Is cracking of Block normal? Pict

[caspian]

I ran out of time last year and only built my fireplace (didn't face it with stone). This year I'm working on the pizza oven, so facing will take place next year. I noticed cracking of the block. All voids were filled with concrete and rebar, but I'm not thrilled to see the cracking. I'm guessing it is from last winters freeze/thaw. Is this something to worry about, or common due to the nature of the build?

[IMG][/IMG]

[Tscarborough]

Re: Is cracking of Block normal? Pict

Normally, when cracks travel through a block like that it is not normal, it is indicative of foundation failure. Normal shrinkage cracks stair-step the joints.

[caspian]

Re: Is cracking of Block normal? Pict

I have cracks in the same location on the other side of the fireplace. Am I totally screwed? I have about a 5" base of concrete with rebar. It is on top of a few inches of chips and dust compacted. On top of the pad I put 2 layers of concrete block filled it with concrete. Total base thickness is 21" concrete/concrete block with concrete.

Will it find a spot and stop? Ugggg. This is not in a location where I can easily get a bobcat to redo.

[Tscarborough]

Re: Is cracking of Block normal? Pict

It appears that the slab (assuming that is what we see at the bottom of that pic) has a substantial crack in it.

[Tscarborough]

Re: Is cracking of Block normal? Pict

How big is the fireplace, do you have an overall pic?

[caspian]

Re: Is cracking of Block normal? Pict

It's huge. The grate is 4' wide.
So I should dig to the sides of the foundation and look for cracks. If (hopefully) there are none, I repackage and top off with rock to prevent erosion. If there is a crack in the foundation, what do I do?

[Tscarborough]

Re: Is cracking of Block normal? Pict

Best case scenario, it settles and you can proceed. Worst case, it will continue to move and mirror through you finish materials and eventually fail. If compaction was done correctly on the base and sub-base, you will probably be OK.

[caspian]

Re: Is cracking of Block normal? Pict

This was my first time and in hindsight would
Have done a thicker layer of chips and dust and thicker pad. That is water under the bridge. I had no idea how much this thing would weigh.

I can only hope the structure of the fireplace will aid in minimizing distortion. The excessive rebar and concrete through the blocks may help it.

Thanks for your insight. Hopefully someone planning a build will so 200% on the base and not redo my mistake.

[Les]

Re: Is cracking of Block normal? Pict

It appears that it is leaning to the left - it that just the picture?

[thickstrings]

Re: Is cracking of Block normal? Pict

If it gets worse, I might consider calling one of those companies that pump a cement type mixture under you slab to level it....It works on house foundations......

[caspian]

Re: Is cracking of Block normal? Pict

Just a follow up to this situation. I dug out around the foundation and there is no failure.

The foundation consists of the following: 5" chips and dust compatced, 5" concrete with rebar, 2 layers of CMU filled with concrete to bring the height up to the patio.

The cracks stop at the bottom layer of the actual oven. There are no cracks or failure in the CMU or poured base.

My theory is that the cracks in the walls could be caused by building hot fires (its a large fireplace) during cold months whild there is water in the wall. That's the only thing i can figure.

The interior of the fireplace is lined with splits and doesn't offer much insluation to protect the CMUs (which are filled with rebar and concrete).

I am planning on adding a layer of full brick firebricks to the interior to provide some protection to the CMUs.

Any input or advise? Has anyone seen this before with underprotected walls?

Thanks

[stonecutter]

Re: Is cracking of Block normal? Pict

Just a follow up to this situation. I dug out around the foundation and there is no failure.

The foundation consists of the following: 5" chips and dust compatced, 5" concrete with rebar, 2 layers of CMU filled with concrete to bring the height up to the patio.

The cracks stop at the bottom layer of the actual oven. There are no cracks or failure in the CMU or poured base.

My theory is that the cracks in the walls could be caused by building hot fires (its a large fireplace) during cold months whild there is water in the wall. That's the only thing i can figure.

The interior of the fireplace is lined with splits and doesn't offer much insluation to protect the CMUs (which are filled with rebar and concrete).

I am planning on adding a layer of full brick firebricks to the interior to provide some protection to the CMUs.

Any input or advise? Has anyone seen this before with underprotected walls?

Thanks

Yup, I have.....when ever the firebrick is directly bonded to the cmu. Usually there is a air space...a thermal break, especially on outdoor fireplaces.

I would remove the splits and build a new box with full size FB, leaving a 1" gap between the cmu and the FB.

Then you should work on getting some weather protection on the cmu before winter comes. Once you get cracks the damage will get worse faster. If you don't have time for anything permanent, then coat it with Thoroseal at least.

[caspian]

Re: Is cracking of Block normal? Pict

Thanks for the advise. I will patch the cracks and seal it with Thoroseal.

Should I fill the 1" void with vermiculite or just leave it open? I am guessing open is better in case water gets in there through the chimney.

[stonecutter]

Re: Is cracking of Block normal? Pict

Open or loose perlite/ vermiculite.

[caspian]

Re: Is cracking of Block normal? Pict

Will this work just as well to get me through the winter? Price seems better and this project is draining me.

Heavy Duty Waterproofing Base Coat at Menards