The Fireplace - Part Two

In this post we will start again with the adding of the stone.  In my past posts about installing the stone veneer on various projects, I installed metal mesh before adding mortar to the stone.  Since I have cinder block for the bottom portion of the fireplace, I did not add mesh because the stone will stick to the surface since it is already irregular and porous. The only difference when adding the stone is that you should wet the cinder blocks with water first.  This is because the dry cinder blocks will otherwise soak up all the water in the mortar and it will not cure and hold properly.  Below you can see the progress on the stone for the lower part of the fireplace.  I am still cutting each stone to make a tight fit so it took probably close to 35 hours to do all the stone.

Since the top half of the fireplace is still wood covered in tar paper, I added mesh so the rest of the stone would stick to it just like I did on all my other columns.  You will notice in the picture below that there are pavers being placed for the hearth.  I am using two levels of pavers instead of pouring a solid concrete slab to keep the weight down.  The pavers will be covered with a fiber reinforced concrete in the future so it will still look like a solid slab when I am done but it will be half the weight.  The pavers are mortared in place and since they are concrete as well, they will attach to the cinder block and will not be moving anytime soon.  I also added welded wire mesh between the layers of pavers to help if any settling does occur and to reinforce the area for seating.  

Originally I planned to just leave the inside of the firebox the cinder block and then paint the interior with black high heat paint.  Since the fireplace was turning out so well I decided that I really needed to finish the inside of the fireplace in brick to make it look even better.  Most fireplaces use firebrick which is more of a ceramic than a brick to hold up to the high heat of wood fires.  Under repeated high heat, a normal brick deteriorates and will eventually crumble.  Since this fireplace is only natural gas, the temperature does not get hot enough to deteriorate regular brick.  I decided to use a blonde thin brick that resembles fire brick.  This brick is only 1/2” thick so it is made for decoration and is actually cut from the face of a full size brick.  This type of brick is normally around $15 a square foot. To do my fireplace I needed about 40 square feet so it was going to be quite expensive.  I found a guy on craigslist that sold me some leftovers he had for a little over $1 a square foot.  I paid $45 for all of it.  Below was my great haul laid out on the floor in a herringbone pattern.

It turned out to be a little tricky to install the brick.  I used mortar again but had to wet the cinder block and the bricks to keep the mortar from drying out too fast because both materials were so porous.  I also had to take very precise measurements because with this pattern if the bottom row is slightly crooked, each row above it gets a little more off until it is all messed up. In the below picture you can see the back completed and all the cuts I had to make everything fit. 

I waited a day for the back to fully cure before I started on the two other sides.  The bottom of the firebox will be covered in sand so I did not add brick to the bottom. Below is the final product of all the brick work.  It turned out real well but turned out to be quite the task.   

For the fireplace I really wanted to have decorative molding but was having trouble figuring out what to do.  I had seen moldings made out of Styrofoam and then covered in stucco but they are a fortune and I really wasn’t sure how well they would hold up in Colorado weather.  I was reading online about making fountains out of concrete and I realized that the same technique could be used in my project so I decided to try and make the moldings out of fiber reinforced cement.  The cement is called Quickwall by Quickrete.  This stuff may be my new favorite building material as I am finding so many uses for it!  I first made a pattern as to what I wanted the molding to be.  I gave this to my brother who went to my Dad’s sheet metal shop and made a mold for me. I had my brother make the mold longer than I needed so that I could change the length of the piece each time depending on what I needed.  In the below picture you will see the small mold I had made.  I cut pieces of metal to fill in the ends and left extra metal so I could use clamps to hold it together.  Since I would need to make almost 20 pieces of the small molding, I wanted to be able to re-set the mold quickly.  

I only had one mold, so every night after work I would make a new piece.  I started by spraying the inside of the mold with vegetable oil.  This would help me remove the concrete once it started to harden.  The concrete I mixed to a very thick constituency almost equal to toothpaste.  I would then fill the mold half way with concrete and then tap the sides and bottom to make all the air bubbles float to the surface.  I would then add the second half of the concrete and smooth out the top.  The next day I would pull out the casting and then re-set the mold to make another piece.  Here is a pile of pieces I had already cast.

Since these pieces were longer than what I needed and would not have perfectly squared edges on the ends, I ran them through my wet tile saw to cut everything straight.  I also cut some pieces at 45 degree angels to miter the corners.  These pieces were then attached by using mortar and held in place with braces until the mortar dried.  Below is a picture of the smaller pieces installed.  There are gaps between the pieces that will be filled in with more mortar in the future to make it look like grout lines. 

The next step was for me to cast the larger pieces of molding for the fireplace.  Again like the last mold, I made a template and my brother folded up the metal for the form.  Because these pieces would be much larger (almost 40 pounds each), I needed to create a different type of mold.  Because the weight of the concrete would bend the mold slightly if it was unsupported, I needed to create an additional form for the mold to sit in to the mold would stay exactly the same for each casting.  I did this by creating a wood frame that was a little larger than the metal.  This piece of molding was to have a large arch in the middle so I needed to make sure it was supported.  I did this by placing a piece of plastic over the back of the mold and then setting it in the frame.  The next step was to fill the void that was created with expandable spray foam so that the material would expand to the unique shape and give support.  Once the foam dried I cut the excess foam away and it gave a very sturdy backing for my mold.  You can see the completed mold below.  

After I had created many of the smaller castings, I found that it would be helpful if I could reduce the weight of the larger castings and also create an easier way to attach them to my fireplace.  First of all, I started using large blocks of high density foam to stick in the center of the mold.  This reduced the weight quite a bit but did not reduce the strength since they were encapsulated in the fiber reinforced cement.  Below you can see a picture of a cut-away on one of the pieces where you can see the foam. 

 The next change was that I added five inch bolts to the back of the casting while it was wet.  I added a large washer on the top of the bolt to help it grab better in the cement and then buried about half of the bolt in the wet cement.  You can see this in the pictures below. 

My brother then helped me lift the heavy pieces in place with mortar on the back of the pieces.  We pre-drilled holes for the bolts to go through the fireplace and then attached washers and nuts to the back side to not only help support the piece while the mortar dried but to also be the main anchor point.  Below you can see all the pieces mounted.  You may also note that some of the pieces are cut long.  This was so I could grind the extra cement away to make the contour of the ends match the adjoining pieces.  

After the main mantle was installed, I continued to work on the stone for the rest of the fireplace.  Since there is a curve towards the top, I had to cut each stone by hand with a slight angle so that it would look correct on both sides.  You will also notice in the below picture, that once the point on the chimney is reached where there is no curve, I had to make sure that all my lines of stone lined up so it looked like one level all the way around.  This wound up being no easy task since there is no standard width to any of the stone and I had to account for the difference in the prior few rows so it would look correct when I got to that point. 

In the above picture you will see that I attached the top molding a little differently.  Since there is no stone above the molding, I would not have any extra pressure to help hold the stone in place.  For this I attached a metal edge to sit the concrete molding on.  I also embedded some metal straps into the concrete while it was drying so that I could screw it into the top of the frame.  The top of the fireplace is actually covered with a piece of galvanized metal to keep rain and snow out and I sloped the top towards the back for the water runoff.  Here is an up-close picture of the mounting that gets covered up by mortar and stone so it isn't even noticeable.

Unfortunately I did not really take many pictures of the inside workings of the fireplace as I was building it.  I made a cardboard template of the top of the fireplace opening and had my brother make a chimney cap to funnel the heat.  I then cut a hole on the top of the cap and ran metal flexible flue liner up through the top of the fireplace and attached a vent to the very top of the fireplace.  The flue liner directs all the heat out of the top but also keeps all the heat away from any of the wooden parts of the fireplace.  I will build a decorative cap to cover this up at a later point.  In the below picture you can see the metal vent.

The back of the fireplace has since been covered with a coat of fiber reinforced cement to match the rest of the fireplace.  Once it gets warmer I will paint it a color that will match the stone but since it is only seen from the street, I did not go to the trouble of putting stone on the back.  There will also be an access hatch on the back so I can get to the gas line and also use it for storage of outdoor torches and such.

There is still the task of covering the paver hearth with the fiber reinforced cement and grouting in the gaps between the cement castings, but that will all happen this summer when it is warmer.  You will see that everything is now cleaned up and I also finished grinding all the moldings to the right contours in the corners.  I am really happy with how it turned out and just wait until you see how it works with the pergola I am building on this side of the house.  I figure between my brother and I, we spent about 75 hours on this fireplace with most of it being the stone and brick work.  My schedule shows me completing this part of the yard in the very early summer so keep watching for updates soon.  So I will leave you with a few pictures of the (almost) finished product.