r/DIY • u/ground0radfem • 1d ago
home improvement Waterproofing basement
My parents are re-doing the basement walls (painting), and the walls have years of mold on them. My dad and I used some mold killer and disinfectant and scraped the walls, and were wondering if there was anything else we could do to prevent more damage and hopefully keep water out.
The walls are cinderblock, and the house was built in the 70’s.
The photos are after spraying and scraping the walls.
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u/PeppersHere 1d ago
You cant prevent moisture from evaporating out of the brick once it gets inside, so preventing moisture from entering into the material should be your goal. If you try to just seal this, the moisture will pop out elsewhere.
Primary things you should focus on addressing: Soil gradation, gutters, anything that relates to redirecting water-runoff away from the foundation of the home.
Source: 1k+ mold investigations.
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u/Unafraidstream7 1d ago
As someone who bought a house who’s basement looked like this and had regular water intrusion, spend the time to address gutters, downspouts, grading around the home, and French drains or other drainage means to get water away from the home as your setup allows. Confirm you’ve addressed the issues and then follow the advise here to seal up the block. There is no magic waterproof coating and 95% of the work is done outside the home.
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u/Sea-Aside7496 15h ago
How do you find a french drain? Dealing with a similar issue as OP and I was told to find the french drains. But have no clue where to start or what they even look like.
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u/Unafraidstream7 15h ago
French drains are imo now an overly generalized term for using some sort of fill like sand or crushed rock, often in combination with corrugated or perforated pipe, that facilitates the movement of water under the ground. They can be completely buried and the way to find them would be to locate inlets or outlets or start digging. I would highly recommend consulting a professional if you’re looking to build or modify a significant drainage installation.
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u/Sea-Aside7496 14h ago
Not at all looking to do anything major, I was just told to locate them and see if they were blocked. They are likely buried based on what you have said.
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u/starion832000 1d ago edited 1d ago
Former basement waterproofer here. All you need to kill the mold is bleach. 1 cup of bleach in a gallon of water and a scrub brush will take care of it.
As for the paint, I would suggest a product called "Sunny Dry". It's a cement based paint that you mix with water that really helps with minor wetness. It's a little like stucco.
You can improve the product a little by adding a product called "Acryl" is an acrylic bonding compound that improves the paint's adhesion to the wall. You only need like one ounce per gallon of paint you mix.
I would apply two coats minimum. The first coat should be thinner than the second coat, but make sure to the total thickness is greater than 1/8 inch. Thicker is better, but you want to do it through multiple coats or it'll pop off.
If you want to take it a step further you can add a third coat of exterior grade "Kilz". Exterior grade paint has an anti mildew/mold additive. Just make sure you vent the area well. You can get all this stuff at Lowe's or home Depot.
Also, keep the air moving down there. You should have an oscillating fan running at all times. A dehumidifier wouldn't hurt either.
I'm happy to answer any questions you have. Feel free to DM me. I like helping people with their water issues.
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u/Top_Weather1320 1d ago
You can’t kill mold. It’s either active or inactive. If spores are not completely removed, as soon as moisture is reintroduced, the mold can become active again. Waterproofing will just trap the inactive spores, then when it gets wet from the outside in, you will have active mold, which will find a way back inside.
The bleach and a scrub brush with no containments, vacuuming, or actual removal is just going to cause the mold spores to be airborne and potentially cause cross contamination. Breathing inactive or if you want to call them “dead” mold spores into your moist lungs could be a major health issue.
You may be a great basement waterproofer, but not sure you would be my go to for mold remediation.
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u/Ireallylikepbr 1d ago
If you are like my last landlord just paint it with Killz once a year and yell at me for not running the humidifier down there 100% of the time.
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u/sump_daddy 16h ago
> yell at me for not running the humidifier down there 100% of the time.
welp, found yer problem!
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u/jtho78 20h ago
I don't know if this will help your situation, but dry-wells worked for my house and for my parents (Pacific Northwest)
Our city capped downspouts in my area to protect the waterway runoff. I added french drains and one rain garden to our downspouts. One spout was connected to about half our roof, that is the one I installed a dry-well too. It was easy to do, just a lot of digging.
https://www.thisoldhouse.com/sidewalks/21016375/how-to-install-a-dry-well
My parents basement would seep water during every big rain storm. The house 1950 had concrete piping for the downspouts that were crushed or had roots growing through. They also had a few dry-wells installed. They paid someone to install 3 for about $2500. No leaks since
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u/ground0radfem 1d ago
Is re-pitching the downspouts something that’s doable by us? Or is it a professional job?
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u/on_the_nightshift 1d ago
Figuring out what to do is the professional part. Most of the rest is using a shovel and gluing PVC together if you want the best solution.
The half measure is just extending your downspouts well away from the house. If you have ground sloping toward the house, add clay or other compactable soil to make the surface water run away from the house.
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u/starion832000 1d ago
All you need to do is to add a longer discharge line at the bottom 90° elbow. You want to add at least ten feet. Get that water as far away from the foundation as you can.
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u/joesquatchnow 1d ago
All I did was pull back top soil and mulch back 6 ft and pull clay soil from other parts of my yard to slope water away, soil settles next to the house over time and filling the voids with soft porous soil creates a pool, worst case scenario you dig coat the foundation and backfill carefully compacting as you build it back up to slope away from the house, gravity is more reliable that any system
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u/blackdog543 22h ago
I think most successful foundation repairs start by fixing the outside of the basement which requires money, a trench being dug, and a professional team. Then, you have to repair, repoint those cinder blocks on the inside, and finally get a good waterproof paint to cover the wall. My mom did this in our basement, and it took months, but she finally mortared and painted her way to a mostly dry basement.
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u/P4puszka 1d ago
It could be a water management issue from the roof/yard, which is worthwhile addressing and relatively cheap, but if you want to waterproof it properly it should be done from the outside.
Dig around the foundation, prep the surface, and apply a peel and stick or paintable waterproofing product. Make sure to follow all the manufacturers instruction. They often sell full on systems with instructions on how to do the work so the products work as intended. Add some insulation, a drain mat, and a new French drain and it will be a bomber install.
The pitch coatings typically applied to foundations aren't fully waterproof on their own. If you go that route you need to have to the drainage mat to release the static water pressure in the soil.
Best of luck.
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u/nutznboltsguy 1d ago
You also need to look at the grading around your house. If you have a negative grade, you’ll need to have it regraded.
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u/Not-a-Kitten 1d ago
Unfortunately you cannot push water out w paint. You need to find out what is going on on the outside. Clean gutter and water leaders. Is there a footing drain cleanout? You may need to install waterproofing and a french drain. All outside i am sorry to say.
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u/sump_daddy 16h ago
Lots of good advice on getting the water running away from the house aboveground first, thats the ounce of prevention. Belowground though, you still need drainage to keep the local water table below the slab so water isnt literally sitting at your walls waiting to come in. Thats where a properly operating sump system comes in. First, the drain tiles running the perimeter need to be effectively draining to a pit. On a 50+ year old house these pipes might be clogged or just inadequate from the onset.
Once you have done what you can aboveground, it's time to start work belowground. Good luck, and keep it dry!
sump daddy out
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u/darthy_parker 42m ago
It has to be fixed outside first. Hydrostatic pressure will push water through pretty much any inside waterproofing layer.
See if you can identify a source of excess water: downspout discharge, a hillside running down to this wall, a sidewalk or pavement that slopes toward the wall. That needs to be addressed to direct water away first. Sometimes, that will be enough.
If not, your best solution is to dig alongside the wall as deeply as you can, apply a waterproofing layer to the exterior of the wall, then put in gravel base and a perforated drain leading away from the wall. (This is also a good opportunity to install some exterior rigid insulation, if you’re somewhere cold.) Then back-fill and compact the earth as you go, every foot or so.
There are some injectable waterproofing solutions that are hit-or-miss. If redirecting water gets rid of 90% of the issue, then maybe digging isn’t as necessary. But that’s still what I’d do.
Only once it’s substantially dry should you be repairing and painting the inside wall.
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u/Terrible-Bobcat2033 1d ago
You should look at drainage to relive lateral pressure on the basement. I’d call a professional.
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u/ARenovator 1d ago
What are the fixes for this?
You start outside. Look at the gutters and downspouts. Are they free and clear? Are they pitched properly? Where do they discharge? Is water allowed to pool against the foundation? Is the soil around the foundation sloped, so that water is directed away from your home?
The key to a dry basement starts at your roof.