Durock strips in hearth

[rsiros]

Started the hearth project, and I'm trying to create a one inch space for some insulation to lay in. I would like to know the best way to make this "cavity". I have read numerous posts about using metal studs, but I have an extra sheet of Durock that I could cut into strips. Any thoughts and/or experiences?

 

[Hogwildz]

I don't see why not. It isn't combustible. What are you putting on top of the Durock strips? More Durock?

 

[begreen]

That should work fine. Just follow the same support spacing that you would if they were metal studs. I like 12" spacings for doubled durock on the hearth.

 

[rsiros]

I will be putting Durock over the strips. My biggest concern was the structural integrity once it was cut into strips and had a lot of weight on it. I've only used it in sheets.

 

[SlyFerret]

That should work fine. Just follow the same support spacing that you would if they were metal studs. I like 12" spacings for doubled durock on the hearth.

I'm using metal studs on my hearth, but I'm going with about 6" spacing on centers. Should be good and solid. Similar construction to what you're doing.

-SF

 

[Hogwildz]

I will be putting Durock over the strips. My biggest concern was the structural integrity once it was cut into strips and had a lot of weight on it. I've only used it in sheets.

You should be fine. I myself would make 6" strips and center then around 12" as Begreen suggested. So your filling in 6" of space between and now have a 6" pocket between each. That should be more than enough support for the Durock sheet(s) over top. Better overkill and sturdy, then under done and weak. Don't forget to use the Durock or equivalent fastener made for cement board.

 

[rsiros]

Thanks! What's the best way to cut it? I've used my circular saw in the past with a carbide blade for clean cuts, but I don't want to tear up my blade and make all that dust. I'll be making numerous cuts to make the 6" strips. The cuts don't have to be pretty so I was thinking utility knife.

 

[SlyFerret]

I was under the impression that you cut Durock the same way you drywall. Score it and break it.

-SF

 

[jeffman3]

I was under the impression that you cut Durock the same way you drywall. Score it and break it.

-SF

That is how I did mine. Score it and break it. I had to make several passes with a utility knife to score it deep enough to break clean. Make sure you have extra blades, the one you use will be worthless when you done. (You are cutting cement)

 

[Hogwildz]

Agreed with the other. The pc I had even had a direction label both instructing to score with utility knife & snap and warning of cement & silicate product & dangers of dust when cutting with a saw.

 

[rsiros]

A utility knife it is... thanks for all the help!

 

[JimWalshin845]

Started the hearth project, and I'm trying to create a one inch space for some insulation to lay in. I would like to know the best way to make this "cavity". I have read numerous posts about using metal studs, but I have an extra sheet of Durock that I could cut into strips. Any thoughts and/or experiences?

Rsiros,

What are you using for insulation... I am very curious as per what you are doing here?

 

[rsiros]

Hi Jim... I have Roxul to insulate my hearth that I had to rebuild. I have a Hearthstone Homestead with 4" legs that needs a r-6.6. I tore up my existing hearth and will be using Durock strips to make a cavity for the insulation to lay in, then Durock over, then tile.

 

[Codeman812]

Hogwildz had posted about the utility knife b4, and that is how I cut mine this weekend. I really did not want to deal with all the dust from cutting with a power tool. My 1st time dealing with tile this weekend and I love it. I now have a lot more projects planned.

 

[rsiros]

I cut a few pieces over the summer for a tile project, and cut with a circular saw. A ton of dust, but I cut it outside with a dust mask and goggles. I'll be doing a lot of cutting to cut the strips, and I don't want all that dust, or to go outside to do all that cutting (2" of snow and mid 20's here today... I'm sure some of you further north will laugh).

 

[mikeathens]

If you're using durock "strips" to build up the hearth for air space, isn't your R value only as great as the layers of durock? I don't know that you can claim 1" air space if your supporting layer(s) of durock will be in contact with combustibles. If I remember correctly, a 0.5" layer of durock is only something like R-0.25. If you have two "strips, that onl R-0.5 - far from the R value specified for your stove. I could be way off on this...it seems you will have alternating "sectors" of high R value (air alyers) and lower R value (where the durock is stacked).

 

[rsiros]

I wondered the same thing, but it seems to meet with approval.

 

[mikeathens]

Also, you said that you would be putting insulation between the "stacks"? You're not talking fiberglass or other traditional insulation, are you? If so, that might also cause a problem...

 

[rsiros]

I have a mineral wool product called Roxul. I was advised to make an air space for it and not sandwich it. It's semi-ridgid and I originally wanted to sandwich it but was told not to.... hence the Durock strips.

 

[Hogwildz]

Hogwildz had posted about the utility knife b4, and that is how I cut mine this weekend. I really did not want to deal with all the dust from cutting with a power tool. My 1st time dealing with tile this weekend and I love it. I now have a lot more projects planned.

Ut oh, now the long list of projects begins, or lengthens. Just donlt let the OL find that list, or she will surely double its length. oog oog

 

[Hogwildz]

I cut a few pieces over the summer for a tile project, and cut with a circular saw. A ton of dust, but I cut it outside with a dust mask and goggles. I'll be doing a lot of cutting to cut the strips, and I don't want all that dust, or to go outside to do all that cutting (2" of snow and mid 20's here today... I'm sure some of you further north will laugh).

Its plenty cold enough for me here in PA. Don't need any further north Seems being at the base of the mountain, its a lil colder here than in town. They get rain, while we get snow.

 

[ansehnlich1]

I am not a professional, but this setup as I'm reading ain't good. I think your r-value needs to be 6.6 across your entire hearth. Now, how to do that is the question.

Maybe somebody should call those folks over there at HEARTHSTONE and ask 'em just how they figure a guy should achieve this 6.6 r-value???

A half inch of durock = .26 r-value found here......

(broken link removed to http://www.usg.com/USG_Marketing_Content/usg.com/web_files/Documents/Prod_Data_and_Submittal_Sheets/DrckCement_Board-Submittal_Sheet_CB399.pdf)

so 1 inch = .52 r. You'd need 13 inches of durock to get your r-value 13 x .52 = 6.76 r-value

 

[rsiros]

Should I sandwich the Roxul? Or perhaps use metal studs as others have done?

 

[Hogwildz]

Get yourself some micore 300. And read up on r values in the table here on hearth.com. That will give you better ideas of what materials offer the thinest profile with highest r value.

 

[Codeman812]

Actually I should have said "we" have a lot of projects planned. 1st thing that was mentioned was doing the whole dining room, ya just know the kitchen is way to close not to be done as well, then there's the downstairs bathroom with a bad floor that needs replacing across from the laundry room with the same problem.....I don't know how fun it is going to be after all that

Hogwildz had posted about the utility knife b4, and that is how I cut mine this weekend. I really did not want to deal with all the dust from cutting with a power tool. My 1st time dealing with tile this weekend and I love it. I now have a lot more projects planned.

Ut oh, now the long list of projects begins, or lengthens. Just donlt let the OL find that list, or she will surely double its length. oog oog