On Sat, 25 Sep 2004 14:59:09 +0100, IMM wrote:


"Andrew Gabriel" wrote in message

The part in the loft usually isn't though. Gable-end walls are
notoriously weak,

What are you on about? they have the same foundations as the other walls.
I have mounted boilers on gables and never had any problems. Boilers are
not that heavy to worry a gable end.


The foundations are the same as you say. Problem is with top ends of walls
which don't support anything above.

I'm not a civil engineer - I'm thinking this through as a physicist, so
obligatory hypothetical situation - but bear with me he

Take a pile of bricks and construct a 6ft high by say, 4ft wide, 9in thick
dry wall (no mortar or other filler) on a stable level surface. Kick the
bottom - I would wager a fiver you'll hurt your foot before you move any
bricks due to the weight holding them in place. Try nearer the top -
should be able to knock out a load of bricks easily because you only need
enough sideways force to overcome a little friction.

Add mortar - that will scale the strength up by providing adhesion and
better interlocking, but strength is still a function of internal load -
and the top end of a wall carrying nothing is thus considerably weaker
than a loaded wall or the base of the same. The combi will be hanging off
one side of the wall giving you a significant turning moment which only
needs to overcome the adhesion of the mortar and the weight of a few feet
of bricks.

I have no idea how heavy a combi is - but I'd consider it worthy of
further investigation before hanging it up on a gable end. What's the
typical weight of a small combi out of interest - and how deep is one?

I won't contest that you've done it and it nothing fell off - but I
wouldn't be so happy about doing it myself without a second opinion.

Cheers

Tim