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'Audit' Issues with using Laser Levels for foundation/floor thickness

  • 12-04-2009 10:20am
    #1
    Carlow52
    Closed Accounts Posts: 2,389 ✭✭✭


    This post is just to pass on something, primarily to Self builders, I came across recently.

    Prior to the wide-spread use of laser levels, it was common enough practice to stick wooden pegs in the foundations to let you see how high u need to come with the concrete for say a 300mm deep footing.

    Different ideas were used for floors/subfloors the general idea being that there was a physical mark set before the concrete was poured.

    However the laser level has done away with many of these physical marks and it is therefore very simple to pour much less concrete than required in the spec and the finished product gives no clue as to the real depth.

    I twigged this for the first time when I happened to see the docket from the readymix truck.

    The strip foundation had only 200mm as opposed to 300, the first answer was that the ground was a bit softer due to rain in the open founds when they came to pour so they took out 100mm more:)

    Keep well.


Comments

  • #2
    Builderfromhell
    Registered Users, Registered Users 2 Posts: 1,570 ✭✭✭Builderfromhell


    Whether you use a laser level or not, it is normal to use steel or timber pegs to ensure the top of the foundations is all the same level. If foundation trenches have been dug level then the pegs should be a min. of 300mm from the bottom. Thye may be more thna 300mm in places but should not be less.


  • #3
    cork1
    Closed Accounts Posts: 443 ✭✭cork1


    im not a fan of fellas using laser levels they dont seem to as precise as the older method of the level you look through. well the level is accurate but the fellas using them arent. and your level is only as good as the operator


  • #4
    [Deleted User]
    Posts: 31,118 ✭✭✭✭ [Deleted User]


    I used a water level (I had the time!) when setting the foundations and erecting the rising walls, both the roofer and the floor screed contractor used laser levels.

    The master bedroom (furtherest away from the datum point) has the floor -1 cm lower and the ceiling ended up 2cm higher (total +3cm).

    All within tolorance, but just proves that lasers are not perfect! If both lasered levels had gone the same way then I could have queried my original water levels but they were opposite to each other.


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