OT. Is there a way to stop this?

[Tony]

Built this gate and fence in the summer of 2016. The gate was perfect. The posts are 6X6 treated timber set 4' in the ground with concrete.
The left post in the picture is moving. It's not movement in the ground, the post is set deep with 6 bags of concrete. It's movement in the exposed section of post. The post moves when it rains. It will raise the gate 1/2" higher. When the rain stops after several days it will go down level. Is there a way to stop this movement?

Before rain
https://goo.gl/photos/swNDAr4srrVfJVAC7

After rain
https://goo.gl/photos/pFLiAJ563NdRmZ3p7

[bobswire]

Looks like the left side bends (tilts) when it gets wet rather than rise (the grain flexing). It will eventually settle IMO. Leave it be it will find its place when completely dried,my guess is that some of the posts were still moist when you purchased it unless it was kiln dried.
You can alway plane it the fence later if need be.

[Black Dog]

If they were pressure treated then they have excess moisture from the mill. AS they dry they they can twist, warp, etc... If they are doing this with changes in moisture from outside they you need seal the end grain when the post in the position that you want it to be in so the moisture ingress/egress stops and the post will then stabilize. Since the tops of the posts are not capped this is the ingress point. How quickly does the post move post rain? Bob and I are both carpenters BTW and his plan will work too. Did you place a few inches of course gravel at the bottom of the post holes before you poured the concrete? Is the post lifting straight up or tilting towards the house?

[Tony]

If they were pressure treated then they have excess moisture from the mill. AS they dry they they can twist, warp, etc... If they are doing this with changes in moisture from outside they you need seal the end grain when the post in the position that you want it to be in so the moisture ingress/egress stops and the post will then stabilize. Since the tops of the posts are not capped this is the ingress point. How quickly does the post move post rain? Bob and I are both carpenters BTW and his plan will work too. Did you place a few inches of course gravel at the bottom of the post holes before you poured the concrete? Is the post lifting straight up or tilting towards the house?

The post moves quickly, raises and lowers the gate within 24 hours. Its only the left post. Both posts were very wet when I installed them. Months later in the summer months the left post that receives direct sunlight started moving.
I covered the post during rain several weeks ago and it did not move. I have an 8"x 8" cap on top of the post. I did not use gravel at the bottom of the post. The post is not lifting straight up, it's tilting towards the house with wet weather, lifting the gate and damaging the hardware on the other side. I have move the hardware several times back and forth, also shaved the top of the gate in a effort to make it level, just keeps moving.

[bobswire]

BTW both posts will eventually shrink (width wise)as they dry out fully. I wouldn't be messing with the hardware until they do (unless you are unable to open the fence. Other than that nice job.

[Black Dog]

BTW both posts will eventually shrink (width wise)as they dry out fully. I wouldn't be messing with the hardware until they do (unless you are unable to open the fence. Other than that nice job.

Bob is right. Let them dry out before moving hardware around willy nilly.

My advice is to permanently seal the open end grain on the top of the post. There are options to do this the best one would be to apply a water proof glue (Titebond 3 or a 2 part epoxy) to the end grain and let is soak in and reapply, then a permanent cap of some sort. The post dried out differentially on the sun side causing the movement. Every rain alters the moisture balance and cause movement. Wood fibres change length with differing moisture levels. Wood is a series of hollow parallel tubes that can quickly absorb and move water along their length, this is why you need to seal the openings at the top of the post. Seal it when it is exactly where you want it to be.

[donevwil]

My gate experiences a similar move every wet season, but moves back every spring or summer. In my case it's the expansive clay soil beneath my property, absorbs water and expands moving everything considered "fixed". When the soil dries out things move back, more or less. It's been so dry in recent years I'd forgotten how much things can move. This has been an extremely wet winter and with pretty much the entire Sacto/San Joaquin Valleys being river basin, flood plain or wetlands you're probably experiencing the same thing.

[Tony]

Thanks for the helpful recommendations! I will let it dry and return to level than seal the top with epoxy.

[wc1934]

I was told not to set the posts into the concrete. That the concrete should be poured first and dried and the posts installed on top on the hardened concrete. The concrete should be the footing and the post rests on top of it. (they sell concrete footing just for that purpose).
That's what I was told - but take it with a grain of salt.

[Tandem Rider]

In my experience, PT lumber does a hula dance for the first few years, sealing on all 6 sides slows it down and seems to keep the movement more restricted, hopefully within "limits" so the gate will operate ok until it settles down.

[simplemind]

FWIW, OP I think the ground (soil) is expanding, not the post or anything else. If you wanted to try experimenting by flooding water around the post during a "dry" period, that would probably tell you if that hypothesis is true. That doesn't answer your original question, but at least you'd know.
I always dug holes deeper than necessary and added gravel to the bottom of the hole, primarily to prevent rot, but it also provided a non-expanding base. Concrete was simply a ring around the post to keep it in place with the top graded away from the post.
I agree with the other "posters" (no pun), that there is little that you could do at this point and just wait for it to settle in.

[bluesea]

Six bags of pre-mixed concrete, where I live is maybe 3-4 cu ft, which would be inadequate for the applied use in this situation. I'm sure you used a lot more.

In what looks like a stable substrate (i.e. not overly sandy, gravelly, rocky), with the posts set at a 4' depth, I'd like to see the concrete something close to 24" wide for a depth close to 2' (tapering below).

[Tony]

I used six 90 lbs bags. I though at the time (as did my neighbor) was over kill.
Pretty sure it's not moving in the ground. I can take a strait edge and see the bending, towards and away from the house with wet and dry weather in the exposed post.

[bluesea]

I used six 90 lbs bags. I though at the time (as did my neighbor) was over kill.
Pretty sure it's not moving in the ground. I can take a strait edge and see the bending, towards and away from the house with wet and dry weather in the exposed post.



Roger that, the bags we have are usually 66lb.

[Hindmost]

This is fun (it's raining out now.)

The problem is that the 4x4 post on the left anchors the short piece of fence and when wet, the 6x6 post on the left heaves and is also pulled to the left. The 4x4 is next to the foundation and under the eave and does not heave as much as the 6x6's.