Drilling and anchoring into rock

[mark32]

I have to mount a landscape lighting transformer on a customers house but the side of her house consists of large, smooth round rocks. I think they're called river rock. Should I attempt to drill into the rock or stick with the seams? I was planning on using plastic anchors or tapcons, although I may have to use tapcons because I don't believe I'll be able get the transformer flush to the mounting surface.

 

[walkerj]

If it's just one, I think with a new masonry bit, you should be able to mount anywhere you want.

 

[PetrosA]

In my experience, it's better to drill into the rock if you can. Mortar can be weak or even just skin deep (on older houses there often is just mud behind the mortar that won't give you any grip at all). What I try to do is find raised spots behind the mounting holes that will give me a nice plane to mount to. If I can three out of four and the fourth ends up in mortar, that's ok. If there's a high spot behind what I'm mounting that causes it to rock, I might put the chipping tip in the Hilti and chisel at it some.

If you can't get a decent plane to mount to, you might have to look into using something other than the house. It's not cheap, but I know they make S.S. channel...

 

[JES2727]

I was told once by a Hilti sales rep that the mortar is stronger, because it's compressed. That may not be the case when you're dealing with irregular surface like rock.

 

[PetrosA]

I was told once by a Hilti sales rep that the mortar is stronger, because it's compressed. That may not be the case when you're dealing with irregular surface like rock.

Compressed by what? Is the mortar at the bottom of a wall stronger than that at the top? This sounds like snopes material to me. If anything, the mortar mix and (specifically) the ratio of cement or other binders in it is going to have more bearing than anything else. The most important thing is to get a clean, even and correctly sized hole in a material that won't crack or crumble. I'd probably not try to anchor into some flaky stone types like limestone or serpentine or shale without over sizing the hole and using some kind of filler cement around it.

 

[mark32]

Thanks for the replies,

PetrosA, I like the idea of chiseling the high spots, I didn't think of that. Unfortunately my Hilti doesn't have the chiseling option, maybe it's a good time to pick up a masonry chisel. Thanks!

 

[eds]

Is this the type of rock that is attached to a wire screen that is stapled to the house. I have seen this around here quite a bit, instead of a 4 to 6'' rock set on a brick ledge they staple wire mesh on the house butter the back of the stone and stick it on. I have drilled into these with a hammer drill and the stone has come off.

 

[mcclary's electrical]

A hammer drill on these stones will most likely make them falll off

 

[jcole]

Same thing happen to me that eds is talking about. I just built a pedestal with some channel and pipe and mounted the transformer to it.

 

[Dr.Sparks]

I would drill the mortar joint and set 1/4" threaded rod with epoxy and with fender washers and nuts, it can be leveled. Drilling into the rock itself will most likely create enough vibration to loosen the bond to the house and using any kind of expansion anchor in the mortar joint will most likely cause cracks..

 

[mark32]

Yes, I too thought about the possibility of the rock loosening up as I drill into it, blah, this was suppose to be a 5 min job.

 

[Ohmy]

Use This

Use This

Use one of these and mount off the wall

http://www.homedepot.com/webapp/wcs...nktype=product&storeId=10051&ddkey=THDSiteMap

 

[zbang]

I'd probably use some unistrut- dig a hole, drop some concrete in, drop some strut in, (wait), mount transformer. It'll look lots better than a cock-eyed transformer.

 

[eds]

I usually find a morter joint and if the stone is 1/12 to 2'' in thickness then I will use a 2 to 3'' deck screw. Usually you can drill through the mortar with a new bit and not set the drill on hammer.

 

[JohnJ0906]

4x4 pressure treated post.

 

[Cow]

4x4 pressure treated post.

I agree. Take 5 min to dig a shallow hole for a short post and you're done. If you try and drill the rock/mortar and chip out a big chunk, you'll probably end up sinking a post anyways....but you'll be PO'ed to boot!

 

[PetrosA]

Yeah sorry... I was thinking a real stone house, not a look alike

 

[mark32]

Thank you for all the replies, a post sounds good too. The rock looked like the real deal to me, it's on a large home in a pricey neighborhood, although I didn't pay as much attention as I should have as the owner gave me the most horrid directions, which put me 40 minutes out of my way and even worse I got pulled over and issued two tickets (Failure to register) so I wasn't in the best mood when I finally showed up at the job.