HAMMERED??? WHY NOT SCREW?
By Rodney Appleby, New Business Manager
PART I: The stuff you can see and touch.
Often in the feasibility stage the pros and cons of bored piles vs timber piles vs UC piles vs pad foundation get weighed up and compared. Ultimately, the decisions we make have to work on a technical level… and then be economically viable.
Piling can literally be as easy as drilling a hole and filling it with concrete! But the times it’s not that easy (as in 99% of the time), if you’ve not done your homework, and you chose the wrong technique, you will be riding the horse of pain off into a lonely sunset.
Let’s say you had decided driven UC piles were the way to go… But did you consider screw piles? And why, or when, would a screw pile be a superior option?
A pipe compared to UC’s ($/m) – it’s relatively similar.
The key ingredient here is lead time! If you’re doing a big job, to keep the costs down, you’ll have to order from China, Indonesia, Korea… wherever… but the Contractor will always tag a 3 month lead time before they can start. If it’s a smaller job, then they might buy it from Fletcher EasySteel off the shelf, but then you’ll be paying a much higher rate.
Technically, the same thing applies to screw pile pipe…. unless you’re Piletech… Piletech holds between $2M-$3M worth of stock (both pipe and plate) in our yards so that we can turn on a dime, and get your project started – whilst keeping costs low because we bought in bulk some time ago.
Piletech Screw piles = less lead time + cost savings.
BIGGER PLANT = BIGGER $$$:
For small piles the plant will be similar. But deeper piles with larger loads require larger drop hammers and leader frames, or vibro-hammers, and a crawler crane. This means:
· More upfront costs – as crawler cranes cost between $10k-$30k to mobilise,
· Take 1 day to mobilise and 1 day to demobilise,
· Cost around $2-4k per day more than typical screw piling plant, (considering all site plant and labour).
· Reduce the area available on site, so no room to “swing the arms” safely, and thus…..
· Piling productivity will drop. We regularly install 10-20 piles a day to 24m, and would estimate being 20-30% quicker than similar length driven UC’s.
o Note: each day more = another $2-4k the client will have to pay for.
Cranes and leaders typically costs more per day than screw piling, with more “one-off” costs.
Crawler cranes and leaders? On a small site even turning becomes an issue.
Screw piling plant is smaller, quicker, nimbler, easier, and safer!!!
ENVIRONMENTAL & TMP:
Often contractors will pre-drill a starter hole to help stand the UC’s upright. If so, make sure you’ve allowed to handle the spoil, and cart it off site. Erosion and sediment control is a major with wet surfaces. It gets tracked out on to the road, and into drains. Silt fences, wheel washing (man + waterblaster), and traffic management all cost more money.
Contaminated spoil… new Work Safe H&S rules state the client, consultant and contractor need to be actively managing this. Tip fees, additional PPE, handling, cartage all cost more money.
If you don’t manage these the council shut your site down, with fines and even convictions!
Screw piles = no spoil = no ground water = no silt controls = no potential environmental incident.
Screw piles = no spoil = no unforeseen contamination variations = no H&S incidents.
Screw piles = less trucks + no spoil = no wheel-washing = less TMP $$ & no potential incident
Another potential hidden killer. Piling contractors often tag out of cutting the piles to height, and then welding nelson studs, or top plates on. At $200-$500 per pile – this will chew a hole in your profit if not allowed for.
Screw piles typically have a few bits of rebar coming out of the pile which are concreted in. No sweat, and allowed for in our costs.
Make sure you allow for connection costs when comparing apples and pears.
So hopefully by now you’re starting to get to thinking that you’ve got nothing to lose by asking Piletech to give a free Rough Order Cost to see if they’re within the ball park of my driven UC pile design.
Tune in soon for “Hammered? Why not Screw? Part II: The stuff you can’t touch...”