Would pier columns on slab footings with lintel beams be a good alternative for beam and block support if you're building on limestone?

[Boyblue]

All of the videos I've watched shows intermediate walls used to shorten beam spans with beam & block floors. If you were building on limestone as we do, would piers and beams be a cost effective alternative or would you suggest block walls (we don't use brick)?  When using pretensioned lintel beams 150mm x 200mm, how spread out would you suggest the piers be, to give solid support? Is 3 meters too much?  

[Roundtuit]

Why do you need block and beam if you have a slab?

[JohnMo]

1 hour ago, Boyblue said:

Is 3 meters too much

Ask your structural engineer?

[Conor]

Ultimately, the same loads will be applied to the ground, and need to be dealt with. So by changing from load spread out over a larger area, to point loads, may result in less digging, but those pads will end up with similar, if not larger quantities of concrete. Savings may be marginal, esp after you factor in re-design fees.

[Boyblue]

9 hours ago, Roundtuit said:

Why do you need block and beam if you have a slab?

1. Because we've torn down every available hill on our island to fill in slab foundations and according to one of the two suppliers left, we will run out in 5 years.

2. A lot of the remaining land is is low lying areas where even more fill will be needed than normal which will likely accelerate that eventuality.

3.  Occaisionally fill is hard to get and having an alternative is prudent, especially if you're trying to fill a housing shortage.

4. As fill becomes scarcer the price will increase. It has already gotten to a price where larger projects have begun barging in fill from nearby islands.

5. It’s really about sustainability vs convention.  There is a point where sustainable methods become more efficient than conventional methods and I believe we’re approaching that point.

8 hours ago, JohnMo said:

Ask your structural engineer?

Born in the 60's I have a good sense of how many minutes I must have in a cellular calling plan, however I don't have a clue of how much data I need.  It's the same with building materials and technology.  I have a good sense of what size a conventional steel reinforced column should be for a given situation however I'm not familiar with lintel beams reinforced with pretensioned wires.  I was just hoping someone here has the experiance.

8 hours ago, Conor said:

Ultimately, the same loads will be applied to the ground, and need to be dealt with. So by changing from load spread out over a larger area, to point loads, may result in less digging, but those pads will end up with similar, if not larger quantities of concrete. Savings may be marginal, esp after you factor in re-design fees.

1. With the use of pretensioned reinforcement for undergirding, along with beam and block, 20 - 35% less steel & concrete is needed, but with a higher cost of production, you could be right, the savings could be marginal. 

2. However, there would be significant savings on fill.  For example, for a 140 m2 home there would be a $3,500 savings on the needed 200yds of compacted fill for a standard 3 course installation.

3. The amount of labour needed is close, but there is an inverse requirement for skilled/unskilled labor. With the need for more unskilled labor and less skilled labor, there is a net saving with standard beam & block installation (1 meter floor height or less) and significantly more as height increases.

4. Although not a direct cost savings, there is about as week savings in time, for the aforementioned 140 m2 home.