HELP with Beam Width Please?

[EnglishBadger]

Hi

I have just read in a renovating book that beams should be no more than 60cm apart. In our 100 year old cottage, the beams are 100cms apart. Can we expect our bedroom to fall into the lounge soon?

[Gyn_Paul]

If you definition of 'soon' is 'between ice-ages' then, yes; quite soon.

[Gluestick]

If your cottage has stood for 100 years so far, it will probably still be there in a few years yet.

The function of the beams is two-fold: firstly and quite obviously, they support the upstairs floor.

Secondly, they tie the outer walls together and take out the load of the roof, normally via the cross-ties (which prevent the roof side timbers from spreading.

Imagine a triangle: the roof beams are the base.

Old builders used both experience (from those that did fall down: and those that stayed put!) to gauge material sizes and loads. They thus had access to a mine of empirical knowledge from thousands of years.

Safety factors tended to be massive; unlike today. That's why Brunel and Telford's bridges are still standing!

If you look at a modern house in the UK, you will see the roof trusses are very small section: buts there are lots of them.

The distance between beams is a function of the size of the beams: their length (since over length any material "Sags" with no load: this is called natural deflection) and the thickness of the flooring.

A good rule of thumb test is to stand in the centre (i.e. midway between the beam length) and jump up and down.

You should feel the floor deflect, marginally: that's normal.

If you suddenly arrive downstairs covered in dust and muck, then this would indicate that someone was wrong with the design!

Or you have severe termite, death watch beetle or woodworm infestation................

Sleep easy!

[:D]