CMU Pier

Discussion in 'Framing and Foundation' started by matty, Dec 26, 2017.

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  1. Dec 26, 2017 #1

    matty

    matty

    matty

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    Good Morning! First post here. I did a search and didn't find anything. I am getting ready to embark on the main living space renovation. I had the engineer out and sized the beam for me and give me the details. I have 1 question in which the engineer hasn't responded, so I wanted to ask you all.

    In the specs it calls for a fully grouted CMU piers to be built, 2, to go at the end of the beam. I understand all aspects of this except the pier itself. It states a "fully grouted cmu pier"

    For this do I need to pour a 4" concrete slab first? There is no specification for this. Also, with fully grouted, does this just mean the grout between the concrete blocks, or do I need to fill the blocks also with cement and rebar? Just need some clarification on this. Beams are ordered and delivered, and working to get ready to start building the temp walls but want to get the CMU's built.
     
  2. Dec 26, 2017 #2

    mudmixer

    mudmixer

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    You should excavate to get down to strong bearing soil and at least to the local frost depth If is on an exterior wall. - It must not be a very long beam span if no center pier was specified.

    Will the addition have a crawl space or basement?

    A fully grout grouted pier is usually 16"x16" unless it is a part of a foundation wall. If it specified to be "fully grouted", you would used 2 - 8x8x16 blocks and alternate the orientation every course(layer). If it is not specified as reinforced, 4 #3 rebars in each pier would be cheap insurance. It is best to fill the cores of the block with grout and not mortar that is much more fluid and will fill the block more completely with grout that has some 3/8" to 1/2" rock in it. In masonry, the strength of the mortar is not a major strength factor and the strength of the block controls. The mortar is just the allow the you maintain a plumb and level pier.

    You could save a few pennies by going to smaller block, but then the block orientation for each layer would pose some problems.

    Dick
     
  3. Dec 26, 2017 #3

    joecaption

    joecaption

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    Why not use solid block and skip the having to fill them part?
    No one here has seen the plans, even know exactly what it is your doing, no location in your profile, or what your soil conditions are so it's hard to say exactly what needs to be done.
    I've added at least 85 piers under 100 plus year old homes and one time a church where the HVAC company had cut a 12 X 12 main beam in half to run the A/C lines in VA.
    All the ones we did had 24 X 24 X 8" thick footings with 1/2" rebar in the middle of the footing. (no way is 4" thick going to be enough)
     
  4. Dec 26, 2017 #4

    JoeD

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    Fully grouted means the cores of the blocks are filled solid.
     
    Steve123 likes this.
  5. Jan 15, 2018 #5

    matty

    matty

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    The wall I am removing is in the center of my house, between the living room and dining room. I have put below in blue the information from the engineer. I am located in Macon, GA. The home has a block foundation on the outside perimeter and then piers space under the house that the floor beams sit on. I am having to build two new piers for this beam I will be installing, I will have the posts then block from the floor under those posts to the pier. I was hoping when I first started the project I would have piers where I needed them, but I don't so I am building new ones. Just want to make sure I get it right. I have a home designer coming in to help me with the new layout, because for some reason I just can't get a clear vision in this house (normally I can, but sometimes professional help is needed). So from what it seems I will have to do fully grouted, meaning filled piers, this will be slightly more difficult since I am working under an existing house, but not impossible, and I am up for the challenge.



    "The LVL has been sized to span a maximum of 20'-0". The LVL tributary area is 16'-6" (half the distance from the front wall to the back wall of the home). The assumed loads are as follows (Note that PSF stands for pounds per square foot. PLF stands for pounds per linear foot):
    • Existing ceiling framing consisting of 2x6 joists at 16" on center with a plywood attic floor, fiberglass insulation, and 1/2" drywall ceiling below for a total of 11 PSF.
    • Existing roof loads (15 PSF roof dead load and 20 PSF roof live load) transmitted through diagonal braces that are to be reinstalled on top face of LVL.
    • Attic live load of 20 PSF for uninhabitable attic space with storage.

    The LVL size is a three ply 16" deep Paralam PSL 2.0E having a minimum bending strength of 2900 psi (this bending strength is typical for a Paralam PSL 2.0E LVL).

    The LVL is assumed to be installed with the bottom face flush with the bottom of the existing ceiling joists. Install one Simpson LUS26 joist hanger at every existing ceiling joist. The joist hangers are to be nailed to the face of the new LVL. Support each end of the new LVL on a built up wood column constructed using a four ply 2x6. The plies of the built up wood columns are to be connected using two rows of 16d nails at 6" on center. Stagger the nails in adjacent rows. Nail the built up wood columns from both sides (perpendicular to the wide face of the 2x6). Provide solid 2x6 blocking in line with the new built up wood columns below the existing floor level. The solid blocking is to bear on either the existng CMU piers or a new 16"x16" fully grouted CMU pier. "
     
  6. Jan 15, 2018 #6

    bud16415

    bud16415

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    That’s pretty common down south all those piers cut down on the span and thus the timber size. depending on the head room to work down there it might be slow going. Getting the footing dug and poured will be the hardest part I think. I have only watched them build these pier homes and never done it but I even see them laying up the piers out of bricks and brick size cement bricks. I guess that eliminates pouring and filling block in cramped quarters.

    Post some pic when you get to it.
     
  7. Jan 15, 2018 #7

    matty

    matty

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    My other question would be, could I use solid cement blocks and grout between, to then not have to pour grout down the holes of the blocks? Fortunately I have about 4.75 feet between the ground and floor joists, and I am only 5'6 so it is good for me working under the house, not really comfortable, but definitely doable.
     
  8. Jan 15, 2018 #8

    bud16415

    bud16415

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    Only thing I can see is if the report calls for rebar in the cores and filled. Solid blocks are no fun to move around but if you have that much head room it shouldn’t be to hard. If no rebar I would think solid. Others will be along with their thoughts.

    I saw a house being built with a 6’ crawl space and I asked the builder why not put the house just a little higher and they could have a basement. He looked at me like I was crazy and said we don’t do em like that.

    As you go around the country you see a lot of crazy differences in how they build.
     
  9. Jan 16, 2018 #9

    nealtw

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    I am late to the party but I would dig down and do the footing and pier to above ground level and then put in a 6x6 treated post
     
  10. Jan 16, 2018 #10

    Sparky617

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    Q
    In my area of NC basements are pretty rare. I have one, a walkout with poured walls and 10' ceilings. I have neighbors with crawlspaces well over 8 feet high, but the floors aren't level and are just earth covered with plastic.
     
  11. Jan 17, 2018 #11

    matty

    matty

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    The specs from the engineer do not specify that is needs rebar in it. It just states a fully grouted CMU pier. The info in the blue at the top is basically the report that i received from him. Nealtw, i was going to ask if i need to make the CMU Pier up to the same height at the others, or if i could just carry the blocking that specified from the beam to the floor, from under the floor to a pier, that is maybe only a few blocks high. IE pour the footing, do the pier up two or three blocks high, then block from there.
     
  12. Jan 17, 2018 #12

    nealtw

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    Other piers are deisign to hold the house straight and square so just post to hold up a beam should not be a problem. a question for the engineer. But some engineers have what they are use to is the only way.
    And more than a 4" footing
     

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