Digging Holes and Deck Foundations

Traditionally over the Christmas/New Year period the building industry shuts down, but for the owner builder it just provides some additional (paid) work free time for more building. Two deliveries arrived on 23 December just before the industry shutdown, the blue metal and the decking timber, readying us for our building holiday.

Structural and decking timber arrived from DIY Timbers Bomaderry

Some time ago in the schedule I had planned to build the decks over the Christmas/New year period.  The earlier assumption had been that the rest of the house would be finished and the decks would be the final piece of work. Needless to say the house was not done by Christmas and hold ups with the rendering meant that not even the inside was finished. The absence of completed accommodation meant that we were unable to invite friends down to assist with the decks and landscaping. Despite it not being the most ideal time in the schedule, as the external walls had not yet been rendered, the deck construction commenced.

There were three separate decks to build, with two of them turning a corner. All the decks were close to the ground being about 350 – 400mm off the ground so instead of using posts I planned to attach the bearers directly to post stirrups concreted into the ground. To try to keep the structural timber as high off the ground as I could I used 90 x 70mm laminated treated pine as bearers and 90 x 45mm treated pine joists. The decks were attached to the house with 90 x 45mm treated pine ledgers. These small timber sizes kept the depth of the timber shallow but necessitated more posts/stirrups.  

A well planned Christmas present of a Rotary Hammer drill was put to good use attaching the ledger boards to the concrete slab of the house with Dyna bolts. Although cheap the Ozito Rotary Hammer drill was very heavy to hold it drilled into the concrete easily, probably aided by the new unblunted drill bits it came with. The ten ledger board timbers, each requiring several dyna bolts, meant that the Rotary Hammer Drill more than paid for itself with the time it saved. 

Ledger boards installed and bearers being placed

 Not everyone takes a break in the New Year and my neighbour Gary informed us that the fencers would arrive on 2 January to put in the new fence. This meant that we had to remove the old fence before they arrived. Gary got out with the chainsaw cutting off the rails and we each took turns of the sledgehammer, somewhat therapeutically, bashing off the palings. The old hardwood timber fence was not wasted and Gary had arranged to redistribute it to friends and neighbours to use as firewood.

Therapeutic fence removal

 We hired a two person petrol driver post hole digger with a 330mm auger from Kennards in Nowra to dig the 35 post holes for the deck footings. We hired it on 31 December as 1 January was a public holiday we had to return it on 2 January and in effect got one day free. We had never used a post hole digger and despite brief instructions from Kennards we had great trouble getting it started. With some help from neighbour, Gary, the machine was finally stated. We started digging, thankfully Ben had control of the throttle as I had to use every muscle in my body to hold the beast of a machine and stop it from flinging me around in a circle. It was hard work. We had to keep lifting the auger out to shake off the soil. Then we hit solid clay and neither the machine nor I could go any further. The Alan Staines “The Deck Building Book” had suggested using 600mm deep concrete footings however, given that the engineering for the house concrete slab had only required the piers under the slab to go down to the undisturbed red clay layer, we figures that was good enough for the deck too.  

 

We started with the holes for the deck between the main and back pavilions. It was a hot day and the work was so hard that we only got through five holes in half a day. The soil was compacted and we hit patches of clay before we got to the solid clay layer. The work was extremely physically demanding then our spirits were crushed as we cracked through a storm water pipe that I had misjudges the location of. After this it was decided to dig two further holes, considered too close to the possible location of the storm water pipe, to risk using the auger on, by hand. Our work was thankfully put on hold by the need to join friends and a New Years Eve celebration.  Len Beckett, our fabulous plumber, came by and fixed our stormwater pipe on 3 January, in time for our conctrete to be poured on 6 January.

Cracked storm water pipe

Damaged pipe uncovered

With 27 holes left to dig on New Year’s Day we set ourselves a target of 10 before lunch, 10 after lunch and the remainder the following morning. However our technique improved, in particular in knowing how much soil could accumulate in the auger before we had to list it out and empty off the soil, as if left in too long the auger was almost impossible to lift and it take out too early it just wasted time and energy. We dug a number of tricky holes in awkward corners and close to the house, then got faster again as we moved to the front of the house where the soil was deeper before the clay was reached. As we moved away from the house to the holes for the larger front deck, where I presume the soil had not been compacted, the holes got easier to dig. We reached our target number of holes for the day and then kept going. With only 3 or 4 holes left there seemed no point leaving it to the following day and so finished all the holes. 

Holes dug

Post hole digger/auger in background

Although we had both worn gloves our hands paid a price for the assistance of the mechanical auger and we had blistered hands. I determined with a day like that on New Year’s Day every day for the rest of the year would be better than that day.  

Sore blistered hands

Meanwhile the fencers set to work on the new fence and despite the heat had the whole thing done in two days.

Posts and rails went in

The finished fence

With the concrete arriveing on 6 January, the first day back at work for the Ezyway mini concrete truck company, I had a couple of days to put in the post stirrups and bearers. The stirrups were attached straight to the bearers instead of posts and I levelled and propped the bearers up on chocks of timber so that the concrete could be poured straight into the holes. All was not smooth sailing, the difficulties we had with the post hole digger meant that some of the holes were not as accurate as thety could have been. This particularly caused a headache on the largest deck as the bearers had to be joined in the middle over a stirrup, which of course had to line up with a hole. A pep talk from neighbour Gary kept me going and helped me accept that stirrups not quite in the centre of the holes were not the end of the world.

Stirrups and bearers in place, ready for concrete

The deck starts to take shape

On 6 January the concrete arrived at 10am. I should probably have asked it to arrive earlier as it was a hot day and the concrete started to go off quickly before I could level it.  The truck driver from Ezyway was a deft hand at attaching and removing chutes from the truck and reversing it into just the rights spot so that the whole of the front deck was poured straight from the truck into the holes. We only had to wheel barrow the concrete into the holes for the decks around the back, saving us a lot of work. In the heat however, the concrete started to go off before I had time to level it and give it an incline down away from the stirrups, so the ones in the sun are a little lumpy. I should not hae worried, after all they will be underneath a deck!

Concrete in place

Temporary forms used to keep concrete contained