I'm anticipating a job where I'll need to fix a 4m long wooden beam onto
a rendered wall made out of these blocks

http://i115.photobucket.com/albums/n...psdmhzmcjj.jpg

I've done other drilling jobs on these and sods law some holes will hit
webs and deviate.

The chemical anchors designed for this sort of block have plastic
inserts a bit like a hair roller which gives the resin something to hold
onto whilst it cures. This means a bigger hole in the wall than the
studs (typically 16mm hole for 10mm studs)

I reckon I'll need about 8 anchors along the length to support the load
and currently the day temperature is about 30 degrees so I only have
minutes before the resin goes off.

What is the best technique for this sort of job? My current thinking is
to try and drill the wall first hoping to avoid a horizontal line of
webs, fit the studs one by one trying to keep them 90 degrees to the
wall, let it all cure. Then offer up the beam and mark the studs, drill
and attach the beam.

Normally I'd drill the beam first and use that to mark the wall but I'm
concerned about deviation of the holes in the wall due to these horrid
webbed blocks that the French seem to love.

Any advice please chaps?

tia

Bob