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flyboy 03-22-2010 10:32 AM

Pier Foundation Question
 
Background

My house sits on a hillside. The house is on stilts (6x6) which in turn sit on concrete piers. The piers are about 24" in dia. I was told by the builder that the concrete piers sit on and are pinned to ledge. The area around the house is all ledge and boulders. It is my understanding that the builder picked a spot where there was a depression in the ledge and back filled the depression with truckloads of sand after pouring the piers.

House was built ~2002

The site is a little unusual in that the ledge has very low permeability to water so there is tremendous runoff even though the soil (what little I have) is quite permeable and has no clay. Any water quickly saturates the sand around the house.

I had a structural engineer in to look at the house shortly after I bought it. He indicated that the piers were adequate in terms of size and spacing but sugested I hire someone with soils expertise if I wanted an opinion on the foundation. The only way to be sure of the pier depth below grade is to start digging. Based on the topography of the site, it is almost certain that the piers are not all the same depth below grade.

The Problem

It appears that one of the piers has shifted this winter. There is a visible slant to the top of one of the piers (on the order of 10 degrees). I am fairly certain that the slant was not present last fall. The post that the pier supports is still pretty close to plumb. None of the other piers are out of plumb enough to be noticeable. I used a level to check all the piers and this one is definitely less plumb than the others.

My Questions

1. How serious is this ?
2. What type of profesional should I be looking for to get a relaible long term solution ? Can a contractor handle this ? My previous experience with a structural engineer is that you really need to know what you want designed before engaging their serivces. I do not want to hire a structural engineed at $200/Hr to speculate about how deep my piers are and weather or not they need to be ripped out. Any advice on finding someone that is qualified to diagnose at a reasonable price would be much appreciated.
3. Any thoughs on what type of solutions I should be considering ? Long term, I will need to do some serious landscaping around the house regardless as there is quite a bit of errosion and the sand blows everywhere. I expect that I will need to raise the grade a bit and create teraces. If I am going to be doing foundation work, it would be best to integrate the foundation work with the landscape work.

flyboy 03-31-2010 09:43 PM

Photo of pier
 
1 Attachment(s)
This is the pier I described in the previous post. It is a little hard to see but the level in the photo has been shimmed so it is plumb. The top of the pier that it rests on is not quite plumb.

Aggie67 04-01-2010 10:39 AM

I don't want to freak you out, but that's the worst I've seen yet. Is that a wooden baseplate under the pier? Can you take some pics from 4 spots, 90 degrees apart? I'm dying to know how they attached the post to the pier.

Also, this is just a casual observation from the two pics, but if that concrete pier was once level and plumb, then it looks like the very bottom has slid and carried off a good ways. Were the wood posts ever attached to the center line of the concrete piers?

You need to have that checked. That's a mess.

flyboy 04-01-2010 11:25 AM

Yes, the post is indeed resting on a base made of a piece of pressure treated lumber.

The posts are attached to the concrete pier via a holddown. The hold down bolts to the 6x6 post with two 3/4 inch bolts (you can see these in the photo) and to the concrete pier via a 5/8 inch treaded rod embedded in the concerte. If you look at the next pier over in the background of the picture, you can see the holddown for this pier.

The posts were never centered on the piers. This is true of all the piers. I have seen no evidence that the bottom of the post has moved relative to the top of the pier.

As I mentioned in the original post, I did have a structural engineer look at the house after I bought it. He made some recomendations which I am trying to get implemented (I am a bit overwhelmed with the home improvement stuff right now). None of the changes he suggested are going to be helpful if the foundation piers are not sound.

Alex Damgaard 04-03-2010 12:20 AM

My first thoughts are that the pier may not have been poured level at the top when it was built. Why don't you get a cheap water level and scratch some points on all of the piers, take some elevation measurements and compare them with an elevation mark someplace else on your house. Check these elevations every six months and see if anything has changed.


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