Mat Foundation Reinforcement Spacing
Mat Foundation Reinforcement Spacing
(OP)
Hey all,
Before I get started I am just going to say that this post is not an attempt to open the 0.0018bh vs 4/3As reqd vs 200/fy debates that have been posted before.![[tongue] tongue](https://www.tipmaster.com/images/tongue.gif)
By analysis, I need 0.0018(12in)(18in)=0.39in^2/ft for reinforcing both faces of an 18" mat foundation. That works out to be #7 bars at 18" o.c. which meets the requirements of ACI 318-08. My question is, would it be better practice to use the #7 bars at 18" o.c., or use #6 bars at 12" o.c. which would increase the qty of steel reinforcing by about 10%?
Just curious what others feel is a better method to use. I have several of these footings and a 10% savings in steel might be worth it, but not at the expense of structural integrity.
Before I get started I am just going to say that this post is not an attempt to open the 0.0018bh vs 4/3As reqd vs 200/fy debates that have been posted before.
![[tongue] tongue](https://www.tipmaster.com/images/tongue.gif)
By analysis, I need 0.0018(12in)(18in)=0.39in^2/ft for reinforcing both faces of an 18" mat foundation. That works out to be #7 bars at 18" o.c. which meets the requirements of ACI 318-08. My question is, would it be better practice to use the #7 bars at 18" o.c., or use #6 bars at 12" o.c. which would increase the qty of steel reinforcing by about 10%?
Just curious what others feel is a better method to use. I have several of these footings and a 10% savings in steel might be worth it, but not at the expense of structural integrity.






RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
Also...glad you use the correct amount in the mat (i.e. 0.0018 on each face) assuming you have moment in both + and - directions on the mat.
RE: Mat Foundation Reinforcement Spacing
We typically restrict spacing to 12" or less, especially for top reinforcing in mat foundations. In most cases, the mat (soil supported or pile supported) also served as the top of the cellar / basement and was not buried in the ground.Therefore, we use smaller bar sizes and restrict the spacing of the top reinforcing from crack point of view. Also with a rebar spacing at 12" or less, it makes walking over the rebar-mat a bit easier during inspections and concrete placement.
RE: Mat Foundation Reinforcement Spacing
Dik
RE: Mat Foundation Reinforcement Spacing
Dik
RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
More good information can be found in the Concrete International article http
It's no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don't know which half - LORD KELVIN
RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
It's no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don't know which half - LORD KELVIN
RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
Also, the WWR placed in the article refers to a dual layer of top reinforcing, which could hold the WRR in place. With only a single layer, the WWR will be wavy and could effect cover.
RE: Mat Foundation Reinforcement Spacing
RE: Mat Foundation Reinforcement Spacing
#7. and ofcourse it will be easier to walk.
Thank you.
RE: Mat Foundation Reinforcement Spacing