Post / Pier Foundation Longevity

[PFunk_Spock]

So in my brief house hunt I looked at a couple pre built cottages with a post and pier foundation. These were from the 60's and 70's and almost all had settlement issues of some form. Now, these were fixer properties as well, so that plays a role, but how much settlement occurs with these foundations over time. I dont think it would be to hard to remedy if you were living full time, but its a pretty big job in and of itself.

How have the post and pier foundations held up over time? If there is settlement, what do you do to fix it? How often?

[fishing_guy]

I would imagine it's like any foundation.  Follow the rules and you have a stable foundation which will far exceed the building above.  Cheat and you will pay the price in longevity.  Check around.  There are problems with "conventional" foundations as well.  Most of those problems are based on shortcuts as well.

I live in central Minnesota.  Footing depth is 4 feet.  The ramp I built on the front of the house is approaching 18 years.  It hasn't moved an inch.  But the footers are an honest 4 feet.

Our up-north property (Northern Minnesota) calls for 5 ft footings.  When we build, you better believe the footings will be all of 5 ft.  We will have no problems.

[NM_Shooter]

I have two main concerns of my concrete block "posts".

1)  I'm elevated above the ground a pretty good way on one end, and in a very windy spot.  I've braced with some 2" steel pipe, but I fear racking.

2)  My concrete blocks are exposed in an area that gets a lot of freeze/thaw cycles in the spring. I'm thinking I should put some sort of sealer on the blocks to keep them from freeze and water damage.  I haven't done this yet though, because I am aware that trapped moisture could also speed up the process. 

[rocking23nf]

my cabin is from 1965 and is on post/pier system, it has dropped around 2 inchs in 45 years.

[Don_P]

Check out silane/siloxane coatings for masonry, breathable but repel bulk water.

Piers have a heavier footprint than a continuous footing, the building weight is on fewer square inches of bearing. But, if the footing is correctly designed settlement should not happen. Notice the number of pier foundation repair companies though. Piers also don't do a good job transmitting lateral forces from wind or seismic from building to ground.

[rocking23nf]

i have a a-frame with 3 beams, the 2 beams on the bottoms of the A have sunk around 2 inchs in since 1965ish.

the middle beam doesnt appear to have moved.  right now the diffence is around 1/2 an inch, next summer im going to trim my middle posts by half an inch to compensate instead of raising 2 beams.

[John Raabe]

The advantage of the perimeter concrete foundation (crawlspace or basement) is that the wall and reinforced footing form an upside down "T" which is tied together with rebar and acts as a beam to span small settlements due to differential soils.

Of course, even reinforced basement walls can sometimes experience enough settlement to crack and require expensive repairs. Often these are caused by water issues or other soil problems.

The most important part of the foundation is making sure you have good solid, stable and well drained soil to support your footings. If you have this then you will have success with whatever foundation type you build. If, on the other hand, you have wet, boggy clay or mixtures of sand and silt and clay, and you can not dry the site out with a french drain or otherwise stabilize the site, then you will likely have problems of settlement, cracking, bowing or other movement - and a different foundation system won't change that.

Lot's of building sites exist... not all of them should have buildings on them.

My Article on 8 Tips for Planning a Country Homestead has been on this website for over 12 years. Use it to avoid the mistakes of others...

http://www.countryplans.com/landkit/tips.htm

Problems of foundation settlement are usually blamed on the foundation type or the way it was built. Often the real cause was soil that is not stable and wants to change shape and move around.