Saturday, May 20, 2017

Finding the Centre of a Building:- using the old-fashioned plumb-bob technique

Often my students ask how to find the centre of a building, especially when it's a weird, uneven shape. To do this you can emply an old-fashioned low-tech technique using gravity, that really works very well. You don't need to 'fill-in' the 'missing corners'...

You will need:
- a print out of the plans
- a pin-board or piece of foam
- a sturdy pin
- a length of cotton or thin string
- a plumb-bob or something heavy to weigh the cotton down
- ruler
- pencil or pen (with ink that flows out easily)

1. Cut the floor plans all around the edges.
2. Insert the pin through one corner of the plans and let them hang freely.
3. Pin the plans onto the pin-board/foam.
4. Attach the plumb-bob or heavy object (such as a nut) onto the cotton and make a loop at the other end (I used an old fashioned metal baby pin).
5. Hang the cotton/string on the pin:


6. The line will hang down exactly vertical across the plans, now use a ruler and pen to mark the line:

7. Continue to do this all around each corner of the plans:

The green pen marks the plumb lines, the red pen was my guess for the centre, it turned out they were the same:

8. Voila! Now you have the centre!

There are other techniques you can use as well, but this is the simplest and you can really see it's a hands-on technique :-)