How high do your peirs stand off the ground

[brian_nj]

I have just about convinced myself to go with the pier foundation. But here is a question how high off the ground are people extending their piers? We have a lot with a bit of a slope so the front piers would need to be about 6' in height, while the back ones would only be about 2' we are turning the plan sideways so it is 32' across the front and only 20' deep. The piers should save me a lot of work but have not seen any mention of heights people have run them. We plan to do a 16" 8" thick footing with 8" concrete tubes extending one foot above grade. From that point is where we need the additional 6' Anyone see any problems with this?

[John_C]

Properly designed that wouldn't be a problem at all.

You're in the Johnson City, TN area, correct?  Drive over to Boone - Blowing Rock, NC  .....  you'll see lots of houses on extraordinarily tall piers, should give you ideas. 

[Redoverfarm]

Brian I think this is two fold.  One being what is necessary given the slope of the land to get the house off the ground so to speak.  Secondly what are you going to use the crawlspace for.  If additional storage such as mowers and the like.  If you are in a heavy snow region you wouldn't want 2-3' of snow laying against your rim joist or sidding for 3-4 months a year.  I am not sure of the maximum height that is allowed.  I would persnally extend the concrete 2' above grade and reinforce  with verticle and horizontal rebar.  Again it probably depends on the lot layout, how high you want your house to sit off the ground and any given special circumstances.

[diyfrank]

I though I seen a chart posted on here somewhere that showed  diameter/heights.
I'm sure someone has that info.

6' sound like its pushing what  8" can do.

Anything can be done. when in doubt, go larger.

How deep are your hole going to be?

Maybe key in to the hill a little deeper,  3' at least.

You need to hit bearing ground with the bottom of your holes.

[glenn kangiser]

We have them about 10 or 12 feet on the low side on 4x4's at a resort motel near here. Similar size to John' 20x30's.  They terminate on sono tube piers at the bottom.



Note that I am not saying I think this is great.... just that it has been there for a long time.

[MountainDon]

We had a similar situation with our cabin. Neither one of us really liked the thought of one end way above ground level.

Our solution was to move the ground.    We dug out the ground at the upper end on the slope and moved it downhill. We have a slight drainage slope now.



The beams have about a 12 inch clearance under them. Come summer, when the exterior siding is all finished we're thinking of using native rock to build a skirting around it. There would be a couple access hatches of some type.

[John Raabe]

"A safe rule of thumb is that a pier or post should not exceed 12 (for concrete) or 20 (wood) times its width in unsupported height." This is from my article on post and pier foundations: http://countryplans.com/foundation/index.html

An 8" dia concrete tube could thus go 96" or 8' tall using this rule of thumb.

If you are in hurricane or severe earthquake country check this with the inspector or an engineer.

[MaineRhino]

Ours are about 4-5' at the highest point, and less than 12" at the lowest. After this pic was taken we put on all of the bracing.



They sit on concrete or ledge.