The maximum length of basement wall placed in rigid foundation?


As a continuous external restraint, the basement wall should have a reasonable length for concreting to control crack due to the temperature drop and shrinkage. What is the method for estimating the proper length without using reinforcement?



7 thoughts on “The maximum length of basement wall placed in rigid foundation?

  1. wyfjta says:

    About this matter, we used the contraction joints for preventing the cracks.
    "The upper portion of the wall is likely to cool and shrink faster than the lower part of the wall, that is also more restrained. Both conditions allow additional tensile stress within the concrete that will likely cause some cracking" (ACI 224. 3R – 95).
    The distance between 2 contraction joints is about 6m.

  2. Eagle says:

    But I can see reinforcement bars. Have you inserted a re-injectable hose inside the wall before casting? I think these cracks are early thermal cracks as they appeared just after striking the formworks. To calculate if these cracks are caused by that, use this spreadsheet and let's discuss: http://attchd.in/kCcLT

  3. wyfjta says:

    Thank you for your share.

    In my case, the basement wall 900 mm thickness and ~ 1.1 m height for one pour. The crack initiate at the top of the wall and both sides.

    You can see the detail in the attachment.

  4. Eagle says:

    My case described above is for the reinforced concrete structures such as culverts, underground parking structures, etc.

    I'll be sending you my hand notes for this case.

  5. Eagle says:

    Well, I've just checked Table 6.3.1 and sounds new to me as we normally reinforce basement / retaining walls. Is the wall in your case too thick? What is the height of this wall? Interesting and gonna read more an out it.

  6. wyfjta says:

    The scanning files of your hand notes is so helpful for me. Thanks so much for your share.

    My truely concern about the maximum length of contraction joint spacing for this case. ACI 207.2R give a application for calculating the effect of temperature drop & shrinkage for continuous external restraint such as basement wall placed in rigid foundation. Table 6.3.1 page 20 give a design temperature limits for unreinforced concrete walls (for limiting cracks to 0.009 in.) corresponding to contraction joint spacing.

    When continuous external restraint is dominant, the crack will initiate at the base or restrained
    edge where the restraint is greatest and progress upward or outward until a point is reached where the stress is insufficient to continue the crack. This can be reduced by using reinforcement.

    But in some case, the cracks will occur initially at the top of the wall, not at the base? And this crack may be due to drying shrinkage, not due to external restraint?

  7. Eagle says:

    For the underground structures like basement retaining walls, I haven't seen any restrictions on the length of any structure due to temperature control. This applies only to the over ground structures which is found to be between 40 ~ 60 m. Some say 50 ~ 80 m, however I prefer to carry out some thermal analysis for any over ground structure that exceeds 60 m. If interested, let me know to scan and send you some hand notes in this regards.

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