Drilling into cinder/aerated block help

[sjalloq]

Hi,

I'm having a bit of a nightmare trying to mount some french cleats on an internal wall in my workshop. The wall is plaster over what I think is that horrible powdery lightweight block. I've got a couple of issues that I'd like some advice on:

1. I'm using a 10mm drill bit for the fixings I've got and the hole is coming out more like 11.5mm. I'm using an SDS drill. Am I better off driling an 8mm first and seeing if I can fit the fixings in that first?

2. I've hit a couple of voids or mortar joints that have crumbled meaning I have no chance of using the fixings. Should I just drill to the right or left by 2 inches?

Cheers.

 

[RossJarvis]

Are you using the hammer setting? I've found with a lot of masonry, this should be a last resort. With aerated blocks try gently at first and see if a bit will go in without hammer, it should do. Same with bricks, just push harder.

You can try 2 inches to the side, depends on the mortar gap. If possible further. Another issue is that some blocks, particularly soft ones will crack when an expanding fixing (wall anchor, Rawlplug etc) is tightened up, worse when near edges. You could just try a wood screw directly as this can hold on its own.

 

[sjalloq]

Yeah, was using the hammer setting which I think was overkill. I've now tried one with the 8mm bit and then I'm using an ordinary twist drill bit in a cordless drill to take it up to 10mm. This seems to be the way to go and the hole is a lot neater.

Regarding the spacing, how much would you moving the hole if you hit a mortar join?

Incidentally, what is the best way to fill old drill holes in walls? Aside from this mess, the previous owner of my place seemed to like to drill lots of large holes. I have some plaster that is advertised to fill large holes and can also be drilled once dry - but I don't know how to pack it in to a deep drilled hole. Any pointers on how these sort of things are fixed?

 

[mind_the_goat]

If it is the really low density block you might want to try resin fixings, eg: http://www.screwfix.com/c/screws-nails-fixings/resin-fixings/cat840022

 

[sjalloq]

Thanks for the resin fixing tip. I'm using a Fischer SXR 10x100mm frame fixing and they seem to be biting well in the 'good' holes so far. This isn't going to be loaded too heavily as it's just going to be hand tools above my bench area. The other wall I have to drill is an old exterior wall, as this room is an extension, so that should be plaster on brick.

Perhaps I should have just put up a sheet of plywood and put cleats on that rather than 5 rows of cleats each with 3 fixings. Looks a bit messy now with the extra holes.

 

[SlowSteve]

For the Aerated blocks ( as opposed to the Lightweight ash/cinder blocks) then use a HSS bit rather than a masonry bit.

If you hit mortar, either shift 30mm left or right ( It's gamble every time)

For patching the holes - wait until all your own drilling is done then every hole you want to fill brush it with a mix of 5 parts water to 1 part PVA. If the holes are still dusty when dry, give then another coat - Then make a wet sloppy mix of 5 parts fine sand, 1 part cement and a load of PVA glue in it and mix it so it's like plaster in consistency. Give it a sniff and if you can't smell the PVA - add more. Put it on just like you would polyfiller with a scraper and then get a damp sponge and clean it all up.

If you've hit voids, then you can dig out the plaster and fill the whole void up with this mix - you can add about 1.5" depth at a time with this mix.

It's a good way to "reset" a room - gets you going from a clean slate. It looks ugly - pasty grey - but it paints nicely and gives a smooth finish.

 

[sjalloq]

Thanks Steve,

when you say 'dig out the plaster', do you mean to excavate a larger hold around the drill hole so that it's easier to back fill? And will this mixture allow for future drilling or is it only suitable as a filler to paint over?

 

[skipdiver]

http://www.toolfinder.co.uk/hardware/fi ... wwod7CAD6Q

I've had success with these type in thermalites and did you know that you can screw directly into thermalites with no plug at all? Also recommend using a normal drill bit and no hammer action. Using cut nails also work well in thermalites.

As for hitting the mortar bed. You need to determine whether it is the bed or perp joint you are hitting. If it's the bed then move up or down. If it's the perp, then move to the side.

 

[sjalloq]

Thanks Steve.

In all cases today it was the perp I hit although I guess the weakness and the way it crumbled could mean I was near a corner on one or two. I've now finished the wall and it doesn't quite live up to the vision I had in my mind. The cleats are level but that's about all I can say about them. Pic attached. Hopefully won't notice all the holes and misplaced screws once I've hung my tools on them.

Also, this was the first time I've drilled into this wall so didn't know it's construction. I bought the SXR plugs after a previous question had lots of suggestions on which fixings to use. I went with something that would work in a range of walls. I might drill a test hole behind the skirting on the next wall and see what might work best.

Cheers.

 

[skipdiver]

All's well that ends well.