A Question out of Ignorance

Discussion in 'Heavy Equipment & Pavement' started by cddva, Sep 13, 2006.

  1. cddva

    cddva LawnSite Member
    Messages: 189

    I had a person call today to ask if I could dig a footer for an addition on their house plus do some grading of the yard. I have very little "building" experience and have no experience digging footers but.....would certainly like to learn and expand my part-time services to include digging footers for something of this scale. So, my honest Abe response was to say that I have not dug footers for a house before but I would be willing to come out and look at the job. He left it that he was still a few weeks from needing the footers dug due to more demolition work needed and he would keep me in mind (I figure I probably lost him as a potential customer). However, I'm hoping some of the knowledge base here may give me the insight to either stage a comeback or just forget about digging footers. Now for the ignorant question, how do you dig a footer for a house? Meaning, what survey points or lines do you follow to locate the footer correctly and dig to the proper depth, how wide should the excavation be, etc.? I know codes dictate some of these answers but the blue prints should have this info and I would assume the site is marked with this info for the operator, right? I would be willing to rent a mini-ex for the job but obviously need to know what I'm doing as far as the actual digging. Would appreciate your good coaching skills on this one! Please keep the laughter to a low roar.....you have to start somewhere right?:laugh: BTW, I'm too old to start in the trench's with a shovel (did some of that during high school years - I was the boss mans' mini-ex). Thanks.
  2. Bill Eh

    Bill Eh LawnSite Member
    Messages: 37

    Yes the plans would spec it out. Batterboards can be installed by the contractor to provide guidance. If you are expected to do that you'd better be good at geometry. Prepping a footer base may require hand labor to ensure the base is down to solid under lay. I love doing that stuff.
  3. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Messages: 9,544

    For most foundation digs the excavation contractor specifies the building contractor has to be on site to help with the foundation. For most of our foundations we have to dig down to hard material mainly solid rock or hard pan.

    The thing you will need is a good laser level and a grade stake with the sensor once. Or if the contractor is there they should have one and they check the grades.

    A house needs to start out square and level so if the foundation is out of square then the rest of the house will be tough to make it square.

    The forming contractor usually does all the hand digging and finicky work they are responsible for that. Also in my area every foundation has to be engineered so you don't want that responsibility of taking things into your own hands.

    When digging foundations especially with a small machine is think ahead do everything that needs to be done before you move. You get a part dug out and you missed something its like oh **** now you can't reach it.

    Another thing to watch for is the ground conditions you have keep a eye on cave in's etc. Say your digging a trench and a big chunk sluffs off its a sign to make the trench wider than normal. Also if the ground is really bad and it requires shoring to hold the bank up you need to make the trench wider to accomodate it.
  4. Electra_Glide

    Electra_Glide LawnSite Member
    Messages: 75

    I do excavation for some of the local remodeling guys, and I always require them to do the mark-out (usually we mark it out together, but it's their job to read the plans and the tape measure, and I just double-check it). They provide me with "dig-lines" that show exactly where they want me to dig. Usually, these are white lines painted out on the ground (which we have to do for the utility mark-out anyway). That way I don't have to worry about offsets, overdigs, etc.

    We then have an on-site meeting the morning the job starts, and go over EVERYTHING before turning the first shovel-full of dirt: markouts, overdigs, footer depth, footer width, floor depth, where to put the spoils, site access, etc.

    I then start digging to establish the floor and bottom-of-footer elevations. As soon as the elevations are set, we meet again and they will verify the elevations. Once they're happy with that, I'm off and running, and they're free to go about their business. If there are additional elevation changes somewhere in the excavation. All work will again stop once the new elevation is established and is not restarted until the elevation is verified by the GC.

    You have to make sure you are digging straight, plumb, and flat. Otherwise you're going to run into problems. The best way to ensure you're digging straight is to get yourself setup on the line such that every time you move you don't have to turn the machine. If you move straight back, your trench will be straight. The best way to ensure you dig plumb is to make sure you're set up on a level pad. (A good trick here is take a level and lay it on the floor of the cab.) This becomes more critical the deeper you go, since if you're not digging plumb, the bottom of your trench could end up way off from where you started. The best way to dig flat is to get close to your final elevation, and the "slide" the bucket along the bottom of the trench. DO NOT overdig. Footers should be poured on undisturbed ground. Get out and check your grade (or have your stick man do it) before you think you're close. If you're too high you can always take out more material. Once you're too low, you're screwed. You want to be using some sort of a rotating laser for all your elevations.

    And lastly, think before you dig. Like Gravel Rat said, with the limited reach of a mini, you need to plan your moves accordingly (especially if you're going beyond a few feet in depth), because you will run out of reach quickly. And if you can't reach what you need to dig, you'll have to become very familiar with the "manual backhoe" technique.

    Strive to do the job such that there is no need to send a man into the trench when you're finished. Inevitably it happens, but if you are careful , and take your time, there should be minimal shovel work.

    PM me if you have any questions. Good luck...

  5. AWJ Services

    AWJ Services LawnSite Platinum Member
    from Ga
    Messages: 4,281

    If it is a small job I would suggest pick and shovel for your first dig.

    I also start at the lowest point in the footers and dig from there.
    Once they get over 8 inches deeper than when you start you do a step up.I usually have a guy with the laser detector on a pole checking as I go and telling me what too do.
    If you have a boom offset on Excavator you can pull a string and dig down it too keep straight.
    It really is not that hard.
    The old timers use flour for marking lines instead of paint.
    We still do alot of block walls for crawl spaces.
    All of our basements are poured and there footers are done a little different.

    Most counties here want an 18 or 20 inch wide footer and the thickness varies.

    Some require bar in places and some want bars on step downs.
    That will be up too your county.

    The footer guy here actually will do the batter boards and most of the measuring too plans.
    He marks everything as well.
    The builder or contractor basically just verifies the location.Some builders do it different.
  6. xcopterdoc

    xcopterdoc LawnSite Senior Member
    Messages: 752

    we have a guy here in town that uses old Case track trenchers to dig footers. The chain is set for 18 inches wide.
  7. murray83

    murray83 LawnSite Senior Member
    Messages: 347

    i love that bullet level idea,can say i've never thought of that especially since i use a backhoe.
  8. Electra_Glide

    Electra_Glide LawnSite Member
    Messages: 75

    Unfortunately, I can't take credit for the original idea, since I picked it up from another forum.

    It's much easier to get a backhoe level since you can adjust each stabilizer independently. If you're using an excavator, you have to be sure you're on a level pad.

  9. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Messages: 2,454

    I kinda do what Electra Glide does with my track hoe........I have super glued a small string line level on the right side of my cab and one on my front wind shield metal area that I can see between two foot control sticks. They are not distracting and are a good reference point......I also have a blade on my machine and if I can't find a level spot or grade the dig area flat first, I position my blade on the low side of the dig and use that to level me out for that line......

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