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Method to tell cinder block from concrete block??

Motorapido Member Posts: 224
I'm inspecting a property for possible purchase that was built in 1950. A simple little 900 square foot two-story cottage deep in the woods, built with block walls on a concrete slab. Block walls run continuously from slab to roof. Block is not covered with siding on the outside and it is uncovered on the inside, with the block painted on the inside and outside faces. No inside furring/framing/drywall -- just the block wall on the interior. I hear horror stories of cinder blocks failing and causing expensive repairs, compared to the longer-lived concrete block. Is there a method to tell visually or through any other method whether these blocks are cinder block or concrete? No pics right now. But I'll be inspecting the property tomorrow and can take pics if it is possible to tell from a pic.


    EBEBRATT-Ed Member Posts: 8,540
    Only by the color as far as I know. Cement blocks look like......concrete lite gray. Cinder blocks are dark grey at least around here.

    If they are 1950 I would bet cinder blocks, but I never herd of them failing.
  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    There's also a difference in feel and texture, but unless one is rather familiar with both it can be hard to tell.

    As far as failing goes, it's only a problem -- so far as I know -- if they are overloaded or stressed in ways they aren't meant to be. They won't take as much compression as a true concrete block, nor will they take tension. Thus a tall wall could be a problem, or one that supported a heavy floor. Also perhaps not the best choice for a retaining wall. That said, the structure you are describing shouldn't present an overload on them. Any distress in the block should also be readily evident in the form of cracking -- sometimes through the block, and sometimes through the mortar.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pecmsg
    pecmsg Member Posts: 1,892
    Both will fail if or when water penetrates and the freeze thaw cycles begin. Without moisture long life.

    A hammer, Cinder blocks will sound hollow.
  • Youngplumber
    Youngplumber Member Posts: 500
    I see them fail all of the time here in Iowa. Mostly all of them here are failing due to lateral pressure though. Likley related to improper footing drainage. Keep in mind I'm talking basements here or walls built underground. I don't know why anyone would use block for a basement but they did.

    I think your fine either way if the wall is all above ground or close to it. 
  • STEVEusaPA
    STEVEusaPA Member Posts: 4,823
    How do they look after 70 years?
  • Motorapido
    Motorapido Member Posts: 224

    How do they look after 70 years?

    I'll find out when I inspect the property tomorrow. The only thing I don't like about this property so far is that it has no steam boiler (heated with a wall-hung natural gas heater). But heck, it's just a tiny cottage deep in the woods. I can enjoy my steam boiler at home.
  • hot_rod
    hot_rod Member Posts: 14,552
    Any signs of water leakage inside the blocks? That may indicate the site drainage is not adequate, which seems to be the root of many foundation issues.

    Workmanship also, around here a lot of farm buildings were built with "farmers concrete" basically they throw a lot of rocks in the mix to "extend' it. You end up with a very weak pour.

    As the youngster mentioned :), hydrostatic pressure or freeze thaw in or around the block would be a problem.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jamie Hall
    Jamie Hall Member Posts: 15,373
    Neither cinder block nor concrete block are well suited by themselves to retaining walls, as I mentioned above -- and that applies to foundations with one side open to a basement below grade as well -- unless the outside is built with fabric and free draining coarse stone down to the bottom of the footing. They can be used, but they must have reinforcing steel tied into the footing -- which must be concrete -- and then filled with concrete. Cinder block is a little worse than concrete block, but both will fail unless that's done. (Concrete block will fail in the mortar, cinder block will fail in either the mortar or the block).

    Above grade they both will take vertical loads of reasonable values, but again, unless they are reinforced, they will not take lateral loads (as an overlooked example -- a flat or nearly flat roof is OK, but a pitched roof is not, unless the ends of the rafters are tied independent of the wall; a shed roof can be very problematic).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,252
    Cottage deep in the woods with natural gas? 

    Must be propane. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
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