DYI Hearth pad - In order: 5/8" plywood, 1/2" Micore 300, 1/2" Durock, and ceramic tiles

[Gmarcil]

I am planning to build a large 115" x 64" hearth pad for a Pionner Princess cookstove (needs a R-valued of 0.6) in our kitchen. The pad is extended for esthetics to accommodate a wood box and word stove accessories.

Does anyone have an installation guide or the proper procedures to build the pad on top of an existing vinyl floor?

Questions:
1- Should the vinyl flooring be removed?
2- Should the 1/4" plywood be removed to be left only the existing 5/8" plywood floor?

Then I plan to install the 1/2" Micore 300, 1/2" Durock, and ceramic tiles.

3- Can the Micore 300 be simply layed down snug or do they need to be glued, screwed or cemented to the plywood floor?

4- When installing the Durock boards on top of the Micore 300, should they be glued, screwed or cemented?

Thanks for any tips and professional advices

 

[begreen]

It can sit on top of the vinyl floor as long as it meets or exceeds the required insulation value. The cement board requires being screwed every 8". Micore is too porous for cement to adhere well to it. It's ok to use longer screws to make a sandwich of the cement board on top of the micore with no cement, screwing every 8" with 1.75" screws. If you can't find cement board screws long enough, you may need to use drywall screws for this purpose.

 

[Gmarcil]

Thanks Begreen.

The R-value required for this stove is R-value 0.6 and the total R-value of the material here is:
1.03 - 1/2" micore 300
0.25 - 1/2" Durock cement board
0.02 - Ceramic tile

Total R-value - 1.3 which exceeds the thermal requirements of 0.6

I certainly intend to use cement board screws as I have been told that if one uses drywall screws with Durock boards, they will commonly:

• Break when driven
• Corrode over time
• Lose holding power

A concern I have is the thickness of this hearth pad floor which amounts to almost 1.5" thick
(1/2" micore + 1/2 durock board + thinset and porcelain tiles)

A concern This thick hearth sub-floor might cause accidents if people trip on the edge of this hearth while accessing to the cookstove for cooking!

Do you think it would be acceptable to use 1/4" Durock boards instead of 1/2" to reduce the tickness of the hearth floor?
It would still meet the thermal protection requirements. However, I wonder if the hearth would be strong or rigid enough to support the weight of the cookstove ( 630 pounds)? I am concerned about tiles potentially cracking!

How do you folks think?

 

[EatenByLimestone]

What will you border the hearth pad with? Your height might be hard to find trim for depending on your plans.

 

[Gmarcil]

Not sure yet. I will probably need a custom made oak trim cut with at no more than 45 degrees.

 

[begreen]

I would not use 1/4" cement board. Find a piece of micore and push your thumb into it. The product is soft. It's full of air.

Let me know if you find 1.75 or 2" cement board screws. They are not available at the big box stores or our local lumber yard. Once captive and the mortar has dried, I am not too worried about drywall screws rusting out. But one could use stainless screws.

 

[Gmarcil]

Thank you again Begreen.

Thanks for confirming the durock boards thickness!

There are 1 5/8" cement screws for cement panels available at home depot:
#9 x 1-5/8 in. Star Drive Serrated Head Cement Board Screws (575-Pack) or
#9 x 1-5/8 in. Star Drive Serrated Head Cement Board Screws (140-Pack)

Have a great day!

 

[begreen]

Thank you again Begreen.

Thanks for confirming the durock boards thickness!

There are 1 5/8" cement screws for cement panels available at home depot:
#9 x 1-5/8 in. Star Drive Serrated Head Cement Board Screws (575-Pack) or
#9 x 1-5/8 in. Star Drive Serrated Head Cement Board Screws (140-Pack)

Have a great day!

Better, but I'm not sure if they will be long long enough, especially if on sheet vinyl flooring.

 

[Gmarcil]

Oups, you got me thinking about the exiting floor.... Yes 1 5/8" screws would be too short indeed because I also have 1/4" plywood under the vinyl.

So a better choice would be: #9 x 2 in. Star Drive Torx Bugle Head R4 Multi-Purpose Wood Screw (110-Pack)

Highlights​

• For use in wood, particle-board, cement fiberboard, plastic, sheet metal
• Star drive eliminates stripping for improved productivity
• Zip-tip point eliminates the need to predrilled and provides easy starts into wood
• CEE thread enlarges hole to reduce splitting, thus eliminating rework
• W-cut thread design acts as a saw blade providing clean cuts through all wood and fibrous materials
• Zip-tip allows for no-pre-drilling and 1-step application
• Both zip-tip and w-cut thread design help eliminate splitting of material
• Cutting teeth cuts wood fiber and provides flush seating
• CEE thread reduces torque and friction during screw-in action
• Common project applications: remodeling, fencing, storage, cabinets, framing
• ESR-3201 approved for structural applications
• Cutting pockets underneath head allow screw head to countersink flush with material
• Ground contact lumber approved for worry free use in pressure treated lumber
• Climate coating resists corrosion

Cheers!

 

[begreen]

Yes, that's more like it.