Lintel encasement understanding.

[rednaxela]

Hello All,

I would apreciate some help in understanding the following;

When drawings specify e.g. 203x133x25kg UB encased with 12.5mm boards and skim.
Does encasement mean just seperating it from the living spaces in case of fire?

i.e. Encasement = The lintel sits between the joists with the wall above and ceiling below consisting of 12.5 board and skim.

or Encasement = The sides of the lintel are also clad in 12.5mm boards and skim and then the ceiling is fitted with 12.5mm board and skim? i.e the whole lintel is encased within the ceiling cavity.

Many thanks,
Alex.

 

[freddiemercurystwin]

I believe (off the top of my head) that just 1 layer of plasterboard wont technically give any fire protection (not that would comply with building regs) but you need to check with whoever has done your drawing. So I would think that only the exposed portion of the UB would need to be clad. Best to check with your draughtsman though really.

 

[^woody^]

A steel beam or lintel needs to be protected from the heat of fire to prevent it failing and causing the walls or floor it supports to collapse too.

The amount (ie time) of fire protection depends on the beams' function and what it is holding up, so thickness of protection varies

Whether this protection is done by physically encasing the beam or putting the beam within a floor void, is dependent on the design and its function. So potentially, a beam may need additional protection even if in a floor void, or just the protection of a plaster ceiling may suffice. Speak with the designer

 

[noseall]

in domestic scenarios where i have fitted a steel beam and this has been within the floor space, building control were happy with the ceiling layer of 12.5mm boards and skim to provide adequate fire protection.

but not all requirements/scenarios are the same, so check with b.c.

 

[^woody^]

Yes thats on of the quirks or the present system, in that if you had dropped the beam so it was below the ceiling, it would be most likely that the BCO would want additional plasterboard or some superlux or something.

 

[rednaxela]

Thanks for all of your advice.
I will have to check with building control, as the plans show the lintel below the ceiling level, but the builder put it into the cavity so that I would have one ceiling span. It does look nicer.

That has all been inspected, but I will be putting ceilings up soon and the drawings don't match up now, hense my questions.

thanks again,
Alex.