Tuesday 11 February 2014

DIY concrete retaining wall and patio

For several years a half dug out area underneath our sundeck has been an eyesore dubbed the "pit of despair".  Our sundeck is about 6 feet above ground with a support beam bringing the head clearance even lower.  We I decided at the time of building our sundeck that it would be great to dig down to get full 8 foot height and also allow for a "walk out" from our downstairs area. Tired of telling kids to stay out of the pit and explaining the situation to visitors, near the end of the summer I jumped down in the hole and resumed the digging that I abandoned several years prior.  I had thought only a few more wheelbarrows would do the job not realizing...well a lot of things.

Below you can see the beginning of the dig out.  I was able to find spots to deposit the dirt in all my various beds and also utilise the extra soil to build a grass couch (the grass couch will be featured in a future post).

The footings were poured and rebar tied together before Christmas.  We've been working the last month to put together the forms to make a 27" concrete retaining wall. 

Below you can see Shannon and Dad putting navvyjack and cement into our heirloom mixer.

It was a bit of an intense process as we had to work quickly so the mix wouldn't harden and there was also a risk that the forms could pop apart making for disaster.  Prior to pouring the concrete I was instructed to rub old olive oil on the inside walls, I'm told this was so the concrete didn't stick to forms but I'm pretty sure this is not standard procedure.  We rented an industrial concrete vibrator, which apparently if you don't use enough can result in empty craters in the wall, use too much and all the aggregate will sink to the bottom compromising concrete strength.  Yes, I did have to call various rental companies and ask if the had any vibrators available for the weekend.

My father in law and HHs dump concrete into the forms below. 

We had to wait to the following weekend to pop of the forms and see how the concrete cured. We're very pleased how the walls turned, the forms popped off without sticking and experienced only one major first aid incident.  The walls are smooth as a toddler's bottom, with just the right amount of air holes and Shannon's HH is walking despite the nail puncture wound to the foot.

Below is the completed retaining wall.  You can see that corten steel is embedded within the retaining wall to create the kick plate for the steps.  Corten steel is often used in exterior architecture and develops a nice rusty patina over time, it will also withstand the constant eroding drip from being beneath the drip line of the upper deck.

Thank you to all our extended family for all your hard work and expertise - we could not have done it without you.

Now all that is left to do is lay the paving stone floor/patio, landscape the surrounding area and decorating the newest addition to our yard. We'll also have to come up with a new name for under the sundeck as it will be "pit of despair" no more!


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  3. Wow amazing retaining wall! And that patio really brings a great look to the outdoor space. Nice job! www.sierravistaconcretecontractors.com

  4. Funny and very profound experiments. I never though anybody can do such interesting things with concrete.