Residential Basement Wall Reinforcing 4

[jandlo]

I have a contractor suggesting my basement wall reinforcing is excessive. I'm sure it is in terms of strength but for temp and shrinkage crack control and meeting code I'm not so sure. It's a 12" thick wall (mainly for a 2x6 wall with a brick veneer. It's 11'-0" from top of wall to top of basement slab and retaining a maximum of 8 feet of soil. I"m showing 2 layers of #4 bars @ 18" OC each way. The contractor wants to use a single layer of an unspecified bar size @ 24" OC each way.

My concern is controlling cracks over time and the threat of water infiltration.

Correct me if I'm wrong but because the wall is greater than 10', the prescriptive design in IRC is not applicable which means that the max 18" OC spacing from ACI applies.

I also wonder about the ACI provision about walls 10" thick and greater requiring 2 layers of reinforcing (except basement walls). Why the exception for basement walls. And is it reasonable to use 2 layers in my case -- a residential basement wall 12" thick?

 

[HouseBoy]

If you can analyze the wall and reasonably determine the bending stresses, then you should be able to prescribe the reinforcement needed. Sometimes in residential basement walls the bending is not always in the inside face (for example there can be negative bending at a corner when the wall is spanning horizontally).

Regarding the 18" max spacing requirement - One thing I have done is to when using 24" bar spacing, take 24" tributary area of load and resist it with a design section of only 18". Doesn't seem like a tremendous savings (and I don't do that often) but it might be a reasonable way to justify some wider spacing.

Like you, I like two layers of rebar for crack control also.