Featured My Fire Pit build project using retaining wall blocks & galvanised rim

Discussion in 'Building DIY, Machinery & Tools' started by Mark, Aug 5, 2015.

  1. Mark

    Mark Founder Staff Member

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    Here's how I made my fire pit out of regular retaining wall blocks/bricks and a galvanised round garden bed for the central steel rim.

    Overall the build took about 6 hours mostly due to digging and measuring/levelling out to make sure I got it right the first time. I have to say, I'm really happy with how it has turned out!

    fire pit made from retaining wall bricks and galvanised centre rim.jpg
    Background

    To be honest, building a fire pit was never in my mind - it was just something I hadn't thought of until my wife suggested it. We were talking about buying some kind of outdoor wood oven and I had been researching several of them including pizza ovens and various other cooking devices, which used wood as the fuel since we have so much free wood from all the fallen trees on our property lately.

    My thought process was to find something I could use to cook with, in particular, to roast meat like our pekin ducks, which we grow to eat. I don't know why but an open fire pit didn't occur to me because my focus was purely on some type of oven. Then, my wife asked if I had considered a fire pit like a backyard campfire except built to look nicer and I admitted I hadn't but the seed was planted and a quick Google found heaps of inspiration!

    I got to thinking could I build a fire pit which was: cheaper than an off-the-shelf outdoor wood fired oven; easier to make than a DIY pizza oven; and give me the ability to roast our ducks? The answer was YES!

    Considering how I'm not the best handyman, I wanted my fire pit to be as easy as possible to build. Materials had to be easy to obtain and I didn't want the build to be overly technical or require craftsman like skills to construct.

    The cooking concept is simple - you guessed it - a spit bar powered by a simple battery operated unit and that's my "outdoor oven/wood fired cooking device" complete :)

    Materials

    Size: Before I purchased the materials I obviously needed to work out roughly what size I wanted the fire pit to be. You could easily get carried away and build a large pit with visions of roasting a buffalo over it but in all practicality a large fire pit takes more fuel to run, is harder to stoke/control, gets too hot, difficult to talk over it, and takes more to build. On the other hand, you don't want a fire pit that is too small either.

    I decided the internal area should be around 1 metre (about 3 feet) give or take a little and this would be about right for general cooking (even a small pig) and comply with other aspects/expectations of what a campfire should perform like. When you really think about a proper campfire it doesn't need to be huge to be effective and a bonfire looks spectacular but it's pretty stupid really.

    When the outer wall is taken into consideration an internal measurement of about 1 metre seems right as this would bring the total width of the fire pit to just over 1.5 metres which will accommodate most commercially made spit assemblies perfectly. In the end, I was only able to source a 90 cm inner rim (just under 1 metre) so I worked off that and I reckon this size turned out to be spot on.

    Deepness or height was a factor also, I wanted the fire pit to be raised enough to contain the fire appropriately and so the walls could act as a visible barrier for safety reasons, but it couldn't be too deep that it hindered management of the fire or the heat for the spit. I decided on a foot or 40 cm deep was about right, which meant 3 x blocks high (allowing for some digging in) was good enough.

    Keeping it simple I decided to use the following materials obtained locally to build the fire pit:

    • Retaining wall blocks - 215 mm (about 9 inches) wide Borderstone (has the lip underneath to stack on top of each other in a tiered fashion) x 53 @ $2.05 each = $108.65 These medium sized blocks look good and are designed for stacking plus are easier to make a smaller neater circle than the larger blocks.
    • Inner rim galvanised round garden bed - Tumbleweed brand (from Bunnings), 90 cm wide x 40 cm high @ $104. This rim has several purposes: it protects/insulates the bricks from direct fire therefore they should last longer; it makes for a neater and straight wall because the blocks tier inwards as they stack so the wall would be staggered otherwise; and gives integrity/strength to the wall by having something the blocks can be placed against.
    • Masonry adhesive - 1 x tube @ $10.50 This is used to stick the top row of blocks onto the second row and fill any gaps between each top row block.
    • Sand/course sand - 6 x 30 kg bags @ $7.90 = $47.4 Yes, I could have got a trailer load for cheaper but for convenience sake I got my paving sand from Bunnings. This was used as a base to lay the blocks and to also fill the gap between the blocks and the inner galvanised rim. It doesn't really matter if you use sand or "course" sand - I used a mixture of both.
    Total cost = $270.55

    Build


    Here's the steps I took to build my fire pit.

    Step 1 - Dry run

    I did a dry build in the location I wanted my fire pit to get the size and positioning right. I located the pit away from overhanging trees and in a position convenient to our picnic area but not where people are always walking past.

    Once I was happy with the build I marked the base with stencil builders marker spray paint allowing for an extra few inches around the base.

    fire pit step 1 measuring out position.jpg

    Step 2 - Digging out fire pit and levelling off

    My area was uneven (hard to tell by the pics) but I needed to dig out the pit several inches more on one side to ensure the pit was level. I continued to lay blocks around scraping out and levelling off each block until the whole ring was as level as possible.

    Fire pit building step 2 dig out and level.jpg

    Step 3 - Position rim and compact paving sand

    Position the galvanised rim central and pour in paving sand around outside then compact it down by walking over - the sand should be a few inches deep at least.

    building fire pit step 3 position rim add paving sand for blocks.jpg

    Step 4 - Lay first level of blocks

    Lay the first level of blocks as evenly as possible around the rim ensuring about a 2 inch gap is left to allow for the remaining levels (2nd & top) to tier inwards as it is built up otherwise the top level of blocks won't fit. I used a rubber mallet and spirit level to lightly tap the blocks together into the paving sand and make them all straight and square.

    building fire pit step 4 position bottom blocks.jpg

    Step 5 - Build levels 2 and top plus set rim height

    Place the second level of blocks on and try to position each block centrally over the gaps between the two bottom blocks. Depending on the size of the rim this may not work out exactly and you will find some blocks out of alignment - I wasn't too concerned about this and just tried my best to get each layer of blocks as staggered as possible to the one below. Note these type of retaining wall blocks cannot be stacked flush on top of each other due to the lip on the base and are designed to lock in behind the bottom block as they step back.

    I placed the top level of blocks on at this stage (even though they were to be removed in the next step) because I wanted the rim set a few inches below the brickwork so I worked out the height by laying the top blocks to find out how far the rim needed to be dug down. See how in the image below the rim is too high?

    This is probably a good time to mention gaps between blocks: unless you are prepared to cut blocks to size or you're lucky for them to fit together perfectly do not expect all blocks to fit together flush because it's nearly impossible to do and will likely drive you nuts trying. There will be some gaps here and there which will be filled by paving sand and masonry cement so don't be too worried about getting the blocks exactly right just fit them together as good as possible. On a side point, smaller blocks (edging blocks) are best for making circles and could be used instead of the medium sized blocks; however, you need more of them, the structure isn't as strong, and I don't think the build looks as good...

    building fire pit step 5 position all three levels of blocks.jpg

    Step 6 - Dig in the rim

    Pretty self explanatory, I dug the rim down until it was about 1 - 2 inches below the top level of blocks.

    building fire pit step 6 remove ring dig down.jpg

    building fire pit step 6b remove ring dig down place back.jpg

    Step 7 - Sand between blocks bottom and level 2 only

    I then removed the top layer of blocks and filled the gap between the bottom two levels of blocks and the rim with sand. The sand gives extra strength and insulation for the retaining wall circle. I also pushed sand into the gaps between the blocks. It's best to add sand now rather than when the top level is on as it is a bigger gap between the blocks and rim at this stage and therefore easier to do.

    building fire pit step 7 fill sand up to level 2 brick.jpg

    Step 8 - Glue/cement the top layer of blocks on

    I found cementing only the top layer of blocks on with masonry glue was sufficient enough as the bottom and middle levels were very secure without needing cementing in or gluing. Once the final layer of blocks were positioned I then also used masonry glue to seal the gaps between the blocks.

    building fire pit step 8 cement top row blocks.jpg

    building fire pit step 8b cement top row blocks fill gaps.jpg

    Step 9 - Fill remaining gap between rim and top level of blocks with sand.

    I finished off with topping up the gap between the top circle of blocks and the rim with sand - there should be just a slight gap large enough to get fingers in and push the sand down so it's compacted.

    building fire pit step 9 top up with sand.jpg

    Step 10 - Let dry overnight and clean up the next day

    Then, it's just a matter of leaving the fire pit to dry and the next day brush off the sand, perhaps sand off some of the excess masonry glue from the top blocks, if required, to give the pit a better finished look but otherwise that's the job done - easy.

    fire pit build step 10 complete.jpg

    fire pit build in bbq picnic area step 10a complete.jpg

    I hope you enjoyed my fire pit build or at least got a few ideas about how you would like to make your own.

    Please feel free to ask any questions or add your own hints, tips, or ideas about making a fire pit to this thread.

    I'm hoping my spit rotisserie will arrive soon in the post and when it does I intend to make the spit a permanent fixture over the fire pit. I'll be processing about 4 ducks soon and giving the whole "fire pit'n spit" a good test run at a family BBQ in a few weeks time - fingers crossed it all goes to plan!

    It'll be roasted pekin ducks and marshmallows for everyone! :cheers:
     
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  2. stevo

    stevo Backyard Farmer Premium Member GOLD

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    gees that looks pretty flash. A little bit classy, so I can imagine a nice looking entertainment area being built around it over the coming years. Now I need one, but don't really have a place for it at the moment. Nice job :twothumbsup:
     
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  3. Mark

    Mark Founder Staff Member

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    Cheers Stevo!

    I agree about improving the entertainment/picnic area and give it a good upgrade. Perhaps some paving and a gazebo ; )
     
  4. Steve

    Steve Valued Member Premium Member

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    Yeah the wife has put in an order for a fire pit at our new place.
    My project list is 100 miles long at the moment! o_O
    Some good ideas in there Mark and its something I'll come back to once it get's higher up my list.

    Cheers
     
  5. Mark

    Mark Founder Staff Member

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    Being a crafty your fire pit will probably put mine to shame @Steve :D

    Cheers mate!
     
  6. Steve

    Steve Valued Member Premium Member

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    Nah mate, it'll be over-engineered and built with stolen materials, I mean they fell off the back of a truck :smug:

    If only the wife had as much faith in my construction abilities as you....:cheers:
     
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  7. Ash

    Ash Valued Member Premium Member

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    You can't tell me you're not a handyman Mark.
    That's a decent construction, and a great tutorial on how it was all done.
    Thanks!
     
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  8. Mark

    Mark Founder Staff Member

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    Thanks Ash - I still feel like a hack though... :D
     
  9. Mark

    Mark Founder Staff Member

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    I forgot to post the video I made on building this fire pit... I thought I had :)

     
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  10. Mark

    Mark Founder Staff Member

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  11. Mark

    Mark Founder Staff Member

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    Guys, just thought I'd mention a different idea I had put to me by a user on YouTube for step 7 instead of using sand as insulation between the blocks and the rim you could use a perlite and cement mix pour that in as a gap filler and once set it would also be great insulation!
     
  12. letsgo

    letsgo Valued Member Premium Member GOLD

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    Wow well done, looks great. :cheer:You need to give yourself a bit more credit with the handy man stuff, you do a pretty good job and at the very least you are prepared to give it a go :chuffed:
     
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  13. Mark

    Mark Founder Staff Member

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    I must admit I'm pretty chuffed with my fire pit build - there's a whole lot a satisfaction one gets from making something whether it be a DIY fire pit, chicken feeder, baking a cake, or preserving their own home grown food... ya can't beat it I reckon!
     
  14. stevo

    stevo Backyard Farmer Premium Member GOLD

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    How's this going Mark? I assume it will be used a bit over xmas?
     
  15. Mark

    Mark Founder Staff Member

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    It's great Stevo, we're going away for Xmas but will probably fire it up around NY - it's had several uses and I'd say been a total success and I'm glad I built it.

    One thing I will need to do is fill that gap between the bricks and rim with something other than just sand because the sand has sunk in places etc. I'm thinking of pouring in a perlite and concrete mix (I'll have to research how to mix that) as this is supposed to form a good firebrick and insulation - it might work better than the sand...
     
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  16. Comfort

    Comfort Well-Known Member Premium Member

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    My version. The insulation between the blocks and the liner is a combination of sand cement and vermiculite. The block stay cool no matter the fire inside.

    I made it last weekend and it's having its second outing tonight.
     

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  17. Comfort

    Comfort Well-Known Member Premium Member

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    And I even bring video.
     
  18. stevo

    stevo Backyard Farmer Premium Member GOLD

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    with all this fire pit stuff going on i must have one too, maybe just a simple brazier will do me.

    We have the occasional fire at the neighbours house, which prompted me to check the council regulations just out of interest. The rules state that you can only have a fire in your suburban yard if you intend to cook food with it. We cook jaffles :cheers:

    I think the rule is fair enough, and probably not enforced at all, but could be good to stop the odd person having fires that smoke the neighbours out all the time.

    But one issue is, commercially sold fire pits are very popular, but according to council rules you shouldn't be using them? (in the suburbs, Moreton Bay for example)
     
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  19. Comfort

    Comfort Well-Known Member Premium Member

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    We cooked marshmallows.... they are food !!!
     
  20. ClissAT

    ClissAT Valued Member Premium Member GOLD

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    On Last nights River Cottage Australia episode on SBS they built a wood fired pizza oven using termite mound clay. There is no chimney.
    There was a layer of cement & vermiculite inbetween the mud layers as well.
    There were some fire bricks used for the sides & normal bricks for the front & a big slab of concrete for the back.

    I noticed it had cracked when it was fired up the first time.
    Maybe it hadn't dried quite enough but filming constraints meant it had to be fired rather than let it dry longer.

    I took a photo of the TV screen!

    mud oven.jpg
     
    Last edited: Aug 3, 2017
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