Pizza Oven Patio - Retaining Wall Progress - April 2025

The last post I shared about the pizza oven was back in late March when I shared a photo showing the first four timbers being brought on-site and talked about I was in-the-middle of the excavation.  In that post, I laid out the next few steps (pasted below).  Since that post in late March, I've progressed through the first seven steps and the first part (the hard part) of Step 8. 

1. Clear back/sides down grade.
2. Dig out under timbers to drywell stone.
3. Lay out Fabric.
4. Lay down gravel + paver base to create level base for bottom timbers.
5. Start with the timber at the base of the slab, level it out and anchor in the ground with rebar.
6. Work around the timbers - anchoring them with rebar.
7. Stack additional timbers - attach with timberloks.
8. Backfill with gravel, drape the fabric over.
9. Back fill with earth.
10. Fill center with base + gravel.

As a reminder, we have a large, deep drywell under this part of the yard.  When I dug the slab foundation for the pizza oven, I excavated down to the drywell and placed the slab directly on top of it - no organic material between the slab and the large, solid drywell.  (The Drywell was installed in 2017 and has done all the settling it is ever going to do over the past seven-plus years.  

Following what I've learned on YouTube, there are three major factors to getting a small retaining wall like this one done correctly:  Proper excavation (deeper and wider than you would think), setting the first course level with proper prep work and using more gravel than you think you would *behind* the wall for drainage.  

After I excavated in all directions - and down to the drywell fabric, I laid my own fabric on top.  Non-woven landscape fabric. With enough out the edges to allow for it to 'fold over' on top of the gravel.  (more on that in a later post).  From there, I laid down some gravel and paver base to keep the fabric down.  And, began to pour in paver base to create the level I needed for the timbers.  

In this case, I had a level-goal:   I wanted the 6x6 timber that runs across the front of the oven to be level with the slab.  That meant that I needed to bring up a level grade to 5.5" of the top of the slab.  I went with bags of paver base - they were easier for me to haul.  I poured one bag after another.  Compacting them with a hand-compactor as I went.  

Once I was 5.5" shy of the top of the slab, I could set that first timber.  I used two, three-foot 1/2" rebar stakes to anchor the timber to the ground.  

That became the level for the remaining timbers. I started to build up the grade - using paver base - about four-to-five inches (compacted) of the timber on one side and set it in place.  In order to ensure that the whole thing is square, I only sunk ONE rebar stake into the timber (closest side to the originally set timber across the front of the oven).  

In the photo below, you can see that first timber secured in place along with the second timber (on the right of the photo) showing one rebar stake hanging out, not yet secured.  At this point, I had not set the other two timbers and still needed to bring up the grade via paver base.  

From there, I progressed to set the other, parallel timber.  I figured it was best to set the two 'sides' - leaving the 'end' for the last - to ensure square.  I used more than 30 bags of paver base underneath these four timbers.  But, that was needed to get them all level and square.  I finished the four base timbers with two rebar rods apiece.  Then, I began to dry-stack the second course.  

From what I've read (watched) about walls, having overlapping joints is critical.  Because I am using eight-foot-timbers and have the 'sides' outside (or butt'ing up against) the 'ends', that meant that I either needed an 8'11" timber or I would have to cut one down into two pieces.  

I don't know if you've ever tried to handle a 6x6x8 treated timber?  But, they're pretty heavy.  (At least for me).  So, thinking I could (easily) go grab a 6x6x10 treated timber, pop it in my car, bring it home, haul it out back and saw off a little over-a-foot seemed like it wasn't realistic.

That's why I took an eight-footer and cut it down to 53.5".   Leaving me with another segment that is 42.5" long.  Using two of those 53.5" pieces, I could create the second layer of the wall - with overlapping joints at the corners.  

Below, you can see the first course of timbers set (on paver base) and that first 53.5" half-piece stacked on top of the back of the wall.  And the 42.5" remaining piece stacked on one of the sides.    Once I did both sides, that completes my Step 7 (from the list above).

I grabbed a dozen Timberloks and sunk them into the timbers to connect them together.  Once that was done, I could begin to backfill the wall.  With gravel.  This is Step 8.  

I used bag-after-bag of gravel.  And filled in the area behind the wall.  18" deep (from wall to earth) and 18" high (from drywell to top of gravel).  And...remember...I excavated down to the drywell.  So, underneath this gravel is a 4' deep well of LARGE ROCKS SPECIFICALLY INSTALLED FOR DRAINAGE.  

See below for the retaining wall backfilled by way more gravel than I thought I would use.  I ended up going to the big box store four times for loads of gravel. 

Drainage is key for retaining walls.  And, my working theory here is that by 'connecting' this 18" deep of backfill gravel with the deep drywell (on three sides), any water that heads down towards the wall will drain first through this gravel and into...wait for it....the drywell.  Where it is carried out to the storm sewers.  

In the photo above, you can see the excess non-woven landscape fabric.  Nonwoven is the key part - it creates that 'separation barrier' between soil and gravel.  Which means, the gravel won't 'sink' and the soil won't 'mix' into the gravel to clog it up.  

Next up, finishing Step 8:  folding the fabric back on top of the gravel.  

Then, Step 9:  Backfilling on TOP of the fabric with some of the excavated soil and cover it all with mulch.  

Once that's done, we're going to say we're half-way done with 2025 Priority Project #2:  Make the Pizza Oven operational.  The other-half is water-proofing it with a small roof structure.  That's next on my list.