Wednesday, May 15, 2013

Back In The Mud

I finally got the hearth poured under my gas fireplace so I thought I'd show ya'll a quick post on how I did the forms.  It's fairly simple really.  The top of the 2x4's are the permanent framing that will hold up the slab.  That strip of darker plywood on the outside is the edge form that will drop down from under the concrete once it has cured.  The whitish looking board is the side of the edge form that will drop off later also.

Here you may be able to see a little better.  The bottom edge form is basically 2 pieces of 3/4" plywood screwed together at a right angle and then screwed to the framing.  I wedged it in places to get the flat part level.  After that was on I screwed the edge form on.  All of these pieces were ripped to the correct widths so I could use the edges as grade.  Am I explaining this right?  Everything that was to come off later was also oiled so it would release easily.

I found a new mix for doing the slabs and counter tops and I am very pleased with it.  It is one part Portland cement, 2 parts aggregate (89-10 in this case) and 3 parts sand.  That seemed like a lot of sand to me but it works fine and finishes wonderfully.
I bent a #3 piece of rebar to go round the outer edge and then filled in the inside with some wire mesh and chicken wire.  Whatever ya got just make sure to pull it up in the mix and not let it get trapped on the bottom.

I also used a clear silicone caulk to seal all the cracks because a fair amount of water is going to weep out of a slab.  As you screed and trowel it down, some slurry will come over the edge so I put some old crappy towels down to catch my mess.  Of course, it helps that I don't have finish floors down now to protect.  I put a fan on this from both sides to kinda help the water evaporate.  A pool will form on the top after you float the slab down flat and you don't want to start working it until that disappears or you'll just work the water back down into the concrete.  As the water evaporates you can see the surface start to tighten up and then you can start with a slick trowel.  One or two passes and then let it rest to tighten up a little more.  And repeat until you get the surface you want.  Well, it's harder than that but I can only explain to a point; it's something that you just have to see and try.
I have wrecked the edge form off at this point and am going to smooth the corners and seal it before too long.  Hopefully.  Then I can start running the slate tile!!!  Yay!!
Jack and I also finished installing the pendant light in the kitchen and they look fantastic!!  I'll show that soon.


Ed said...

I'm a little confused as to why the slab was built in the air? I'm guessing that is just the height you wanted it at. What are you going to finish with between the slab and the floor?

edifice rex said...

Hey Ed! yeah, I just didn't like the looks of it flat on the floor. I mean, it's not really a functional hearth but just for looks. The space will be filled in with slate tile.

HermitJim said...

Looks pretty good to me. Of course, you make it look so easy!

What a gal!

edifice rex said...

Hey Jim! thanks! well, this was pretty simple.