New bluestone hearth - meet requirements?

[Old20sHome1985]

Hello All,

Thank you for the previous help with everything regarding my clearance to combustibles and hearth construction. To recap, I am having a new Avalon Olympic installed (next monday) and am finishing up the final hearth construction to which it will be sitting on.

I chipped off all of the old red tile. The concrete base below was pitched to match the wood floor, which is unlevel and pitched. So I had my father assist me in using rapidset to bring the concrete up to be level all the way around. I now have a nice level base to be able to sit my new piece of Bluestone slab on for my new hearth.

Clearance requirements for the Olympic is 16" in front of the glass. Given the stove will stick out 8.5", the hearth would need to be about 25" deep in total. Due to the existing size of the concrete pad, I could only get away with a 22" deep piece of bluestone without cutting the floor and subfloor and pouring a larger concrete base. The plan was to then cut out the wood floor, and use a durock base and some nice tile inset into the floor, since the stove only requires ember protection (Must be non-combustible and at least .018" thick (26 gauge) )

However things have changed. I sustained an injury that has been plaguing me for over 3 months now and has taken its toll to the point where i cannot do any great amounts of physical labor. (pinched nerve causing loss of use and feeling in right arm and legs) So I am forced to finish up this hearth job a little quicker in order to still allow for the stove to be installed on Monday.

First, the concrete base we leveled out ended up having some slight low spots here and there, nothing major. Corner to corner, the concrete base is level, however in between there may be an 1/8" low spot here and there. Can I mix a small batch of thinset (versabond fortified) and use this to fill in the small low spots to create a more uniform pad before installing the bluestone hearth? Lowspots would be filled today, pad installed tomorrow or Friday. Or when I install the bluestone and use a 1/4" trowel, will this be enough to fill in the low spots?

Second. I do not have the strength or time now to cut the wood floor out, lay the durock and tile to create the full 16" clearance in front of the stove. Realistically, the bluestone hearth pad provides 13" of clearance, so I am short by 3". For now, I ordered a HY-C Type II Hearth Extender from woodland direct to make up for the difference.

http://www.woodlanddirect.com/Wood-...ns/HY-C-Black-Type-2-Hearth-Extension-18-x-48

With this in front of the bluestone on the floor, I should fulfill my requirements per the stove mfg. Am I correct or am I missing something?

I have attached some pics of my current fire place and the progress. First pic is the original tile and tape marking out area of original construction.

Second pic is the concrete below the original tile and the terrible pitch.

Third pic is the concrete poured to level for the new pad.

Fourth pic is a test fit of the pad before the concrete was poured.

Thanks for the help everyone. I plan to have this pad installed by Friday so it can set and be ready for the stove install on Monday. Then some trimwork, and the inspection and ready for winter. I do plan on doing the tile extension at some point, but it is impossible right now.

 

[mstoelton]

Too bad you didn't order the bluestone a few inches longer. You could have cantilevered the stone out several inches and then put supports (think 1/4 inch thick, 2 inch wide steel straps) under the bluestaone. I did this with my soapstone hearth and it turned out great. The soapstone hearth is cantilevered 5 inches past the underlying brick hearth base.

I used fortified stone setting thinset to set the soapstone hearth and used a 1/4 inch steel strap every 1.5 feet to support the cantilever. I drilled holes in the straps and tapconned the straps to the underlying hearth before the stone was set. The supports worked out great and provided a "spacer" to prevent the heavy hearthstone from squishing out all of the thinset.

And yes, you are fine with using fortified thinset to smooth the irregularities. You will need to give the thinset time to dry.

Based on what I see in your pics, it looks like you might find that you need to raise the floor of your firebox a bit to match the level of the bluestone if you are having a stove installed that crosses the opening. you could do this with cement board and tile or an additional piece of stone.

 

[Nick Mystic]

Was this piece of bluestone already cut when you bought it? The reason I ask is because in your photo it looks like the stone extends an inch or so beyond the fireplace on each side. Did you want it to extend out like that for a reason? Also, I'm wondering why you didn't pour your new concrete slab so that it would match up with the height of the floor. The stone looks a bit odd to me sitting up in the air with that gap showing all around its edge. Are you going to build some sort of frame around the stone or will you leave this gap exposed? Finally, is there a basement or crawlspace under this area? If so, have you inspected down there to see if it looks substantial enough to carry all this extra load you are going to place on it? By the time you add up the weight of the concrete, bluestone, and new stove you could be pushing a 1000 lbs. or more. Good Luck with the rest of your installation.

As mstoelton mentioned, you will almost certainly need to do something inside the fireplace to bring the floor up to the same height as the new hearth. Since part of the insert is extending out onto the heart the rear of the insert will need to be up to the same level.

 

[Old20sHome1985]

mstoelton:
The reason we did not order it longer was because we did not want it to extend much farther into the room. With the way the room is situated, there is a walking path that goes by the hearth. If we extended it out another 4+ inches, it would have been a tripping hazard. I had thought of this option. But we opted to keep the hearth back around the original concrete depth, and then extend the protection with inset tile into the floor. This way the inset tile would not be a hazard. But best laid plans go to hell when you get hurt and now I am scrambling to finish this so I can get the stove installed and still pass inspection.

If I used the thinset tonight, would I be able to install the bluestone tomorrow or have to wait longer?

And yes, I do need to bring up the firebox. I am going to use 1-1/2" thick concrete block and just place them in the void. Since the block below is mortared in, then I will just set them in and cut to shape to make up for the difference. It does not have to be perfect however since the stove has adjustment legs that can adjust up to 2 inches. the stove installer told me if i wanted to bring the box up, I could but the legs can make up the difference.

Nick Mystic:
I bought it with an overhang. When everything is said and done, there will be an equal 1-1/2" overhang around the entire pad. I have stained wood trim that will trim below the pad and on the floor to finish it off nicely. I did want it to extend out, but just a little bit. I looked at a couple of options and liked the overhang. Again, I will be doing trim work when everything is said and done to finish it nicely. The pic you see with the bluestone is it just sitting on shims, no concrete because it had not been leveled yet, so the rest looks a bit wierd.

If I had poured a new concrete slab to try and match the height of the floor, I would have had to demo the existing concrete down to the lathe below, reform and repour. However this would have still created a problem because the floor is over an inch higher on one side of the hearth then the other. It is the way the house settled. So the hearth would have been flush one side, and then sticking above the floor on the other side. So I opted to bring the concrete pad to the height of the firebox floor, so the new bluestone would just sit above that. Yes it adds weight, but I removed easily 80-100lbs of thick tile, used 80lbs on concrete to bring the level up, and then am just adding the bluestone so I think I will be ok.

 

[Old20sHome1985]

Everything said and done though, with the hearth and the type II pad, I assume I meet my requirements?

 

[begreen]

Yes, that should meet the requirements and be fine. Sorry to hear about the injury. Hope that gets better over time.

 

[Old20sHome1985]

Thank you. I have nerve conduction testing Friday and we will see from there. Have muscle loss in right shoulder and arm due to the nerve damage and tingling in fingers. Feet are numb up to my lower back too. This on top of the pain. Gotta love it.

 

[mstoelton]

I would not try to level with the thinset at this time. I would set the bluestone using shims and level the bluestone with thinset when you do the bluestone installation. Add some extra thinset and then let is squeeze out and make it level to your satisfaction that way.

 

[Old20sHome1985]

Perfect. Sounds good to me. Like I said there are small lows, but nothing drastic. I figured I could make it up when I set the bluestone but wanted to get some input.