few newbie questions

[grahama]

Hi Tony,

the max span I can get due to existing window openings is 3.6M . He has specifies 8x5 steels on both skins at 25kg/M (think that is how it is measured).

Have got a thick booklet full of calcs and he went through why he had used what he had used and why I couldn't have the 4M steel opening I wanted, but it is only 40cm narrower so not too bad.

regards,

Graham

 

[tony1851]

On a 3.6m span with normal domestic loading, I would have gone with two 8x4s, which is little different, so I don't think you have an issue there.
Some posters on here have been lumbered with much heavier beams than that!

When he explained about the slightly reduced span, was it concerning the proportion of wall left? The Building Regs use a rule of thumb of not taking out more than 2/3 the width of the wall. You can actually take out more than that, but the council then ask for calcs to prove lateral stability of the house, which can be a bit involved.

Compared to some on here, I don't think you've had a bad deal with your SE.

 

[grahama]

The span was indeed related to the 2/3 rds rule Tony.

We have to have a nib extending into the new room to place the beams on and we are making a false chimney breast so that will be disguised. Flush the other side so works out just about right.

I haven't looked into the calcs in detail yet but I am pretty sure the 3.6M opening span is plus the 150mm each side for resting purposes, so, 3.9M in all. Will just buy a 4M steel and have more on the padstones.

Regards,

Graham