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Building hearth extension for insert

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Dunadan, Sep 21, 2007.

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  1. Dunadan

    Dunadan New Member

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    I'm thinking about building my own hearth extension for my Revere insert.

    I've searched the forums and read most of the posts about hearth extensions, as well as the Wiki article on Hearth Design. I also checked my manual for hearth requirements, and all it says is that it must extend 16" (I understand now 18") beyond insert and be non-combustible and at least .018" thick (26 gauge).

    Does this mean I don't need to worry about R-values and that the hearth is mainly for spark (log roll-out) protection?

    If so, can I just use plywood topped with ceramic tile? Or can you not put tile directly on plywood and need a cement board as a basic foundation (not for insulation purposes). Sorry to sound like a newb, but when it comes to tile I am. Any suggestions on the easiest way to go about this would be great.

    Looking to make my extension about 18" x 48". Nothing fancy - just want to stop having to use my 2 giant pieces of slate. I'd like to trim it with some nice wood trim, so my thickness needs to work out with this in mind.

    Thanks!

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  2. nshif

    nshif New Member

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    Well if nobodys gonna answer this Ill give it a shot;
    Id get a piece of 26ga sheet metal and put that directly on the sub floor
    Then Id put a 1/2" layer of cement board and then tile.
    Id use cement board because youll get better adhesion to the tile then with plywood plus its non combustable, if you drop a log on it and its on plywood your probably going to get a crack, less likely with the cement board.
  3. Dunadan

    Dunadan New Member

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    Sorry...need to clarify, though I think most of the points above would still apply.

    This would be an pad type extension that lays directly over a hardwood floor (or carpet at some point if we decide to put in carpet. I'm not looking (yet) to put in anything permanent.
  4. nshif

    nshif New Member

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    If its too flexable underneth the tile is gonna crack. I wouldnt put carpert under it.But it doesnt have to be attached, its gonna weigh enough that its not gonna go anywhere. Id attach the metal to the cement with some suitable adhesive.
  5. Rhone

    Rhone Minister of Fire

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    Yup. Most specifiy that the hearth needs to have an R-Value, yours doesn't so you don't need to insulate it. In fact, yours goes a step further and specifies a piece of 26 gauge metal is sufficient protection! Wow. Of course, can't hurt to go more. As for the 18", your manual says you need a 26" hearth from the face of the fireplace. Since your unit sticks out 10" that's 16" more in front of the loading door, which is common. Canada requires 18".

    You don't usually want to put tile on plywood if you can help it, the worst thing for tile is a floor that moves. Tiles hate vibrations, and expansion/contraction can cause the bonds between the tiles/grout/mortar to fail and you get things like tiles that pop or come loose. It's particularly bad near an insert as, the heat will dry out the wood tremendously in winter causing a massive shrinkage, and in summer the humidity rises causing the wood to exand. Fortunately plywood does it to a lesser extent than other types. If you're still inclinded to use plywood the normal procedure is to coat it with a layer of underlayment (pick some up at your local hardware store) which is specifically made to bond to wood. It's rather similar to cement, you put just a thin coat of it on. Once it dries, then bond your tile to the underlayment but to avoid the hassles of possibly popping tiles use cement board if at all possible plus, it's added protection as it's not combustible.
  6. Rhone

    Rhone Minister of Fire

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    I type too slow.

    I think the slate probably the best thing going that being the case. I don't believe tiles will stay on a thing you move around.
  7. titan

    titan Minister of Fire

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    Dunadan, check out "Hearthpads.com" if your looking for a wood-trimmed hearth extension to sit on your existing floor.I'm not trying to sell them,but they might be a simple fix if you decide against building one.Btw will someone please school me on how to post links to websites?
  8. Dunadan

    Dunadan New Member

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    Titan - I've seen those and that's what I have in mind, but I was thinking I could build my own for a lot cheaper than $169/$189 and have a bit more control over what I get.

    Rhonemas - The problem with the slate is it's not all that great looking and I need 2 slabs to provide the width I need, so it's doubly not great looking.

    You really don't think I could make a moveable pad that wouldn't hold together? Actually, I probably won't be moving it all that much going forward, as my son is just about ready to walk. I'll probably be leaving up the Hearth Gate to protect him whether it's burn season or not, so I could really leave the pad in place.

    Eventually I want to rebuild my hearth, but that's a next year project.
  9. nshif

    nshif New Member

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    If you dont need to move it much then what I suggested will work but if you do its gonna be heavy and a pain and may not be solid enuf.
  10. Rhone

    Rhone Minister of Fire

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    You could do it, I personally would use a piece of cement board (heavy!) but you can try the plywood with underlayment. It's not like you'll break the bank, it will certainly last the first year and, even if you pop a tile in the future look on the web about how to repair it, you just chip away the crap underneath and around, then goop it back up and put back. If you don't move it, will last years.
  11. Dunadan

    Dunadan New Member

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    Any plywood in that nshif? Also, why the metal? The tile and cement board should be overkill from a combustibility perspective.
  12. nshif

    nshif New Member

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    No no plywood. I just put in the metal because that was what your manual called out. I didnt plan on the cement board as fire protection ( which it is ) but as a better tile backer.
  13. Gooserider

    Gooserider Mod Emeritus

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    What is the floor under the proposed hearth? Carpet or something solid like wood or linoleum? Carpet may be problematic due to it's being "squishy" but a solid floor, I'd get a peice of Durock cement board and glue tiles to that. Thin carpet might not be that big of a problem, but the stuff that you go in up to your ankles in would be...

    I'm currently in the process of building in an extension to our hearth, in preparation for the VC Encore Cat that will be going on it. The existing raised brick hearth was designed for a side-load only stove, so it isn't deep enough for a front loader.

    I wanted the extension to be flush with the existing carpeted floor, so what I'm doing is removing a strip of carpet and the pad, then taking up the 1/2" particle board underlayment that was there, but leaving the subfloor decking in place. I am replacing the particle board with a layer of aluminum flashing (on general principles) followed by a layer of 1/2" Durock, which I'll be topping with 1/4" natural slate tiles.

    I've been going through all sorts of interesting times on the tech support lines to some of the various supply companies, and have discovered that all cement boards are definitely NOT alike. I will be updating the Hearth Wiki article shortly to incorporate my findings. One of which is that Durock seems to be the only brand that goes out of their way to specifically state their suitability for use in hearth construction. They also suggest using a "Latex fortified" thinset mortar to glue the tiles down with - Flexbond is the one that I will be using, which claims higher than average strength and resistance to flex and tile popping.

    Gooserider
  14. Dunadan

    Dunadan New Member

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    Currently I have a raised hearth (some type of hearth stone over brick) that sticks out about 9". In front of the hearth is hardwood floor, so what I was originally looking to do is lay a pad over the hardwood. At some in the near future we want to carpet the entire living room, so I want to keep that in mind while planning.

    I am now leaning towards installing the tile directly into the floor. This insert is never coming out - unless it gets replaced with another because the damper and part of flue were cut out to make room for liner. So... I figure why not do something permanent for protection.

    I'm assuming I have some type of sub-floor - since I have drop ceilings in basement I think it will be easy to determine this. My only concern now is how exactly to go about cutting out the hardwood. Obviously if I screw up, it's permanent. If I can determine how thick the hardwood is (not sure how to do this) I could use a circular saw to cut just that deep into the hardwood, and then cut out the rectangular area where the extension will go? Only problem would be cutting to the right depth and making sure my cuts are straight.

    Has anyone done this with hardwood? Any tips?
  15. Gooserider

    Gooserider Mod Emeritus

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    I'd lift one of the drop ceiling tiles to see just what you have, but I would expect that you will have some sort of subfloor decking, then maybe a subfloor of particle board or other sheet goods, followed by the visible flooring.

    I just did it with a carpeted floor, which made life a bit trickier, but essentially I did just what you suggested, set a circular saw to a bit over the depth of the particle board subfloor plus the carpet, and cut the line. Use a cheap carbide blade - you may find a nail or two, so you want a blade that is capable of dealing with nails, but not one you'll cry over if it gets messed up. Don't panic about minor grooves in the deck boards, they won't hurt anything. I used a 1" wood chisel to finish the ends of the cuts where I couldn't get with the saw.

    (I also found the circ saw did a great job of trimming the carpet. I cut out the strip of carpet I was removing first with a utility knife and pulled it out - If I was doing it over, I'd just have gone with the saw from the start...)

    Minor variations in the line (less than ~ 1/4") probably won't show / or can be hidden with the grout and whatever threshold treatment you use. I also found there is a bit of a challenge in fitting the cement board in that your raised hearth may not be perfectly straight, and you will need to do a bit of fitting on that side to get the clearance, or cut some extra space and plan to fill the gaps w/ thinset.

    Pick your extension dimensions based on tile units so that you don't have to cut tiles (include allowances for the grout lines) - this reduces hassles and saves work, also it will likely look better

    All cement board type products are NOT alike! Durock specifically lists use in hearths and clearance reduction walls as valid apps in their technical documentation, none of the other brands seem to, and I got mixed answers when calling the various tech support lines ranging from not reccomended (Wonderboard) to non-combustible only (Hardibacker) to "NOT non-combustible" (PermaBase) At this point, the only cement board product I would feel 100% comfortable with in using for a hearth extension is Durock. (I would probably consider Wonderboard or Hardibacker for clearance reduction)

    Gooserider
  16. Dunadan

    Dunadan New Member

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    Thanks Goose. Just got back from Home Depot to check out their tile and cement board options (Wonderboard and Hardibacker). I already plan to let the space be determined by my tile. If I can avoid cutting tile, I plan to do so.

    Concerning my cement board choice - since my insert only calls for .018" thick non-combustible surface, and tile/natural rock will be thicker than this, I'm thinking I don't need to use a board that is stated to be suitable for hearth situations. The only real need for this is to ensure I have a good base to secure the tile/stone too. Am I correct? If so, I would think my choice should be made based on what will be the easiest product to work with. From what I saw at HD, it looks like the Hardibacker would be easier to use, and less prone to crumble/break while transporting and cutting. Maybe I'm wrong?

    The only other catch right now is I don't have carpet in this room. Should I try to build the extension to be level with my current wood floor? The down side is after adding carpet, it might not be level with it. On the other hand, if I want to build it higher to try to match the carpet, I can't really do that until I know how thick my carpet will be, which I won't know until I actually go look for it. Of course, if I don't get around to putting the carpet in, or the wife changes her mind about it, then I'm not level with my floor. Sigh.
  17. Gooserider

    Gooserider Mod Emeritus

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    It's a mixed bag. Hardie didn't give me great feelings when I called their tech support line. I think it would work, given the "non-combustible" spec but I'd feel more comfortable w/ Durock (BTW, Lowes does carry Durock) Remember that tile gives nearly zero thermal protection, and Hardie seems lower than most cement boards. You don't require the thermal barrier, but I know that I'd feel better with it. I also know that my local FD guy said that he would like to see a reference saying the product was approved for the application - With Durock I can print it right off the web.

    I also put a layer of aluminum flashing under the Durock on my extension - maybe not needed but cheap "overkill"

    When you go for the adhesive, I would suggest getting "Flexbond" Latex Fortified Thinset Mortar - Durock says they want something that meets ANSI 118.1 and 118.4, and reccomends Latex Fortified - Flexbond meets both specs. The pre-mix "Omni-Grip" does not.

    In terms of how you build - is the current hardwood floor "real" or is it a laminate? If you carpet will you be pulling up the floor, or going over it? Depending on what you pick for carpeting, you may only be talking 1/2 to 3/4" difference, and can "fix" that with the way you do the edge treatment. I would say that your best bet would be to build for what you have now, flush to half the tile thickness above flush. Worst case you might have to put a second layer of tile over it later when you do the carpet.

    Gooserider
  18. Dunadan

    Dunadan New Member

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    I'll check out Lowes. I hate shopping there, as they only feel the need to have 1 register open (2 if it's rush hour) at any one time. Home Depot on the other hand always has people ready to check you out, as well as self-check out. But, I'll take a peak since I wasn't happy with the tile/stone at HD. You're right, if you can get the extra protection and peace of mind, might as well have it.

    This is real hardwood, not laminate. Can you tile over tile/rock without a problem? I would have thought you wouldn't have a good flat surface doing this.
  19. jqgs214

    jqgs214 Minister of Fire

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    Here is a pick of what I did, but I cut my rug and hardwood floor to fit 2 layers of 1/2" durorock and trimmed it out in oak. Its really and easy job, probably just as easy as doing a temp pad. then if you carpet you can just pull up the trim board, carpet to the tile and lay the trim back down.

    http://www.hearth.com/econtent/index.php/forums/viewthread/8388/
  20. Dunadan

    Dunadan New Member

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    Thanks wxman.

    I like that look.

    Any tips on cutting into the hardwood?
  21. jqgs214

    jqgs214 Minister of Fire

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    drop cut with a circular saw and chiseled the corners square. If you go a liitle too far the trim will cover it. or else your chiseling through about 1/2 a board.
  22. Gooserider

    Gooserider Mod Emeritus

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    I haven't had that much trouble w/ checkout at Lowes, although I don't shop there very often (HD is more convenient) - Minor giggle about the self checkout @ HD - A few weeks ago some guy apparently got upset going through the self checkout at an HD, and started whaling on the machine with the crowbar it was giving him a hard time about purchasing - Did about $10K worth of damage to the machine, dropped the crowbar and walked out. They are still looking for him. The host on the show had some advice for him if caught - Insist on a Jury Trial, nobody who has ever used one of those self checkouts will vote to convict... :lol:

    Now if I use one of the people checkouts @ HD, I apologize and explain that I didn't want to use the self checkout since I wasn't purchasing a crowbar....

    Gooserider
  23. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    As Paul Harvey used to say: "Now on page two".

    The guy got upset when he accidentally hit the button for Spanish instead of English. When he couldn't understand the machine he put the pry bar through the screen.
  24. titan

    titan Minister of Fire

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    So he tested the crowbar on the self-checkout machine,wasn't happy with its'performance, and changed his mind about buying it.--Sounds logical....
  25. Dunadan

    Dunadan New Member

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    Well determining the thickness of my floor components isn't going to be all that easy. I tried to check along the edges of some of the rooms, but they are either covered by baseboard heat, or multiple moldings.

    I checked in the drop ceiling of the basement, and I can see a layer of plywood (the sub-floor?) above the joists (2x10s). I see no planking, but between the joists running down the middle of the floor are some wood cross braces. If there was planking, I'm guessing I would see it looking up through the drop ceiling? I did notice that right underneath what I assume is either the actual firebox or hearth there is a triple 2x10 joist.

    The only way I can get any indication of the thickness of the sub-floor vs. hardwood is by measuring the holes I've drilled through the floor to run electronic/computer cables. The thickness of the entire floor looks to be 1.5". Peaking into these holes as best I can with a flashlight, the sub-floor looks to be about 1/2", which would put the hardwood at about 3/4". Does this sound right?

    I can just hear my wife if I wind up ruining the hardwood and sub-floor by calculating wrong :bug:
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