Marking a level for new foundations

Discussion in 'Builders' Talk' started by woodworker, Feb 22, 2004.

  1. woodworker

    woodworker New Member

    I am about to put the hardcore and concrete down for my extension. I have tried marking out a level using wooden battons and a spirit level. The problems is that the ground under the house is solid clay and shale and I can't knock the wood down enough to make it stable. I have considered buying some steel spikes to get through the ground, however i need about 10 and they need to be at least 650mm long to be steady in the ground. Do any of you pro's out there have an alternative idea?
     
  2. limestone cowboy

    limestone cowboy New Member

    I think you've got the right idea with the steel spikes if you can't hammer timber into the ground. Have you got a laser level? They are the easiest way to get a trench or foundations level, especially if you're working on your own because you don't need anyone to hold the staff like with optical levels. Set the laser up where it can point at every peg you are putting in. Put a peg in with the top level with where you want the finished surface of the concrete or hardcore, then point the laser at it and measure the distance between the top of the peg and the dot. Now you can point the laser at where you want the next peg and hammer it down into the ground until the top is the same distance from the dot. If you put a peg every 2m or so you can guess the concrete level between them good enough to build off or you could use a batten. You can also use this method is you are spreading hardcore over an area under a solid floor but lay the pegs out on a grid. I've done this under factory floors of 200sq m.
     
  3. jmcbuilders

    jmcbuilders New Member

    Hi what are you building. If it an extension it should be at least 1m deep or down to virgin ground. Try just laying the concrete and level it. No hardcore under foundation
     
  4. Thermo

    Thermo New Member

    you could use a length of rebar for marking out, they are only about a pound each and could be left in the foundation once poured
     
  5. woodworker

    woodworker New Member

    I don't have a lazer level, and the extension is only 3m X 6M so can't really justify buying one for this job. Despite my best efforts Mrs Woodworker would not be pleased if I bought another tool! The footings are only 750mm deep which have been passed by the council. I hit hard ground after about 3 inches in to the dirt.

    Thermo what is a rebar and where do I get them?
     
  6. Thermo

    Thermo New Member

    sorry, rebar is short for reinforcing bar, the stuff you normally put in concrete. You can get 12mm bar from travis perkins which is 900mm long for £1.25 each. most builders merchants will sell it. It seems it would be about the right length to hammer into the ground for marking it out and getting the levels and then once youve got it set up you can just leave them in when you pour the concrete.
     
  7. Thermo

    Thermo New Member

    are you doing this for the foundations or for the floor slab by the way? If your doing it for the foundations then as jmc says dont use hardcore in there.
     
  8. woodworker

    woodworker New Member

    The reason I'm putting hardcore down is because I've got a 600mm trench to fill and if I use concrete I'll have to have abut 15 tonnes delivered. My driveway in on a steep gradient and it will go off before i have chance to barrow it up there. Also a mini mix wagon will fit up my driveway, whereas a big bugg3r will take out my wall out trying. Hardcore doesn't go off.
     
  9. Dewy

    Dewy New Member

    I thought redimix lorries had pumps now. They can reach most reasonable distances unless you have an extra long drive.
     
  10. eyetry

    eyetry New Member

    Get a cut down scaffold pole and drive this in. Give it a wiggle, remove it and put your timber profiles in.

    Wear gloves as the more you smake the pole [ooo-eerrr] the sharper the end will be.
     
  11. woodworker

    woodworker New Member

    Dewy, I asked about a pump on the wagon, apparantly there are a few dotted around the country but none in Sheffield. It would cost an aditional £300 to hire the pump as they only work for a minimum 6 hours. I am trying to save as much money as possible to justify my next workshop purchase to Mrs Woodworker.
     
  12. jmcbuilders

    jmcbuilders New Member

    You can not use hardcore in your FOUNDATIONS. You can pour it in two loads over two days as long as you cover the bottom completely and the second pour on top and level. 15T is only approx 6m.
     
  13. woodworker

    woodworker New Member

    JMC, why can't i put hardcore under foundations? Presumably it is just the same as putting it on to solid ground. I thought that as long as the depth of the concrete was to the specifications of the plans then hardcore would be a good way of filling the excess space.
     
  14. jmcbuilders

    jmcbuilders New Member

    Because it is classed as movable fill . Concrete when set is in one mass there four solid and will project is mass at 45 each side of the foundation. Also building insp will not pass it
     
  15. woodworker

    woodworker New Member

    Cheers for that JMC, it's taken me weeks to dig the hole. I'd hate to do it twice!
     
  16. limestone cowboy

    limestone cowboy New Member

    WW,
    I have to agree about the hardcore. I think a pump is a bit over the top and expensive for only 6 metres. I do some work in Sheffield and know what you mean about steep narrow drives. The last job I did like what you are doing I hired a small dumper to move the concrete. It worked out cheaper than pumps and labourers/barrows, and it didn't get tired.
     
  17. building control

    building control New Member

    Ring your local building control and ask if you can put hardcore under the concrete. after he finishes laughing order extra concrete.
     
  18. oggie

    oggie New Member

    Hey woody
    you heard of Screwfix ? laser level deal less than £30 all you then needed was a bit of 50x20 dressed and mark it out in 10 mm's highlight the meter! instant staff piece of ****! tell the wife you need it! good for dado's kitchens the lot.
    As to reinforcing rod great idea but keep it to the outside or inside of the trench walls as it can be classed as a weakener if put on centre. And no hard core however you can use it for under your slab as long as you blind and compact it
     
  19. woodworker

    woodworker New Member

    Lots of concrete arriving in the morning and two neighbours to help. Thankfully i've worked out that the lorry can reverse up neighbours drive and swing his chute across to within 6 feet of the footings. Hope the b1oody frost keeps away.
     
  20. oggie

    oggie New Member

    If you think youll get frost cover it with old carpet or saking hay even and it will be fine
     

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