Update on Fireplace Refacing Build

[midfiman]

Hello everyone.

I wanted to provide a follow up since I came here seeking info (and good answers, thank you) before starting my fireplace remodeling task. As you probably (don't) recall, I had an old 80s untreated brick fireplace that my wife and I wanted to redo to have a natural stone finish. We looked at the veneer stone but between the labor and the cost of the stone, it was getting quite pricey. My mason friend was able to get a very good deal on natural stone that he cut into 2-2.5" thick stones and said he can do it for very cheap labor. This is the route we went. So we broke the brick on the hearth and put down a piece of (very heavy) 2" thick blue mist granite, and then started building on top of that.

He is using a mixture of Type S Mason Mix with Portland cement, and putting in the Quikrete Bonding Adhesive as he said that will really make the bonding strength super strong. We are using a drystack method, stacking the stones on top of each other, the first half, directly attached to the strong and untreated bricks, the top half to a build out box (studs and plywood, very securely attached to the wall with GRK structural screws), covered in Tyvek (to slow down the absorbtion of the water from the cement), then covered in 2.5lb metal lath, attached on the studs every 6", but then additional screws put in between in the plywood (not sure these themselves will do all that much). We also put in 5/16" eyehole bolts through the lath, plywood and directly in to the studs behind. We figured these were much stronger than basic wall ties when embedded into the cement. I've put them in ever 16" or so up the 4 stud lines, but plan on putting more per my mason. He said they can't hurt and he loves the idea as these are rock solid in the studs. Lastly, you'll notice in the picture (maybe) 4 large bolts that were attached to the studs behind the plywood with nuts and stick out to provide a place to mount the header stud for a mantel shelf that will be done when (if) we finish the stone work...

To solve the issue of over the firebox opening, we installed a 3"x3" 1/4 thick metal angle to transfer the weight on top of it to the two sides. The metal fabricator seems to think this piece of metal is super strong and will be more than enough to support that weight, though the wall will help with that.

So, this is a ton of weight (more actually, mason estimates upwards of maybe 3,500 lbs), so we've beefed up in the basement with 2 rows of double 2x10s, directly under the hearth extension, supported by 3 PT4x4 (so spacing is only 3 ft between supports). One of these rows lines up directly below the new stone "walls".

I am, by nature, a worry wart. So a few things that worry me.

Is the support I built below strong enough? I've looked up some crazy numbers on how much weight a 2x10 can support when supports are like 12' apart and the number is pretty large. These are doubled, two rows of it, and supports very close. It seems that a 4x4 vertically can also support an crazy amount of weight. I think this is overbuilt, but I'm curious.

How much of the weight here is being supported by the wall vs going straight down. I would imagine no matter how strong the adhension is, the sheer weight of the stones would make the force of weight go downwards and the wall isn't doing much.

Is the Type S, Portland, Bonding Adhesive a good way to go? The mason claims this bond will be super strong, and me playing with a few stones a day after seem to indicate they are stuck to the brick like solid concrete, but just wondering (I undertand proportions make a difference). That being said, he said a little "glue" goes a long way, as what you see in the pictures below, he's only used like 2/3 gallon of it so far...

For the lath, we have attached the heck out of it to the plywood (through to the studs of course) and then my mason said instead of a scratch coat, he prefers to do a wet coat over the lath right before doing a row and then putting on 3-4 inches of cement on the back of the stone and pressing it into the lath and then chopping/pressing behind the stone to really get it pressed in good. He says this actually creates a much stronger bond because you're not attaching it to a dry layer even if its textured/wet down before applying. Does this sound right?

I just want to make sure I don't have stones falling from 9' up as these are not exactly light 3/4" air stones, etc. I think we are doing all we can to make this go well, but would love to hear if you see any points of failure here that we're not accounting for. I'm all about overdoing it, but this is out of my area of exertise by a long shot.

Thanks for your time, and sorry for the long post.

Regards,
Midfi

 

[bholler]

So are you actually dry stacking with no bedding mortar at all?

 

[midfiman]

I'm not sure I understand (not sure what bedding mortar is)... ...there is between 1 to 2" of mortar behind all of the stones which attach it to the substrate behind it. There is some mortar between the stones as well, though not a lot. Its all about the stones mostly resting on each other, with their backs attached to the wall.

Is this not right?

 

[midfiman]

Should he be adding mortar between the stones to make it stronger (there is some, just not a lot as he says the idea of drystacking is for the weight to be transferred from stone to stone, with them being held in place with the large amounts of mortar on their back.

Sorry, this is out of my league, hence looking for feedback. Thanks!

 

[moresnow]

Look familiar? Sitting in a wainting room at our local hospital. This "dry stacked" arrangement surrounds a Heat N Glo unit. We call this style of stone work Lick and Stick locally. Zero structural responsibility in the applications I've been around. Aesthetics only. This wall has horizontal waves in it from the installer starting on the un uniform floor! Duh. Fwiw