Little House 12x18 - Slight 'wobble in beams'

[tom.czajkowski]

Hello,

We've recently started building the 12x18 Little House plan. Foundation is post and pier with 8" concrete piers (sono tubes as forms) sitting on a 16"x16" 6" deep footing at the bottom of each 4' hole (6 holes in total; three on each side).

Set in the top of each concrete pier is a galvanized steel Y-bracket, which holds the beam on the high corner of the building and holds 4x4 PT posts on the other 5 piers (of varying lengths to get the beams level).

At the top of the posts are galvanized steel braces that secure the top of each post to the beam. Nailed in with 10d nails.

THE (POTENTIAL) ISSUE:  All is level, but some of the piers (tubes with concrete) are a bit 'loose' in the ground.  We backfilled before filling the tubes and even added a bit of concrete (Quikrete) in the backfill for good measure, but what we have now are beams with a little play in them, perhaps a half an inch of lateral movement with the beam on one side and a little less on the other beam.

QUESTION:  When I put the floor joists on top of the beam (cantilevered) and nail them in, will that add enough structural integrity to resolve this issue?  In other words, reduce the slight wobble? I'm not sure if what I'm dealing with is somewhat normal at this stage of the project or if I've irreparably screwed something up.

Thanks for reading and for any advice.

Tom

[glenn-k]

I assume that the longer posts have the wobble but diagonal bracing from the bottom of the posts up to the joists and or beams should steady things up.  As the flooring is added it should get firmer, assuming the soil has the bearing strength to support the weight.  I assume you put your footings into clean holes in undisturbed native soil - no compaction issues.

Welcome to the forum.

[tom.czajkowski]

Glenn -- That is correct, the longer posts are the ones that seem to be creating the 'play' in the beam.  I haven't done any diagonal supports yet (to joists or beams), but I will as soon as possible.  That, with the subfloor, seems like it should solidify matters.
 
And the holes were freshly drilled with a rented two-man auger.  Soil is a bit sandy in north central Wisconsin, but I remain hopeful it won't cause any long-term stability issues.  I may build up some perimeter 'boxes' (homemade wooden forms) around the protruding portions of each concrete pier (they're above grade by about 8") and fill with gravel and concrete just to eliminate the loose-tooth problem.  Probably overkill, but I can't live with the idea of the place tumbling over someday!

Thanks for the advice and reassurance.  I/we have very little natural talent and certainly no experience for this building endeavor, but we're having fun!

Tom

[glenn-k]

No problem, Tom.  Hang out here and we can all learn together.

[jraabe]

It is always amazing how a house firms up as each layer is added. One of the magical mysteries of modern wood frame construction is the synergistic structural effects that come out of the sliced up parts of giant plants and little pieces of wire.