescence could mean there was water seepage at some point, even if it looks dry now. It’s a sign of drainage problems.
You’re absolutely right. If you’re familiar with it, you’re familiar with it, isn’t that right! I used to be the warranty manager for a national home construction company that completes more than 400 homes annually. I encounter this regularly, it’s part of my job!
Great job, !
I apologize for the length, but you asked a significant question. Firstly, live in the house for a full year and take notes. Traditional sealers like Drylok won’t solve water issues. Try taping a 3’X3’ clear heavy plastic sheet on the wall and floor. Leave it for 72 hours to check for condensation or darkening of the concrete. Efflorescence on cinder blocks indicates a moisture issue from ground water or moisture seeping through the blocks. Monitor temperature and humidity levels in your basement and upstairs for a few months. Check if the basement humidity is consistently above 50%, which could lead to mold. It takes time to accurately assess the situation, ideally a year. Discover the problem areas before considering basement finishing.
Hey , I appreciate all the info. I’ll make sure to look into it!
Hey Jon, I understand it may not be what you were hoping for, but in the end, it will benefit you to have a safe, mold-free home. Best of luck to you.
Great job, ! I totally agree with all of your points.
The first step is to tackle the moisture issue; otherwise, it will keep coming back.
I used ThoroughSeal to seal mine. Make sure to patch up any visible holes first.
Seal and insulate it
You notice a lot of efflorescence on that wall. It seems like there might be some moisture problems. I recommend starting with relocating or extending downspouts, correcting grading, and possibly looking into a waterproofing system. Basements are prone to moisture problems, it’s not a matter of if but when. Take some time to observe the situation during rainy and damp conditions to identify the areas with moisture.
Following
You can purchase a thick liner to conceal it in that area. Typically, the liner is placed under the floor where a French drain is located. If there is a leak, the water will be directed towards the sump pump. Check for leaks while it is exposed.
Consider applying dry lock to the wall. Insulate using Pink Foamboard for effective insulation.
I wouldn’t recommend adding a moisture plastic barrier. It’s best to let the air flow to prevent mold from forming due to trapped moisture. Consider sealing the bricks with rubberized paint and using green/blue board for Sheetrock. Make sure there is proper air flow in the space. If you ever encounter a moisture issue, invest in a dehumidifier. Look for one with a pump for easy water removal. Check the machine once or twice a year to ensure it’s functioning correctly. No need to remove the studs just to paint; you can easily reach in. If you notice water seepage, inspect your gutters and consider installing a French drain. It’s a DIY-friendly job. I would also suggest adding electrical on that wall. After reading multiple responses, some seem to be suggesting unnecessary extra work.
Let’s do a moisture test and observe the results. Adding plastic to block surfaces can create more moisture issues. Consider cavity vents in walls with higher moisture levels and traditional lumber framing to avoid complications.
For anyone thinking about using drylok…
Check out this video: https://youtu.be/pgA7FqD2IR8?si=MlZHrcfnjS9d_Dha
Basically, you’re just sealing in moisture in the block, which is not good.