There are some things a home owner has to do that are boring, dirty (not in a pleasant way) and don’t have much visual appeal. My first experience with this was roof reshingling the roof. Thousands of dollars and a lot of banging (not in a pleasant way) later, there was the new roof, same as the old roof, only smoother. Sure, the new roof will keep the water out but appreciating that takes a bit of abstract thinking, especially when the impact of a leaky roof can be hidden for years.
My latest project is overhauling my unfinished, mouse-infested, and slightly damp 100 year old basement.
All the working parts of a house are in the basement. Electrical, plumbing, structural support and heating systems all start there. An old house has lived through many changes in philosophy or technology in these systems, shifting through copper and lead plumbing, knob and tube wiring, hot water heating to forced air, adding air conditioning, insultation, extra rooms, floors, and other changes. Updates are manoveured into a structure built for other times. Add to that what’s happened outside the house: cars, driveways, climate change and elaborate landscaping including deck building and an older basement is under a lot of stress.
I’m aiming to remediate my basement, making it as sound as possible. To do this, I’ll put to good use a course I took over the winter on home structure.
There are five types of amendments I’m making, none of which are a contractor’s dream job, although all useful for maintaining the integrity of the building. I’ll start with the three that are mostly labour:
1. Adjust insultation. Remove mouse dung infested fiberglass. Eew. Removing the mouse contamination needs no explanation. The insulation does.
The north wall has a stud frame and was insulated from floor to ceiling with pink fiberglass. Insulating the interior of the basement to floor level is a no-no, unless the foundation is insulated on the outside. This is because it alters the frost line, which can stress the footings and foundation of the house1. However, to avoid heat loss, it is a good thing to insulate the basement above ground level. I removed the insulation below ground, leaving the above ground material and covered it with drywall. (The photo shows the result after painting (more about that below)).
For insulation removal, I wore safety googles, an N95 mask, rubber gloves, long pants, and a hoodie pulled tight over my hair. I must have looked pretty psycho but hoped no one saw me as I was in the basement. The old insulation was bundled in garbage bags and taken immediately to the local waste facility that processes such materials.
I also replace the mouse soiled fibreglass in the basement header, between the joists, with clean Roxel. This is recommended to increase basement insulation. (This photo shows ‘after’ walls.)
2. Repair and repaint concrete floor. This situation is one of a classic era-after-era modification that lead a mess I am dealing with in 2022. It’s reasonable to assume, based on the age of the house, the basement started with a dirt floor. As time when by, stuff happened. Fast forward to now, and I have a deteriorating, painted concrete floor.
My analysis is that there has been moisture under or within the floor, and the original mix of cement was not the greatest quality.
Invasion of moisture from the outside has been addressed as well as possible with external grading and drainage.
In some sections of the floor, the paint scraped up easily, revealing a layer of sandy dirt beneath. Dampness between the floor and paint have likely deteriorated the concrete surface. A bit of work with a paint scraper and wire brush got to a stable surface. Where there is more than a few millimeters depth missing, or rocks that popped out, I filled the area with cement2.
Interestingly, the concrete that was never painted (e.g. under applicances) seems to be in better shape than the painted stuff. The moral of that story is, only use the correct products, designed to seal concrete, for a basement floor.
In another area, the pebbles in the cement are larger than ideal (some as big as 2″ across), and the ratio of stones to cement too high. It could also be that the floor was at one time gravel and then cement was poured over it, which subsequently disintegrated. There was newsprint between the paint and stones in one spot. This area is very lumpy and uneven. I can’t think of a good reason why anyone would install such a floor, other than poor quality work or planning so perhaps the explanation is deterioration covered up with paint.
Unlike many other areas of the floor, the paint was stuck to this bumpy surface, so chemical paint stripper was required to get to a surface where cement could be added to flatten out the surface. A grinder to remove the paint wasn’t an option due to the unevennesss of the floor. If it was outside, a power washer might have worked but this seemed way too messy for indoors. And a bucket of paint stripper is $15, a pressure washer at least 10x that.
Getting a smooth, slopping (because the floor needs to slope towards the drain, which is a fair bit lower and about 6 feet away) surface was harder than anticipated. I’ve done concrete patch before, but not on this scale. Several sessions later3, the floor was acceptable for an unfinished basement and ready for paint (after curing4).
In many locations, there were small (1 to 2 cm) pits of deterioration. When probed, these disintegrated into sandy powder, leaving a well-defined hole, the size and shape of a pebble. My guess is that there were lumps of sand or dirt in the aggregate, or the cement had sand added and was poorly mixed. This has lead to localized instability. No worries – after digging out, easily filled with a bit of new cement.
The fun part was painting the repaired floor. Sort of like icing a cake. I even added sprinkles, or multicoloured flecks that dissolve into wet paint. Great for adding interest to the floor and distracting from the less than even surface of an old concrete floor.
3. Stablize foundation wall surface and make them look nice.
Like the concrete floors, the foundation walls show a bit of weakness in the cement mixture and perhaps installation. There is much honeycombing and spalling of the concrete. The walls were also covered in dirt, so it was hard to distinguish where the dirt stopped and the spalling started.
I took a scrub brush to each wall, dislodging as many poorly embedded pebbles and lose material as possible. Then I took my adhesive cement and pressed it into the roughests areas, with the goal of stabilizing the surface and preventing aggregate from dropping. In an unfinished basement, rough concrete is fine, so the patching didn’t need to be ultra smooth.
The satisfying part was putting the paint on the walls. By accident5, I found a shade like clean, new concrete. I embraced the uneven surface of the wall, letting the existing concrete fleck through, for a two-toned, textured effect. Accenting with white and pink streaks and splashes made the walls look fresh and bright. This was creative, didn’t take very long, and made for a satisfying finale to the basement remediation project. (This picture shows the painted wall and unpainted floor pictured above after the gravel had been cemented over.)
It was a long, messy, scrubbing on hands and knees job, but the results look pretty good for an old unfinished basement. Time will tell how effective the resurfacing and painting was for stabilizing the cement.
1 In cold regions, basements prevent the soil outside the house from heaving or cracking the foundation by keeping the soil from freezing. Basements left unheated, or those insulated on the inside right down to the basement floor level, counter this effect. Both lead to potential of the soil around the basement freezing in cold weather, possibly adhering to the foundation walls outside and pulling on these walls in an uneven way.
2 I use ‘Top and Bond‘. It’s designed for repairing concrete and has a polymer adhesive in it to make a good connection with the existing concrete. Hydraulic cement also works fine, as it is designed to fill gaps and plug holes.
3 YouTube videos convinced me to go for dumping lots of cement at once and trowelling it out quickly. My instinct was to do small areas at a time but this was harder to blend into a uniform 8′ x 4′ section. Also, to feather the edges, I go over the freshly layed cement with a wet paint brush. Once it’s dry, I use a scraper to pull off the grainy bits which ends up being a lot like sanding drywall filler. This makes a reasonable interface between the old floor and new patch.
4 Depending on the source your read, freshly poured concrete should cure for 30 days before painting. Not sure if the amount of repair I did qualifies as freshly poured concrete, but there’s plenty else to do, so I’ll wait the 30 days.
5 In the mis-mixed, deeply discounted area of the local high end paint store. I wasn’t all that fussy about what colour the basement wall were, so getting a deal worked out great.