setting out foundations

[prideram]

hi , i am setting out some foundations but need them to be square with the orignal house, do i use the 3,4,5 measuring technique to make sure that it runs true and comes off the house at 90 degrees ? i was told that if i measure 4m along the house and if i come off the house at a true 90 and measure 3m then the differance between the 3m point and the 4m point will measure 5m

[mearlz]

Using the 3,4,5 triangle does work on short base lines, but increasing the size of the triangle to say 6,8,10 would make the line more accurate. When taping these distances they must be horizontal distances e.g. not on a sloping site.

This method does work but problems can arise and additional checks must be made e.g. the diagonals.