Hearth Screw up

[Harvey]

Hi -

I built a hearth (5'x5') for my Englander 13-NC (leg model) using 2 layers of 1/2" Durock and 3/8" porcelain tile.

It looks great, but my R value is only .53 instead of the 2.0 stated in the owners manual.

I haven't installed the stove yet and I was thinking of building a platform of 1/2" Durock -> 2" thick concrete pavers -> 1/2" Durock -> 3/8" tile -- for under the stove and leave the rest of the hearth as is.

Will this be sufficient or should I rip it out and start over?

Thanks for any ideas or help.

 

[edthedawg]

Sounds like you may need to do a tear-out or a bigger build-over.

Your original build is about R 0.43, according to http://www.chimneysweeponline.com/horvalue.htm and that jives with the values Hearthstone publishes, too (I'm not an Englander authority and I don't play one on tv).

Your proposed extension gets you to about R 1.05 (see screencap attached). Still far short of your R 2.0 requirement. You could probably get there by adding a grid of steel studs (horizontal dead air space provides about R 0.9 per inch, I believe) or simply more layers of 1/2" durock if you think the house won't have an issue supporting the extra weight.

It's also concerning that you propose (and pls correct me if I'm misinterpreting your words) just building a platform underneath the stove? Your hearth should provide the specified R-value protection over the entire minimum footprint of the hearth, as determined by your specific clearances to combustibles, and ember protection requirements all around the stove itself.

In other words, if your manual says you need R 2.0 protection extending 16" to the front, left, right, and back, and your stove has a 15x30 footprint, then (barring combustible wall clearance issues) you need a hearth that's about 62" wide (16+16+30) and 47" deep (16+16+15). You can build the hearth bigger if you want, but you must provide the R 2.0 protection over that 62x47 minimum area centered under the stove.

Hope this helps. I wound up spending back to back weekends building over a really nice hearth myself... sorry to hear you're in the same boat.

 

[G-rott]

Look into Micore or a similar product to make a section of raised hearth for your stove. If you use steel studs to create a platform a few inches high it can actually make loading the stove easier. Plan you dimensions based on the size of the tile you are going to cover it with.

Garett

 

[Harvey]

Thanks for the ideas. I like the idea of building up the hearth under the stove. If I use 8x8x16 CMU's, Durock and tile, the extra height under the stove will look good and it will give me a project for the weekend.