I live in an old house (somewhere between 1870 and 1920) with a retrofit basement.

I also have a high water table, so during the spring rains, we get a trickle of water in the basement ( we've come to accept it as part of the personality of the house and just make sure nothing is on the floor.)

The floor is poured concrete, but whoever did it left high spots and low spots, and of course one of the high spots is between the biggest low spot and the drain.

So my question is:

Short of taking out the entire floor, is there something I can do to level out the low spots? Or can I cut/grind/chip a groove deep enough in the high spots to act as a channel?

  • Aside from the highs and lows is there sloped pitch down to the drain ?
    – Alaska Man
    Apr 2 '20 at 19:01

Too long for a comment: I like to reduce high spots because I have found with moisture most self leveling compounds just don’t last , a 4” angle grinder is a handy home tool and can be used to cut a trench or with painstaking work grind it all down, inexpensive grinders start at ~30$ and pro versions can be close to 200 for a 4” , going up to a 9”angle grinder with a carbide surfacing blade/ bit will cost around 300 but can do a large amount in a short time this tool is used to cut the high spots down faster than masonry disks without dust. I use water so a GFCI protected receptacle or extension cord is a must with my setup if no water is used the blade or bit doesn’t last long this eliminates the need for a dust mask but a shop vac and a large rubber floor squeegee is helpful.

  • Wet is good. I would add that grinding DRY concrete will create an EXTREME amount of dust that will permeate your entire house if you do not seal off the work area very very well. A respirator is needed, not a mask. A fan in a window will help evacuate the dust, it is very fine and will stay airborne for a long time.
    – Alaska Man
    Apr 2 '20 at 19:12
  • There's a dust shroud that surrounds a 9" grinder that connects to your shop vac. I highly recommend it, as it massively reduces the amount of dust emitted. I also recommend taping or removing CO2 sensors and smoke alarms, as the dust can destroy them. There's also a diamond cup blade that works quite well.
    – gbronner
    Apr 2 '20 at 19:44
  • Tagging on Alaska Man, concrete dust can also contain crystalline silica which is not good for the lungs. More information at these two links 1 nj.gov/health/workplacehealthandsafety/documents/… 2 cdc.gov/niosh/topics/silica/grinders.html
    – Ack
    Apr 2 '20 at 21:04
  • 1
    I agree with dust being bad and making a mess this is why I use water and a grinding wheel I think it has carbide blocks , and can use a dust collector but even with a water bath trap there is some dust with water on the surface there is no dust when done with a wet surface.
    – Ed Beal
    Apr 2 '20 at 21:37

This is commonly done and is done so using self-leveling concrete or cementitious products. These can be found at your local home improvement center. The basic idea is that water, as a liquid, will always be level and the leveling compounds are very thin and act like water to become flat as you pour and spread it over the unlevel surface. Then they harden to a very hard surface.

  • With self leveling concrete How does the OP maintain a sloped pitch to the drain ? ( if there is one ) By its nature it will self level.
    – Alaska Man
    Apr 2 '20 at 19:05
  • I would form around the drain area using any convenient means, then later I'd use a vinyl patch compound to taper the ledge down to the drain.
    – isherwood
    Apr 2 '20 at 19:51
  • I wouldn't call the finished product a "very hard surface", though. It tends to be chalky and shouldn't be subjected to long-term foot traffic. It could be covered with self-adhesive vinyl tiles, for example, or floor paint.
    – isherwood
    Apr 2 '20 at 19:53
  • I missed that they had a drain when scanning too fast, and also that they do not seem to be after a level working floor but just a drainage solution. In that case, isherwood's solution is the correct one
    – Ack
    Apr 2 '20 at 20:57

If your primary goal it to drain the water, then simply cutting a slot through the high spot can be quite effective.

Even though they are quite small (and as such will need cleaning somewhat more often than larger ones would) even an 1/8" wide cut made with a dry diamond blade will move water through a high spot (I've done that) to a sump/drain, and greatly reduce ponding/puddling in the basement. In my case I had a grinder, got a dry diamond blade for a tile job, and used it on the basement floor later.

If renting a tool for the job, a diamond bladed wet saw (preferably with a somewhat wider kerf) would be a better choice - but adding water to electrical tools not designed to have water spraying around is chancy at best, so I chose a dry type blade when purchasing one for my existing tool. Dust control is important for both your own health and the survival of your tool - it's best to have someone else holding a shop vacuum nozzle sucking up most of the dust before it can go anywhere, or lacking a helper, to attach the shop vacuum hose to your chosen tool somehow.

Aside comment - I found that painting the concrete also helped immensely with water movement/drainage - when the surface of the concrete is not acting like a sponge, the water is much more prone to just follow the drainage channels and leave. I chose white paint and the basement felt 3 times brighter as a result, too.

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