Deck issues

[Cooler]

My rear deck is elevated and they rest on (mostly) concrete filled steel posts.

The previous owner built a room addition on the 58 year old Douglas Fir deck. The first year I was in the house two of the deck's joists failed under the weight of the addition. I jacked up the deck and replaced the sistered-up 2" x 8" joists with a triple 2" x 8" joist. I also added a 6" x 6" pressure treated post under the joist for additional support. The post is 10 feet tall.

Last year the door to the room addition was binding and I had to jack up the joist about 3/8" to ease that binding.

All winter the door was fine, but a couple of weeks ago it started binding again.

Then we had 8 consecutive days of rain and the binding went away. So it is clear to me that moisture is the key hear.

Do you think it is because the post is drying out and is shrinking, or because the ground that it rests on is drying out and shrinking. We went down 24" with the concrete to avoid heaving.

I guess I could play a garden hose on the ground for a while to see if that resolves the issue.

Any other ideas?

Note: The concrete filled steel posts are not to code. I can use pressure treated or concrete pillars.

[Woodenfish]

IMHO, it's FUBAR... At this point you might want to seek the advice of an engineer to see if this addition can be saved with helical piles or if it should be dismantled.

[jlanciani]

Cooler said:

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...We went down 24" with the concrete to avoid heaving...

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In central MA 48" is the minimum depth for footings to get below the frost line. I'd have to guess New York would be about the same. This might not be your main problem but it is likely adding to it.

[Cooler]

I have fully rebuilt the original deck using pressure treated lumber (working piece by piece under the addition).

The deck cannot be replaced easily. There is a steep slope where the original posts are and code calls for the posts to be dug down so that they are 8' from the edge of the slope. I got prices of $3,500.00 per post (there are five posts), and I have had three deck guys decline to do the work. So I ended up doing it myself.

I'm not going to tear down the deck or the addition. I am going to figure out what is expanding and contracting and I will deal with that specific issue.

I mean if you have a toothache do you expect your dentist to say, "Lets pull all your teeth and give you a nice set of dentures"?? Or do you expect him to address the one tooth that is causing the paint?

[Cooler]

jlanciani said:

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[blockquote]Cooler said:

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...We went down 24" with the concrete to avoid heaving...

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In central MA 48" is the minimum depth for footings to get below the frost line. I'd have to guess New York would be about the same. This might not be your main problem but it is likely adding to it.

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[/blockquote]

I checked and 24" is what was required. At any rate I did not experience any heaving. I am only having moisture related shrinkage.

[CLETUS]

Cooler said:

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We went down 24" with the concrete to avoid heaving.

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Google says the frost depth for your location is 42" so unless you transposed your numbers. You'll keep having problems.

[Cooler]

CLETUS said:

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[blockquote]Cooler said:

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We went down 24" with the concrete to avoid heaving.

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Google says the frost depth for your location is 42" so unless you transposed your numbers. You'll keep having problems.

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[/blockquote]

No heaving problems so far. Just this issue in the warm dry weather. This post was an addition and was not included in the original deck. I guess I could remove it.

The original deck was built strangely; it is hard to criticize it as it stood from 1953 until 2003 with no issues. I replaced piece by piece over a period of several years. I added two posts under the addition that were not included in the original design. One is resting on a concrete pad that was poured contemporaneous to the building of the house (I have no idea what the footing is on that. The other is as described. If necessary I will change it out. I'd rather not though.

[CLETUS]

Cooler said:

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[blockquote]CLETUS said:

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[blockquote]Cooler said:

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We went down 24" with the concrete to avoid heaving.

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Google says the frost depth for your location is 42" so unless you transposed your numbers. You'll keep having problems.

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[/blockquote]

No heaving problems so far. Just this issue in the warm dry weather.

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[/blockquote]

Cooler said:

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All winter the door was fine, but a couple of weeks ago it started binding again.

Then we had 8 consecutive days of rain and the binding went away. So it is clear to me that moisture is the key hear.

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You've concluded it is caused by moisture. My contention is that is freezing, thawing, muddy then drying... regular seasonal movements. Either way, you're seeing it due to the shallow posts.

It's 2Beast's busy season, maybe you'll get lucky and he can chime in with some professional experience.

Anyway, good luck

[EatenByLimestone]

Are you in sand?

[MKepke]

I think you are on the light track to identifying the root cause.

IIRC S-dry lumber 8' long is estimated to shrink 1/8" as it dries. That plus some xpansion/contraction of the beam could give you >1/4" overall plus whatever the floor-joists are doing.

My suggestion to identify the root cause is take measurements during the bind/non-binding periods and compare.

For example, run a laser or a mason's line and a sensitive bubble level from the house foundation to a fixed spot on the post (use a nail or make a mark). Recheck when binding or not binding..if the bubble has moved, the post has grown or shrunk.

The beam and joists are easy to track using a tape measure.

I had a similar issue..a PO had built an addition with a totally inadequate foundation (piers). The tie-in at the roof was strong tho, so as the piers sank, you could see daylight under the sole-plates (the floor was separating from the walls).

I reframed the floor to fix the problem.

-Mark