In uk.d-i-y, A K wrote:
I have a house that is 1 year old. In the lounge I have 2 bog
standard ceiling pendants. I have bought some new light fittings and
got an electrician to come and fit them (yes I am a hopeless girlie
when it comes to DIY!). When he unscrewed the pendants he had found
that the hole had been filled completely with expandable foam
together with all the wires. he said that it would be a whole days
job to do the lights as he would need to get all the foam off the
wired and would then need to test to make sure he hadn't damaged
them.

This isn't the "good workmanship" required by wot us old(er) farts
call The Wiring Regs and is now British Standard 7671:2001 with the
2002 Amendment (if you want to use that formal title to help bully
your builder/seller ;-). It makes it (as you just found) impractical
to fix faults or change the fitting. It's harder to argue it's an
actual fire hazard - the foam probably isn't flammable - but (ah!
here's an argument!) it certainly makes it (a) impossible to inspect
that the screws holding the wires are done up tight, and (b) to
tighten them if they're loose. And if they are loose, the places
where they make contact will get hot, and maybe spark.

The lazy gits wot did this had plenty of reasonable ways to secure
a normal ceiling rose: they could have put in a plasterboard back
box, used plasterboard/cavity fittings to secure the rose, or put
in a little wooden plate running between the two nearest joists
into which they could've screwed the ceiling rose. There's no
reasonable excuse for the magick-foam trick.

(Obligatory regulatory whinge: and *these* bodgers are considered
Competent Persons by the forthcoming "you toucha your wires, you
paya da guy with the Stetson, spurs and horse 75quid to say it's
no worse a bodge than he'd'a done" regulations... sigh.)

Getting the builder to do the decent thing may be a bit of a struggle.
If they try to fob you off at first, see if you can find more fittings
bodged this way: it's safe to unscrew the covers on ceiling roses if you
switch off all the power in the house, and almost as safe (just as safe
unless there are some *really* unsafe bodges!) if you just isolate the
relevant lighting circuit at your consumer unit ("fuse box"). On a 1yr
old property the circuits in the consumer unit should be clearly labelled,
and turning off a whole circuit should mean just pushing a small button
or lifting a little switch-looking-thing on the MCB ("miniature circuit
breaker" - modern replacement for a fuse) which controls the circuit.
Look for this foam-fix-bodge both in your own house, and (if you know
one or two of them) your neighbours'. The more widespread the bodge is,
the more ammunition you have with the builder/developer when you mention
how interested you think the local papers/DogWatch/NHBC/local authority
Building Control people might be.

Good luck - Stefek