Anchoring to fieldstone foundations

ChrisJ

I thought I started a thread about this, but it doesn't look like it.
Old age I guess..........

How does anyone anchor to a field stone foundation? Is there a safe way? Can you actually hammer drill into a stone and drive a tapcon in? My electrical service is mounted to a tongue and groove wood wall that's anchored to the floor joists and, best I can tell, the stone foundation but I can't really see back there and it's over 100 years old (The wood, not the service).

I need to install some new walls between peers until my crawl space and one side of each is stone wall. I'd like to be able to anchor to the stone, if possible.......but right now I'm scared to touch it with a hammer drill honestly.

So,
Anyone on here drilling into stone foundations? Is it something that used to be done, but is now avoided? What's the story?

Larry Weingarten

Hi, I'll just put out a few thoughts. It's all guesswork without knowing a lot more about the job. So, how about gently drilling oversized holes and using epoxy to attach anchors? Or, skip that and use steel between wooden frame members to bridge the gap and create a place to attach new framing. Or, pour concrete to create new strong points of attachment. 🤔
Yours, Larry

Jamie Hall

I'd use -- and have used -- a diamond core drill and expanding type anchor bolts (there are several(. Pay attention to the kind of rock you are attcking Gneiss or granite are really good. Schist... sometimes. Limestone or marble OK. Some sandstones are OK, others not. Slate is OK perpendicular to the cleavage, but not parallel, and shale... nope.

ChrisJ

Jamie Hall said:

I'd use -- and have used -- a diamond core drill and expanding type anchor bolts (there are several(. Pay attention to the kind of rock you are attcking Gneiss or granite are really good. Schist... sometimes. Limestone or marble OK. Some sandstones are OK, others not. Slate is OK perpendicular to the cleavage, but not parallel, and shale... nope.

I'm not sure what's in there but I know I've found enough quartz when digging in the basement to make me very unhappy when I put in both sump pumps. I had to drill and bust chunks out and it was fun.

So I'm betting there's a decent amount of that in the walls.

hot_rod

Hilti has a lot of different solutions from epoxy insert tubes to screws and anchor bolts. It's kind of their speciality. Check their offering online.

I hear the Hilti "screws" work better than the Tapcon brand. I have had mixed results with Tapcons

ChrisJ

Larry Weingarten said:

Hi, I'll just put out a few thoughts. It's all guesswork without knowing a lot more about the job. So, how about gently drilling oversized holes and using epoxy to attach anchors? Or, skip that and use steel between wooden frame members to bridge the gap and create a place to attach new framing. Or, pour concrete to create new strong points of attachment. 🤔
Yours, Larry

The wood framed walls basically span a gap between the foundation(s) and float above frost. I'm using stainless sheet to go a foot or so under ground for rodents etc, but I need something on the stonewall side to keep that end from flapping in the wind, so to speak. The walls I'm building are just going to be 2x4's and plywood, with the stainless skirt below ground.

I was just going to anchor it at the top to the house it self, but it would be nice to have something down lower as well.

MikeL_2

  We do a lot of anchoring into various types of stone, blocks, bricks, cement, concrete, etc. Our rotary hammer drill works well with several drill bit sizes, depending upon the anchor bolt or screw needed.
   After drilling to the correct depth, we'll use a molly, shingle, or whittled piece of PT lumber snugly fitted &  driven into the hole & cut flush. 

mattmia2

Keep in mid its strength is mostly in horizontal compression, not vertically, so if you anchor to it and someone say trips and falls in to the wall, you could end up puling the stone you anchored to out, so it would be more for securing small items like conduit or boxes or something like that, if you anchor a wall to it I think you would want to anchor it to the framing at the top and to something at the floor, I don't think you want to depend on the foundation for support.

STEVEusaPA

I'd pour a concrete base if you don't have one, and anchor into the base at the bottom and whatever is up above.
You can do the epoxy anchor thing, but drilling into granite/mica, is not easy, as it usually just starts loosening up joints. Unless the wall is very thick. Then maybe you can find some anchor points.
100 years ago, they just cemented wood into wall and nailed to it. Don't ask me how that even worked.

ChrisJ

@Jamie Hall @hot_rod @MikeL_2

Is it safe to drill into a 150 year old foundation in regards to the mortar? A lot of mine is already falling out like dust. I think that's my primary concern. I don't know how important that is regarding structural integrity or if it's just for sealing.

ChrisJ

STEVEusaPA said:

I'd pour a concrete base if you don't have one, and anchor into the base at the bottom and whatever is up above.
You can do the epoxy anchor thing, but drilling into granite/mica, is not easy, as it usually just starts loosening up joints. Unless the wall is very thick. Then maybe you can find some anchor points.
100 years ago, they just cemented wood into wall and nailed to it. Don't ask me how that even worked.

Thank you for commenting @STEVEusaPA

That's the thing..........these walls I'm building are above frost so I can't pour concrete, at least not easily without trying to dig down 36+ inches under a crawl space. Currently there's just wood walls almost flapping in the breeze as it is. I'm just trying to make mine better.

mattmia2

STEVEusaPA said:

I'd pour a concrete base if you don't have one, and anchor into the base at the bottom and whatever is up above.
You can do the epoxy anchor thing, but drilling into granite/mica, is not easy, as it usually just starts loosening up joints. Unless the wall is very thick. Then maybe you can find some anchor points.
100 years ago, they just cemented wood into wall and nailed to it. Don't ask me how that even worked.

I have seen lots of structural brick buildings where a course of brick is replaced with a piece of 2x as a nailer to anchor to every say 4' or so. It works well as long as the wood doesn't get wet and rot.

Rubble foundations usually were dry laid, the mortar was usually added years later by someone trying to seal it up some, it usually isn't structural. It would be perfectly ok to remove some an put a bolt or rod in and replace the mortar as an anchor point. Be careful that you use a soft mortar mix so it can move with the stones.

ChrisJ

mattmia2 said:

I'd pour a concrete base if you don't have one, and anchor into the base at the bottom and whatever is up above. You can do the epoxy anchor thing, but drilling into granite/mica, is not easy, as it usually just starts loosening up joints. Unless the wall is very thick. Then maybe you can find some anchor points. 100 years ago, they just cemented wood into wall and nailed to it. Don't ask me how that even worked.

I have seen lots of structural brick buildings where a course of brick is replaced with a piece of 2x as a nailer to anchor to every say 4' or so. It works well as long as the wood doesn't get wet and rot. Rubble foundations usually were dry laid, the mortar was usually added years later by someone trying to seal it up some, it usually isn't structural. It would be perfectly ok to remove some an put a bolt or rod in and replace the mortar as an anchor point. Be careful that you use a soft mortar mix so it can move with the stones.

"Rubble foundations usually were dry laid, the mortar was usually added years later by someone trying to seal it up some, it usually isn't structural. It would be perfectly ok to remove some"

curious if this is a fact?  It would make me a lot more confident.

Jamie Hall

Sometimes the motar did stabilise the foundation -- some. But not much. There are a lot of fieldstone foundations around here -- some with house gone for a cuentury -- which are still standing just fine, thank you.

I might add, uselessly, that the mortar which was applied so hopefully on the inside didn't seal them up much -- either against water or critters...

EBEBRATT-Ed

There are a lot of stone foundations in with no mortar and they have been there for years.

My uncles house has a granite foundation with the stone put in with mortar. I had to core drill a 2" hole in it for a new electrical service some 30 years ago it was over a foot thick. Not fun. I did it with a core bit with a rotary hammer drill. My hands are still vibrating.

clammy

Usually I use in field stone and hollow block 3/8 expansion anchors with usually a3inch stainless bolt and a uninstrut L bracket . The L bracket allow you to be spaced off the wall about 2 1/2 inches . Personally I’m not a big fan of tapcons when given a choice cherry rivets lead shielded nail ins ,expansion or wedge anchors they all have there place it’s like sheet rock screws for screwing 3/8 plates duh sheet rock Oi. Worse comes to worse just hang off the ceiling joists w side beams and rod . I ve done this when the field stone is so out of level that there was zero way to have your pipe run straight and make anything square it’s more 3/8 but you can make it presentable instead of looking like thrash . Using anything less then a real hammer drill is silly even though I have a battery hammer drill when faced w field stone or rock containing quartz I pull out the plug hammer drill it has much more balls and drills it like butter

Peace and good luck clammy

EBEBRATT-Ed

People use Tapcons all the time, but I don't have a lot of confidence in them and have mixed results. I do like the lead nail ins. They always seem to work. Good for electrical conduit clips and mounting boxes.

With the lead nail ins if you read the box I don't think they are approved or recommended for overhead use. They work good with F & M plates though.

pecmsg

Horizontal, nothing wrong with tap cons. 

They are approved for overhead but at that point I’d go 1/4” or larger double expansion. 

Jamie Hall

I beg to differ on Tapcons. In concrete or mortar they work well. In some sandstones or low grade metamorphics they work well. If you field stones are high grade metamorphics or -- worse -- granite or basalt, they just won't hold even if you can somehow persuade them to go in.

PC7060

SDS or SDS Max rotary hammers are the only way to go especially for core drilling. 

I bought a Bosch Bulldog SDS after seeing one used to drill a 1/2” hole through 8” poured concrete wall in well under a minute. 

I’ve used it with coring bits of up to 4”.  

Harvey Ramer

I've drilled through quite a few limestone walls. 2+ feet thick. For large holes, 3-4" ect. I use a dry core bit. Mortar is usually decent on the exterior and interior 5" or so, but the center is a crumbly mess. I wouldn't be scared to use up to a 1/4" bit with a hammer drill on the larger rocks. Smaller ones it could knock loose. You can always use a tile bit if the rock is super hard. Tapcons don't work well in rock. Inserts and screws do. 

ChrisJ

PC7060 said:

SDS or SDS Max rotary hammers are the only way to go especially for core drilling. 

I bought a Bosch Bulldog SDS after seeing one used to drill a 1/2” hole through 8” poured concrete wall in well under a minute. 

I’ve used it with coring bits of up to 4”.  

That's what I use. I think I bought it back in 2016.

Mad Dog_2

Hilton Double expansion shields...Mad Dog 🐕 

ChrisJ

Mad Dog_2 said:

Hilton Double expansion shields...Mad Dog 🐕 

Have you drilled into field stone?  Curious on your experiences with it.

Mad Dog_2

Absolutely...Since in started in mid 1980s, I use

1)  "drop in anchors" (Hilti....Used with a driver bit ) hit by a Lump hammer for Hard, poured concrete.
2) Hilti Double Expansion shields for EVERYTHING else....

Never an issue.  I've hung very large diameter and heavy pipe with both, as long as they are sized for weight rating.

I've used old, style lead shields, Tap Cons, Thunder Heads, Epoxy Type...They all work, but I stick to what has always worked for me.  I've hung pipe and heating units over heavily-trafficked areas in the NYC Subway and The Financial center.  If these shields pulled out, people WILL be maimed or killed.  I sleep 💤 well using them.  Mad Dog 🐕