Browse Forums Building Standards; Getting It Right! 1 Jan 19, 2011 8:29 am Hello We have a problem with our new house (3 years old) and I'm just looking to get a schooled up and understand why the builders soil engineer would have chosen bored piers. We have a timber frame Hardi Plank clad home of about 185 m2. We have terrible Biscay soils with a YS factor of 99. My understanding is that means from dry to wet the soil moves 99mm? Our house is 600mm off the ground and is supported by a series of cement blocks resting on top of 450mm dia 3000mm deep piers. There are approximately 75 piers. My understanding is that piers are bored to reach stable ground underneath. Other than the 600mm above the ground why are piers better than a slab? Cheers Tony Re: Why use bored piers over something else? 2Jan 20, 2011 2:33 pm The piers are suppose to be bored until they hit solid ground but from working for a builder who used screw piers, they just screwed and if it hit a rock, they just cut it off. Meaning they arent always in solid ground. They are also suppose to be tied into the mesh in your slab. One builder I work for actually makes the screw piers for builders and said he would never use them because they just rust out. The only reason they use them is because it's a cheap way on doing footings. Waffle pod slabs are another way, also cheap but I'd pick that over screw piers. Can't beat full concrete footings. Re: Why use bored piers over something else? 3Jan 20, 2011 3:20 pm Bored Piers are a reinforced concrete pier in the ground in my case 450mm dia and 3000mm deep. No relation to what you describe which sound like the things they use to save fence posts. Since I posted this question I have found that they use them for multi story city office blocks and the like, also when you have extremely reactive clay soils - we fit into the latter category. Apparently there are considered the optimum footing because once you concrete slab breaks you're stuffed. Also concrete slabs can sink or rise on one end or side. Cheers Re: Why use bored piers over something else? 4Feb 11, 2011 10:00 am If your soil is so reactive as you say, even with a slab you would still have needed piers to stabilize it and they would probably have been the same dept and diameter and maybe even the same number That sucks! Hope it all works out. Good to move away from steel anyway for all your reasons, but it's also thermally poor. 16 17889 How good is Simeon?! Always taking time to help others out! Wish we were building in NSW and could work together. Thanks for all that you do! 7 6577 DIY, Home Maintenance & Repair That’s very helpful information. Will find out more from there. Much appreciated. 11 13451 |