DIY Outdoor Fireplace and Concrete Pads

DIY outdoor fireplace, stone seating

Concrete or Dirt? That is the Question

cDIY Concrete slab in backyard with grass wood
Concrete slab is ready for cinderblock.

The other day my phone rang and it was a customer of Backyard Flare that had purchased a DIY construction plan for the Pima II design.  This customer was looking for information about whether he needed to build the fireplace on a concrete pad or whether he could just build it on the dirt.  This question comes in quite often so I wanted to address it again.  Concrete pads are necessary for a masonry outdoor fireplace.

Where You Live is Important

DIY concrete pad deck level outdoor fireplace
Finished concrete is ready for block work

Think about all the places you have been and the ground you have walked on.  There’s Arizona with ground so hard that it almost takes a jack hammer to dig down a couple inches.  Then there’s Florida with gorgeous sandy beaches, but that sandy soil reaches inland too.  You have the northeast states that have frost lines so deep, that it’s a wonder that it ever thaws out. And we can’t forget the northwest that gets a lot of rain that could create washout conditions.

There is our dilemma with phone calls relating to how thick or whether a concrete pad is necessary.  Even here in Arizona, I always build my outdoor structures on concrete.  This is for peace of mind so if there is any ground settling, the structure will hopefully be okay.

If a masonry built structure settles, and it has been built on a running bond (stair step) block pattern, the cracking will look like a stair step going up.  The blocks will often separate at the seams, not crack.  This is not the way you want your outdoor structure to end up, because you spent your hard labor to build it.

What should you do?

DIY outdoor fireplace, stone seating
DIY outdoor fireplace on new poured concrete pad.

Do it right from the beginning and pour some concrete. Support that structure and keep it from settling and cracking.  Now you say, that’s all fine and dandy, but how thick does the concrete need to be? There’s an issue with that portion of the concrete pad question in that there is no “one answer” to that question.  There is no recommendation that we can give you because your geographic area and soil will dictate the answer.

Remember all the different soil types we cited a few paragraphs ago?  There are so many variables that exist that will need to be addressed and recognized before a concrete pad thickness answer can be formulated.  Our advice is to seek out some professionals in the concrete industry and ask.  Go to Home Depot or Lowes and see if there is a person who used to pour concrete for a living that is working there in retirement.  They are sometimes a wealth of information.  Go to the internet and search for recommendations based on your soil type and geographic area.  Again, lots of information.

Test Time

So, what have we learned?  I always recommend a concrete pad for an outdoor masonry built fireplace or kitchen.  There is no hard and fast recipe that applies to everyone that they should follow to pour the pad, so go find your local resources.  They’re out there.

If you would like to discuss your backyard outdoor fireplace or kitchen and would like to learn more about the DIY world we love so much, visit Backyard Flare.  We can help make it a reality, saving you thousands of dollars.  Give your backyard a face-lift and beautify your outdoor space.

Thanks for reading and as always, happy building.

Dan Heston
Backyard Flare, LLC
Tucson, Arizona

Author: DIYoutdoorfireplaces

I am the founder and owner of Backyard Flare, LLC in Tucson, Arizona. We design outdoor fireplaces, outdoor kitchens, and pizza ovens and provide the construction plans needed by DIY savvy homeowners to build their own backyard structures.

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