making my own hearth extension pad?

[iamquaker]

so i need an extra 12" in front of my existing hearth to have my new insert pass code.

stopped by the local fireplace shop at lunch and for a 12" hearth extension pad was $220

i was thinking about either making my own pad? or cuting out the carpet for 12" and installing some ceramic floor tile in front of the existing hearth.

what have you all done to resolve these issues?

thanks

 

[Gooserider]

There is an extensive article I've been working on in the Hearth Wiki that addresses the entire subject of hearth pad design and construction. It is HERE! I would suggest that you start by reading the article, and then asking any questions you have left...

In short, building an extension is basically the same as building a complete hearth pad, the same principles apply. You need to determine the size (in this case of just the extension) and R-value requirements, then choose appropriate materials and design to fit the requirements. IMPORTANT NOTE - The Code reqirements spelled out in the NFPA 211 standards have just changed! You now must have at least 18 inches in front of your loading doors, not the 16" specified for the US in many manuals - make sure your design gives you this or you may have problems with your inspection.

I would verify that your existing hearth meets the R-value requirements for the stove you are planning to install, and build your extension to the same R-value as the existing hearth.

One thing I haven't put in the article yet, but need to, is that if you are building a split level hearth, the stove MUST be on the highest part of it - you can't build an extension that sticks up higher than the area the stove is sitting on. (It is OK if the extension is lower)

i was thinking about either making my own pad? or cuting out the carpet for 12” and installing some ceramic floor tile in front of the existing hearth.

I think cutting the carpet gives better results. Note that much depends on your installation, a low R-value stove, or one that just says "Non-combustible floor protection" will probably let you get away with just a layer of tiles instead of the carpet. If you need more than that, it is possible to also cut out a section of the sub-floor (and if really needed, with more difficulty) the decking under it, and build back up with some combination of insulating materials to reach or exceed the required R-value, and still come up with a flush installation. (See the above article for details)

A few other things that will help us give better advice...

What does the current setup look like? - Photos are helpful!
What is the R-value of the existing hearth?
Is the existing hearth flush with the floor, or raised? If raised, how high is it?
What kind of stove are you planning to install? What does the manual say it requires for R-Value on the floor protection?

Gooserider

 

[jqgs214]

I just completed a very similar project. I cut out my carpet, cut out the hardwood floor that was underneath that and built it back up fluch to the existing hearth level with cement board and then tiled over the whole thing. My stove called for a non-combustible hearth so I only used 2 layers of cementboard and then the tile which worked out pretty darn close to level.

 

[webbie]

If the hearth is raised (your fireplace hearth) more than a few inches, then chances are that spark protection is the order of the day as opposed to heat and R-values. There are ways you can solve this problem both with cutting out carpet and perhaps without doing so. If the protection is just for sparks, I have had folks find a decent piece of slate or blue stone and set it down in front of the hearth. In such a case, it is a good idea to slip a small piece o sheet metal against the hearth and then under some of the stone, just to prevent a stray spark from going down there. You could also make up a rigid, but removable mini-stove board using 2 thicknesses or so of Cement Board with tile over it. The tough thing with that, is that if you constantly step on it and "rock" it, it is likely to crack.

A stone fabricator can also cut you a piece of countertop granite or related material for the same use.

Lastly, Heat Safe used to make a UL approved hearth extension piece that must be less than $75. I can't find them on the net right now, but they were 16 or 18" x 48" and very lightweight. The safest installation of such a board would be to screw it down to the subfloor in such a way that it cannot be kicked out of the way.

Personally, I'd either cut the carpet and use tile (and cement board if R-factor is needed), or go with the heavier stone thingy, which could probably be done either with cutting or without.

Here is a link to a distribution that sells some units that are as low as $60.....
http://tinyurl.com/yo3da7

Your dealer may be able to order there also.

 

[Gooserider]

Certainly this seems to be the season for hearth design and building... Glad I got the Wiki article started when I did, there's more I'd like to do with it, but most will probably wait till after the party.

Webmaster: If the hearth is raised (your fireplace hearth) more than a few inches, then chances are that spark protection is the order of the day as opposed to heat and R-values.

I agree with you in the theory on this Craig, but do you have any hard numbers that would quantify it better? It would be nice, because it would make hearth pad design a great deal easier for many folks (myself among them) I have seen discussion of doing "split level" hearths in the Hearthstone Homestead manual that backs you up, but they didn't really give more than measurement ranges.

Assume that you are having to deal with an inspector that's as hard-core as Elk, but doesn't have Elk's experience w/ stoves and such. He opens the manual for the stove and sees that you need an R-value of some high number - lets say 2.0 for discussion's sake. The manual doesn't mention split level hearths at all. You built a split level that was 9" high under the stove, with an R-value of 4.5+ (18 layers of Durock, plus tile) and an 18" extension of ceramic tile over plywood in front of it. (Note that this would EXCEED the listed requirements for the 6" leg Hearthstone Homestead, but our hypothetical stove manual doesn't talk about split level hearths) What "authoritative source" would you point the inspector at in order to convince him that your hearth extension is compliant?

IOW, what is the "R-Value" of an inch of open air space, w/o shielding, or other protection, but in addition to the leg height of the stove...

I've trotted this picture out before, but I think it gives the idea - what is the "R-value" (or equivalent term that can be used the same way) of the space over the lower level???

 

[Tendencies]

I did the carpet cut out, then replaced it with durarock and ceramic tile with a nice oak trim, came out great and I only had about $50 in the whole thing.

T

 

[webbie]

There are a lot of ways you could qualify the distance required, but in an inspection situation you always have to present these to the official for his perusal. Here are a couple of what might be guidelines:

1. NFPA clearly addresses the hearth requirements based on the leg height. Well, it would seem that hearth height would function in the same way.

2. Some stoves, such as the HearthStone we mentioned earlier, actually have published the specs for the "spark guard" part of the hearth.

3. Premade stoveboards, made for this purpose and approved start at $59 and go up from there. They are typically a piece of micore-like material, with one sheet of sheet meal over them. Of course, these are also approved for flush hearths, so they probably have a relatively high R-Value.

Each manufacturer decides how few or how many situations they are going to test to. That is why NFPA as well as common sense and experience (and other codes) enter into the equation. It seems simple - follow the book - but as we can see here it is often a combination of many books!

A good real world example is the HearthStone Homestead, which addresses a lot of these point in their manual. In this case, then the hearth is raised 9" or more, no R-Value (just non-combustible) is required. When the hearth is only raised 2". the R-value is still reduced from that needed under the stove (by about 60%)

This is almost a worse-case stove, since it sits on mini-legs, sits out near the end of the hearth (stove and glass can radiate down easier), etc.

See enclosed or go to HearthStone site.

An important point becomes which brand and model is installed, and how far out does it protrude now compared to the hearth length.

 

[chevyhd]

I made an extension for my hearth also. I used cement board cut to the length of my existing hearth and tiled that, then just uhsed 1/4 round for trim. It measures about 6 feet long by 1.5 feet wide. I just lay it on top of the carpet since I have a raised hearth. It only cost about $30 and can be moved when the burnong season is over, but it is heavy. If you use 1/2" cement board and tile it comes out to about 5/8" thick, which is perfect for using 1/4 round trim since it comes in 5/8" also..

 

[dmt5000]

I am working on an installation where the stove is sitting on a manufactured hearth pad in front of an 8" high raised fireplace hearth (rather than on top of the hearth). The stove manual calls for an 11" clearance from the rear of the stove (which has a rear heat sheild) to a protected surface. Assuming the raised hearth, which is brick, is constructed over timber framing and therefore needs protection, what kind of configuration should a metal shield take in this type of installation, i. e., where the stove extends above the top of the hearth. There are clear guidelines for shield height on a wall behind the stove, but not this case, where there is essentially an 8" high wall behind the stove. Any help is appreciated.

 

[Gooserider]

I am working on an installation where the stove is sitting on a manufactured hearth pad in front of an 8" high raised fireplace hearth (rather than on top of the hearth). The stove manual calls for an 11" clearance from the rear of the stove (which has a rear heat sheild) to a protected surface. Assuming the raised hearth, which is brick, is constructed over timber framing and therefore needs protection, what kind of configuration should a metal shield take in this type of installation, i. e., where the stove extends above the top of the hearth. There are clear guidelines for shield height on a wall behind the stove, but not this case, where there is essentially an 8" high wall behind the stove. Any help is appreciated.

I'm not sure I totally understand the question, perhaps a photo or a rough sketch might help. :-S

However unless you have definite reason to think otherwise, I'd strongly be inclined to think a raised hearth would be made from 100% non-combustibles, (or at least the raised part - it may be sitting on a wooden floor...)

If the 8" wall is non-combustible then it essentially doesn't count for clearance purposes, and becomes a non-issue. You'd want a couple inches to ensure air circulation around the stove, but no problem beyond that.

If you do know the 8" wall IS combustible, my 100% pure, non-official, gut instinct feeling (it clear that this is a guess? :lol: ) is that you would need to do an NFPA clearance reduction shield up the 8" and then back to the 11" depth, which would be kind of strange looking. I'd be more inclined to get rid of the raised hearth if possible, or consider boosting the stove up to be flush with the raised hearth...

Gooserider