by theelegantman »
Thu Mar 19, 2009 5:55 pm
Drilling into walls, especially for mounting TV's, is a specialty of mine. I have a wealth of experience with different building techniques and substrates but that being said, i learn something new from time to time.
I hope this long-winded response offers you some help.
If you are drilling through plaster into masonry, is there a gap between the plaster and masonry? Usually this would indicate a 'dabbed' wall, where splodges of plaster are used to fix the plasterboard to either a lightweight, compressed fuel-ash type or to a heavier blockwork wall or brick. If there is no gap, this usually indicates a rendered brickwork. As a general rule of thumb, if there's a gap and you're fixing something with a big 'moment' or leverage against the wall, a stud type fixing is best. If it's a soft substrate, a resin anchor is best suited as an expanding or sleeve anchor will not be able to acquire any 'grip' inside the masonry. If there's no gap between the masonry and the plaster, a decent sized screw with a 6mm diameter and a length of at least 60mm will be suitable with a brown rawplug. Make sure you bed the rawplug back into the masonry, otherwise all the compression (grip) will be too far forward and cause the plaster or masonry to 'pop'.
So now, we should be in a position to understand what you're fixing into?
In most cases, a masonry bit with hammer action, will happily buzz its way through any hard material until it gets to steel or if you're lucky, plastic. A tell-tale change in the noise the 'bit' makes will let you know that you're no longer drilling into what you thought you were.
If it's the case that you're drilling a short way into masonry or plaster and the drill bit stops, have a look above and below where you are drilling. Is there an electrical socket? Could be you've just been saved a great expense by the metal capping between the wiring and the plaster. If this isn't the case, you may be drilling into a steel support. Are you above a doorway or window? Get a bright torch and try and squint down the hole, if you see a reflection of any sort, i'd suggest drilling elsewhere.
I have known plastic piping to temporarily stop a masonry bit too, could there be a drainage pipe behind? Again, i'd suggest drilling elsewhere.
I really hope i've been some help to you, but i'll keep an eye on this if you have more info or questions.
