Knocking hole in wall for big extract fan - need a lintel?

[reg091]

Small (2mx2m) utility room with flat roof. Cavity wall (block inside, brick out). I need to install a large (250mm diameter) extractor fan in one of the external walls.

It will be quite high up, so in terms of the load from above the hole it will be approx 5 coarses of brick, and maybe a ceiling joist for the flat roof if one happens to be above that bit of wall.

Lintel? Seems unlikely to me for such a "small" hole.

Or I could make the hole square (say 280mm) and put a strong wood box tunnel in.

Any advice welcomed.

 

[Bonni]

I wouldn't bother with a lintel. A brick is 215mm, at worst, the most that can fall is one brick assuming that full brick is fully over the opening. Just a thin box to close the cavity is needed.

 

[rsgaz]

Just drill the hole. Circles are naturally strong and distribute load well, just look at viaduct/bridge/building arches.

Square would be weaker.

 

[^woody^]

 

[stuart45]

You should have measured the fan first woody.

 

[pilsbury]

View attachment 148707

Even in that hole it only looks like 1 brick could fall.

 

[Newboy]

That's what happens when you use a howitzer instead of a core drill