I have roughly dug out the footings for my new conservatory, i am hoping to set the levels tomorrow before pouring the concrete this weekend. I want to ensure the footings will be square to the house wall and also the the walls will be square to each other. If the size of the footings are 5550mm wide and 4000 from the house wall to the exterior of the new walll, do i then measure from corner to corner to see if its square ? And if so, what should the measurement be ? I cant decide how i would go about working this out. Any thoughts guys, and galls Cheers.

the diagonal measurement, provided all the corners are square should be 6841mm. measure both diagonals to get a more accurate measurement. we use the 3,4,5, theory to check or set out square buildings.it too is based on pythagarus's theory. if one side measures 3 units the adjacent side measures 4 units then the diagonal will be 5 units.

Hi Noseall Yes i worked out the 6841 myself in the end. I have now adjusted all the lines and to be honest, they werent that far out. But as you state " so long as all the corners are square" So measuring the diagonals still isnt sufficent to say the marked out area is square then ? this 345 rule, if i knock up a few bits of 3x2 and make a blooooody big triangle, then place that against the wall, is that what your saying ? Thanks for taking the time to respond by the way...

yes, if your diagonals are to within say 5mm of being equal then you've cracked it. you can measure the adjacent walls to check the 3,4,5. you can measure 3mm, 3inches 3 feet or 3 metres, you don't have to go all the way to the next corner to check, though the longer the increments the more accurate it will be.

Ah got what you mean now. So lets say i measure 3 feet of the exsisting wall and put a chalk mark, then 2 feet up the line i have just laid down and again a chalk mark, I then measure between these 2 points and it should be 5 feet. easy when you explain.. Cheers noseall. now i know how you got your name

almost there. the increments are always 3,4 and 5. so it's 3 feet along the wall, 4 feet up the line and 5 feet will be the diagonal between the marks. look at the square(ish) tele or monitor for example. starting from a bottom corner, measure up three inches, put a mark, measure across four inches, put a mark. then the measurement between the marks will be five inches if the monitor is 90 degrees.

Hi Noseall, Yes sorry slip of the finger. 2 was meant to be a 4 Cheers once again for taking the tiome to sort this...