Mounting bolts for stair rail — advice needed

[JHCC]

I’m working on a pair of railings for a short set of steps up to a porch. The steps themselves are a pre-cast concrete unit that appears to have mounting holes already cast into it. Those holes currently have some kind of cement-based filler, so I’ll have to drill that out before I mount the rails. 

My question is this: I’ve never mounted a railing to concrete before, so I’m not as familiar with anchor bolts as I am with, say, lag bolts in timber. Which of the bolts in the following photo would folks recommend, and why? Or is there something else that they’d recommend?

Thanks in advance.

[gewoon ik]

The middle once I only thrust for temporary. I have used them for temporary handrails at a construction site.

The left and the right i used for forklift protection rails at the shipyard

Worked ok, they came loose after the steel delivery truck backed up into them.

[Irondragon Forge ClayWorks]

I have used the left and center one's. The one on the left has been holding down the trip hammer at ESSA for at least 5 years now still tight. The problem with them is they are not very pretty with the stud & nut. That one might work OK if you could find some acorn cap nuts to hide the stud.

The one in the center I used to hold the outside chimney box for our wood stove about 40 years ago. They are still holding fine. The secret to the center one is to use the drill bit they recommend. They also look better with just the head showing.

[JHCC]

I was thinking that acorn nuts could be an option. 

[Frosty]

I've used anchors like the one on the left the most and the one on the right a few times and none have come loose as far as I know. I've used concrete anchor screws a couple times but not like the one shown, they were self drilling. No idea how they worked. My favorites were Epoxy anchor bolts, You predrilled the concrete to depth, inserted the glass tube of epoxy, catalyst and aggregate then put the bolt in the hole with the screw end double nutted and spun it with an impact wrench till it stalled. Do NOT let the driver hammer when it stops, it will break the bolt.

In the materials lab we used a lot of Cyl Cap a mixture of clay and sulfur but the stuff was intended to anchor bolts in concrete, masonry, stone, etc. Just melted sulfur works well for anchor bolts. It's very old school, think Rome.

Frosty The Lucky.

 

[JHCC]

Especially since sulfur has the unusual property of expanding as it cools from liquid to solid. 

[Frosty]

Ayup, funny stuff. 

Frosty The Lucky.

[BillyBones]

JHCC, if i were you i would go and ask the local building inspector. When i was building the porch on my house it had to be anchored to the foundation of the house. That center anchor was a definite no-go for that purpose. Ended up having to run bolts all the way through with a washer and nut on the backside. That was for a porch though and not railing. What i do know about concrete anchors is that the ones that are held in with an adhesive are about the strongest you can get. I also know that depending on if the anchors go in horizontally or vertical will make a  difference with the building code. 

A search for "Ohio building code concrete anchors" turned up a bunch of info. I did not go deep just a quick gander. Also local building code may differ from state code. 

[Stash]

John- what is the attachment point of your railings? How is it built? I've seen where the railing post is set into the mounting hole with non- shrinking grout. I've core drilled into stonework to do the same.

Steve

 

[Steve Sells]

I would avoid the tap-cons, they dont do as well where wriggling is involved.

[anvil]

I've always used Red Head wedge anchors. They are great quality. 

To be fancy, I normally make a hand forged washer, cut the excess threaded stud off, and make a decorative nut. I've even made special wrenches to work with the decorative nuts when needed.

 

Edit

Heres the tools I use to make cap,crown,acorn nuts.  The nut is forged to rough shape on the end of a 1" square bar. Then brought to a good yellow heat and upset in the tool to get its final shape and to make them all the same. After it cools, Cut it off to fit the die. Replace the lid and tighten it down. Now you can easily find the center of the nut. Center punch, leave the lid on and drill and tap. With the lid screwed on, the nut will stay put when clamped in your drill vice. 

I make the tool in reverse. Forge your cap nut on the end of the bar out of mild steel. Then heat the block to a good yellow and hammer the nut into it. Take as many heats as needed and keep the end cool and the block hot.  When done, make the lid and drill both pieces for the screw. done. Everything is mild steel and no heat treat needed. 

[anvil]

 Heres a pic of the nuts from the die above. I didn't do the install, but it is similar to your question, just in the vertical.  They used epoxy to secure the studs in the wall. I did this back in the late '80's and there were about 200' of hand rail. The railings are out of 1-1/2" square stock forged on the diamond.

[Latticino]

John,

From what I've seen of your railing design (great looking project BTW), there are some rather large potential lateral side forces on the relatively small weld joints to the pair of brackets you will be attaching to the concrete.  As the railing will be for Lisa's business there could be liability issues if something happens and there is a failure at the bracket connection (where the most potential torque will be).  Due to the configuration of the brackets much of the lateral "pull out" load will be taken up by the side scrolls, so I would expect almost all of the above choices for bolting will work if properly installed (particularly if you attach the side scroll on the bracket to the vertical rise of the stair).  I wouldn't expect the bolts to fail in shear if large enough ones are selected.  If you know a congenial structural engineer you may want to get their input before making a final decision.  I know it doesn't meet the current aesthetic, but in your shoes I would be considering a side brace to the adjacent column or porch landing.  It doesn't have to be massive, and can certainly match the scroll theme.  If nothing else, please ensure you have really excellent penetration when you finally finish weld the brackets in place.

[JHCC]

I’ll be putting in some deep bevels before welding, and my most recently purchased spool of FCAW wire has been giving me really good penetration. I’m also considering a heavy rivet in the middle  each of those joints, to add some mechanical strength. 

[Irondragon Forge ClayWorks]

59 minutes ago, Latticino said:

side brace to the adjacent column or porch landing. 

I also thought that brace would be prudent, it would greatly help in any lateral force being applied to the railing, as some folks are likely to do by pulling or pushing the railing. Other than that the railing is top notch and something to be proud of.