Hearth

Roughing in the Frame and Hearth Preparation:  Considered many options for bridging front opening for the door.  Ended up with simply 2X8 pressure treated board cut to size and resting on regular bricks (preventing it from possible rotting) to create a storage opening.  Picture 4 shows the roughing and Picture 3 shows the 4 inch blocks in anticipation of the hearth.



While shopping for the lumber and 4 inch blocks I wasn't sure if I had a masonry bit to secure the board to the blocks.  I choose not to buy the bit.  Murphy's Law in full effect:  had to make a trip to the local hardware store for a $3 dollar bit.  



Picture 3

Picture 4



 Leveling:  My patio has a bit of an incline towards the storm drain in the corner and this was the only difficulty in laying the blocks.  Additional cement and tapping with a mallet did the trick.  I did not fully level the blocks with the first layer but slowly as I added more layers of blocks.

Concrete Slab and Insulation:  This is where I did most of my research.  Every article I read suggested a different way of pouring concrete.  Some builders had the concrete suspended on rebar which probably is the most effective way of preventing the heat from dissipating.  That particular process required building of a frame with 2X4s and topped with 3/4 inch plywood.  Rebar resting on the blocks, concrete is poured.  Rebar holds all the weight.  Once cured, 2X4s and plywood is removed. 

I choose to go a different way since it seemed a lot of work to build the frame.  Made another trip to the HomeDepot and purchased 1/2 inch thick backar board (cement boards typically used in the bathroom showers before the tile is installed), cut it to the correct dimensions (30X30 inches) and layed it on the top of the base resting on the full blocks. 

At this point I had a 7 1/2 inch deep "pocket" to pour the concrete.  But before pouring the concrete, I layed 29 inch rebar and layed it about 6 inches apart ensuring that the rebar would weigh on the blocks.  Mixed the concrete and poured about 2 1/2 inches on top of the backar board and the rebar.  That left me with 5 inches of depth for insulation and final layer of sand and clay.  Unfortunately I forgot to take picture of the steps described above.  Advantage of this approach is that one does not have to remove the backar board, it is part of the hearth.

Insulation Layer:  Many web sites recommend Perlite, Portland Cement and Lime mixture for the insulation layer.  I went with Vermiculite and Portland Cement with 5:1 ratio.  Looking back, I could have probably done a 10:1 ratio for better insulation. 

This was a good stopping point for the insulation and the slab to fully cure.  Since I was flying out of town, I covered the base with tarp in case it rained.



Picture 5

 Vermiculite and Portland cement were purchased at Menards.  I had a difficult time finding the vermiculite since the bags are not labeled as such but as "Loose Attic Insulation".

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