Extending a hearth

[Skier76]

We're going to be installing a pellet stove in our weekend house in Southern VT. The guy from the stove store came out to look things over. He recomended extending the hearth out about 6". The current set up is a homebrew made by the previous owners. It's basically poured cement, nothing fancy at all.

My thought was to just build a form about 6" away from the current hearth, mix some concrete, pour, done. But will I need anything to help the nex section "join" the old section? Maybe some cement lags/screws in the face of the current hearth so the new cement has something to grab on to?

Oh, this is located in the lower level of the house. Which is a on a poured concrete slab. So after removing the stylish fake wood (vinyal) around the hearth, it will be poured right on to concrete.

Thoughts?

 

[fossil]

I s'pose cementing some rebar or something into the existing edge wouldn't be a bad idea if you're just going to pour a concrete addition onto what's there. I've no idea how high this hearth is above the existing floor, but the other idea that occured to me was to set masonry pieces in mortar...standard bricks or non-standard bricks...which would serve the purpose of extending the hearth, while also "trimming it out". A pic of the existing location would certainly help. Rick

 

[Gooserider]

There is an article in the HearthWiki about making hearth extensions, but that was mostly focused on doing extensions over combustible flooring in ways that would meet code requirements. Doing an extension on a non-combustible floor will be much easier since R-values and such aren't really a concern, as long as you don't use combustible material in the extension...

I think your idea of putting some lags or rebar into the old hearth is a good one, I'd also make sure to rough up the cement you will be building the extension on as well, and possibly put a couple of lags in that as well - you need to bond to both the old hearth AND the original floor...

Gooserider

 

[dgold]

I like your idea of making a form and pouring the concrete into it, but personally, I don't think you're saving much time or energy by tying the new pour into the existing hearth. The right way would be to drill holes, blow-out the holes (to remove the dust), add a chemical anchor, and insert bolts / threaded rod / rebar, so that the new pour is tied to the existing one.

Personally, I think it'd be just as easy to break out the existing one, and make one monolithic pour inside your form. The bagged concrete's you buy at the boxes are super strong. If you use something like quickcrete, you probably don't even need any reinforcement. Concrete is cheap and relatively easy to work with.

Will you tile over it? If not, you need to make sure you get all the bubbles out along the form. Plenty of gentle tapping of the form with a mallet or hammer should help - be sure to spend a little extra time in the corners too. If you decide to tile over it, no worries, you'll just have extra surface area for your thinset to adhere to.

 

[Skier76]

Thanks guys! I'll get some pics up tonight hopefully. I've spent some time on the "stone" walls around the hearth. The previous owners never got around to cleaning up the cement "grout". So I got to spend some time with my drill, a few wire wheels and the vac. I can still taste the cement dust...blah!

I'm not exactly sure how they built this hearth pad. I'm going to assume (you know where that gets me!) that they just poured over the floor; using some simple 2x4 forms. The pad is only a few inches high. In fact, it's about as tall as a brick if you lay it on it's side.