Poured Concrete vs. Block Walls

45 responses

  1. Marianna Giovannini
    April 10, 2012

    If your foundation has the drain piping system on the perimeter, does it still need the outside of the wall coated with a tar mixture?

    • Tim Carter
      May 23, 2012


  2. Ben
    May 27, 2012

    You always want exterior water proofing, even if interior drainage is good, because any water will bring mold, algea and in cold climates, frost and cracking.

  3. Curtis Sheldon
    August 5, 2012

    Is it common for the sand to migrate out of a pored foundation wall? In one area, I have a light tan "dust" on the wall (top to bottom). I vacuum / brush it off and it re-appears.

    • Tim Carter
      January 11, 2013

      Curtis, you need to schedule a 15-Minute call with me.

  4. sallee carrigan
    February 27, 2014

    Is a stick house on a concrete ribbon foundation asking for trouble?

    • Tim Carter
      February 27, 2014

      Not if it's all built the way I would do it!

  5. Mary
    August 3, 2014

    I am moving a house in on a lot. This is Texas and the lot is sandy. What kind of foundation is recommended?

    • Tim Carter
      August 3, 2014

      One with reinforcing steel.

  6. Matt Roth
    August 22, 2014

    I was recently looking to buy a house with a block built foundation/ basement. It appears that someone has installed some sort of piller supports on all walls except one. The wall that has none is a little bowed, and has a nice sized angled crack that leaks water. I just witnessed the sump pump running you could hear the water going out of the house overhead and 3 minutes later the water would literally pour back in the crack! Besides getting the water away from the house how could you fix this?

  7. John Schipani
    August 28, 2014

    On a poured concrete or block wall, when furring strips are used to attach drywall, How do you obtain the depth to install electrical boxes? We. Are building a home in southwest florida.

    • Tim Carter
      August 29, 2014

      Chip out the masonry or attach 2x material.

  8. julie
    September 6, 2014

    Hello, I want to buy a house that has block foundation. The house has a plastic that covers the blocks and you can see white pots on the block. What is your advise?

    • Tim Carter
      September 7, 2014

      My advice is to read all my past columns on efflorescence.

  9. Terral
    September 17, 2014

    Looking to add 120sf to on grade garage foundation. What is the best way to connect footer slab to existing foundation?

    • Tim Carter
      September 18, 2014

      Pin the new footer to the existing with 5/8-inch rods that penetrate into the old at least 6 inches.

  10. Dave Butler
    September 18, 2014

    I have a seasonal home built with concrete block foundation on sandy soil. Last time I was there I noticed on one corner of the wall the blocks had filled with water, about 25 of them. I did not have the time to empty them out.
    Do you think the water entered from the outside water line or from under the cove joint and worked its way up.
    I guess they had about 9 inches of rain the week before.
    Furthermore I noted a horizontal crack in the front facing wall but I did not detect any bowing in that wall

    • Tim Carter
      September 18, 2014

      The water seeps through the mortar joints - usually the vertical ones. You NEED my Linear French Drain DVD!!!! If you install one as I show in the DVD, you'll NEVER have water in the block again.

      • Dave Butler
        November 1, 2014

        whats your take on my comment about the horizontal crack ?

  11. Brandon
    November 11, 2014

    I'm going to replace one of the block walls in my basement thanksgiving weekend. All four walls are bowed in and they are bad at the cornets too. How do you tie in a new straight wall to a bowed at the corner? Lots of mortor?

    • Tim Carter
      November 12, 2014

      You cut the block to fit.

  12. Spencer
    January 4, 2015

    I want to build a tornado shelter because I live in tornado alley. There are lot size construction so it has to be aboveground essentially. I'm concerned that CMU blocks or just strong as a poured wall, even if I backfill it and reinforce it with rebar. I am using FEMA's drawings.there will be a solid poured top and a solid poured foundation with the rebar tight end at least every 16 inches on center. Am I mistaken that it won't be as strong as a solid wall?

    • Tim Carter
      January 8, 2015

      The block MUST be filled with pea-gravel concrete. Hollow block can be EASILY penetrated with a flying 2x4. Then, imagine a car or pickup truck flying through the air that RAMS your shelter!

  13. Jeremy
    January 10, 2015

    I want to build a 30x60 single story building with a 12 ft ceiling and a pitched roof. I live southern Indiana. And the building site will most likely be in a cleared out space in a wooded lot. Not terribly sloped but not exactly level either. What sort of foundation would you recommend?

    • Tim Carter
      January 11, 2015

      Poured concrete.

      • Jeremy
        January 12, 2015

        Thank you! How thick a poured concrete foundation?

  14. David
    January 16, 2015

    I'm looking at purchasing a house with a stone foundation/basement in the Midwest (Kansas City). I would like to add a two car garage with a suspended floor with space underneath that could be finished and connected to the existing basement. Can this be done?

    • Tim Carter
      January 16, 2015

      Yes, it can be done.

  15. Bob
    February 9, 2015

    I live in the Kansas City area. I have a basement that is referred to as a Michigan basement. The basement is rectangular with a 7' ceiling. Half of the basement wall is a full 7' tall. The other half has been dug out, leaving a 2' knee wall on a 5' tall dirt ledge. A poorly formed sister wall was put in some time in the past to hold the dirt ledge in place. that sister wall was not reinforced and is starting to fail.

    My question is:

    Is there anyway to fix this wall? Replacing the wall exceeds the value of the house. Many engineers have told me that the sister wall is not load bearing and therefore does not need a footing under it. I have been monitoring the sister wall and it has not sunk any in 10 years, but it is bulging in to the basement. the result is the knee wall is starting to sink.

    Is it possible to hand-stack concrete and fix this wall?

    • Tim Carter
      February 11, 2015

      Yes, the wall can be fixed. We can discuss options on the phone if you want. It's far too detailed to do in comments here.

  16. Noel
    March 24, 2015

    My builder is installing foundation blocks 6x8x16. He places the steel from the base of the trench within the core of the blocks. But as he lay more blocks and the foundation gets higher the steel is no longer visible. Was this done right?
    It's like 4 rows height of foundation blocks. He argues that bringing up the steel is not necessary because of the height. Please help.

  17. Mat
    May 17, 2015

    Hi, I'm renting a house that I also have the option to purchase in 5 months in Winnipeg Manitoba Canada. It has a block foundation and a fully finished basement so it's hard to tell the shape of the foundation. The reason why I suspect there to be a foundation problem is throughout the house (only on main floor not second story) there are cracks in the walls almost around every door frame . I was told that's signs of stress and I could be looking at foundation problems . The furnice room is the only room in the basement that isnt finished and there is a small horizontal crack right across the middle of the walls , the crack isn't big, can't fit a dime in it. Also underneath the stair case is another little closet with bare foundation showing and I looked and there is a large crack that seems to have some sort of filler in it but the filler is loose I can wiggle it with my finger.

    Please tell me your thoughts on this and if you think I'll be looking at some hefty repairs on the foundation in the near future if I choose to purchase this property.

    Thanks !

    • Tim Carter
      May 17, 2015

      It's really hard for me to speculate without being there, but based on your description, I'd NEVER buy this house. READ all my columns here in my Structural category. Just type that word into my search engine to get to it. I have a column about the EXACT cracks you see at each doorway!

  18. Scott Hartman
    June 19, 2015

    I recently had a soil engineer out on a piece of vacant land in which will require a mound type septic system. Everything is a go for that. I do however have one concern we talked about. The land has some very shallow areas toward the back in which he called shale rock. My concern is building a forever home with a basement as well as having a backyard for the kids to play in and not a swamp. Is there things that can be done to drain/remove some of this excess water that sits back there. Any expert advise would be appreciated. Thank you so much. Also want to keep a dry basement. Have a great day.

  19. Stan Brown
    August 2, 2015

    Tim, no question, just wanted to thank you for all your info. I have been debatting on which way to build (block vs poured) I live in a house with a block basement now that I did not build and it was not build corretly and it has been nothing but trouble. (Water, cracks, mold, etc. I'm selling and starting over. I am looking to start building a house with a full basement and the info you have supplied is a great help.

  20. Rob
    September 2, 2015

    I have a question I live in the Philippines, i would like to build a basement, I was told every 2-3 years the area I live in if the drainage is clogged then I might get about 2ft of water outside. Now I could raise my house but I was wondering if I went along with building the basement, had an outer and inside wall 1ft apart and then poured concrete in the middle and then treated the outer wall with a concrete sealer, would that be ok? Maybe I'm over thinking it I'm not sure. I would just hate to build a basement and then have to worry about it flooding. I did intend to put a sump in the room as well. Your advice would be appreciated.

  21. John the Fig King
    October 21, 2015

    Hi, I just constructed a small "wall" 18" high x 32" long x 8" thick to support 4 x 4 8ft posts for a lean-to roof over an existing basement door. It extends down 12" below adjacent grade. It is formed with wood boards. How soon can the form be removed? I know that the concrete needs light wetting while curing. The roof is eager to be built.

  22. Gary Jenkins
    January 29, 2016

    Gary Jenkins

    We are having a concrete retaining wall for a fence footing built by a sub-contractor of the Fencing company. The contractor is preparing to pour concrete. My concern is that per my request the metal fence posts were seated in PVC and then concreted. Because there has been delay due to weather (rain) there is now dirt that has built up over the concrete seating for the posts. I'm questioning if there is a concern over pouring the concrete over the dirt (which will cause a layering effect of concrete/dirt/concrete). It's my thinking that if the dirt then washes out (from natural drainage) between the layers that there will then be space and will the weight of the fence then lead to cracking in the will. The subcontractor says no, but since he has been less than knowledgeable up to this point, I'm reluctant to trust him. Your thoughts would certainly be appreciated!

  23. Janet
    April 16, 2016

    We have a walk out basement. The earth around it is clay. The basement is 12 inch block. My husband is good about keeping gutters and downspouts clear and directing water away from the house. The basement wall is 9 or 10 feet tall. We recently noticed, after living there eight years (house is 12 years old) that the wall into the hill leans forward one inch at the top. We removed the Sheetrock to see if the wall had damage. It is perfect, no cracks, very dry. One structural engineer told us the wall had moved and was compromised. Should we get a second opinion? The whole basement is tiled. Not one cracked groutlines, no cracks, not even hairline, in Sheetrock, glass shower doors close perfectly, doors and windows close perfectly. The interior walls lean by same amount, but doors are square. We think the wall always leaned, was constructed that way. Decks are flush, concrete patio is not cracked and is flush, stacked stone on exterior is perfect. We also believe the previous home owner, who finished the basement himself, came off the back wall. In our minds, if the walls were pushed, things would not just be slightly tilted in but also off square. Look forward to your opinion on our second opinion. Also, if we do brace the wall, what would you recommend? He recommended steel h beams from footing to floor joists. Upper level is log.

  24. vikash
    July 4, 2016

    We are planning to raise the Ground Floor by 10Ft height and construct G+2 Floors. i.e ground floor + 2 additional floors.
    Can we have the Large rock based foundatation for this 10Ft wall on all 4 side or just concrete with Steel road + bricks for 10Ft.
    Pl. suggest for cheap and best solution

  25. Martin Land
    September 5, 2016

    I have a question that I've been unable to find an answer for; but then, it may just be a stupid question.

    I'm thinking of building a shed, with a "basement"
    I've researched all what I think I need to understand how to do the concrete floor and I want to use cement blocks for the walls, with rebar reinforcement.
    I would then build supports to pour the "basement ceiling/shed floor" on top of.

    My question is this:
    After having the basement hole excavated, I'm going to end up with a large amount of dirt.
    What would happen if I used this dirt, to fill in the gaps in the concrete block?
    I could do it two ways.
    One is to fill it in as each layer is cemented in place and tamp it down solid.
    The other way is to wait until the walls are finished and then fill them in, tamping them down by building 2 different kind of tampers.
    One made with a solid bottom for the holes with no rebar and one build with a hole in the middle for the ones with rebar.

    Please don't laugh to loudly.

  26. Jared Nanke
    September 21, 2016

    We're a fourth generation family owned and operated design-build firm with nearly 70 years experience in building homes. Our background is in masonry and we've been doing block foundations going back to my great grand father. It wasn't until recently, some prospective clients brought to our attention concerns of block foundations that we discovered articles saying block foundations are hollow and not reinforced with steel. Since the age of 4 years old, walking around the job sites with my father and uncle, it was common knowledge to me that block foundations were reinforced with vertical and horizontal steel and filled with concrete. Reading up online and finding where builders are not doing this just blew all of our minds. Prior to reading online, we were really struggling to understand these clients admit concerns of block foundations. Now I see where they're coming from. Thank you for the article!

  27. Rich Wilson
    October 24, 2016

    I'm in the desert with 6' tall block fences around my whole property. The fences have stucco applied on the outside, looking away from my yard. My property is 38 inches above the grade of the surrounding area and four rows of the fence block retain dirt. The ground pitches rapidly down just outside my fence. When it rains, water soaks the soil and eventually loosens the stucco on the outside. I'm tired of paying to have it replaced every 5 years. What can I do to eliminate this problem.

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