[MSteve]

I bought my first house last summer and there is a nice deck in the backyard. The problem is that one corner has sunk considerably since it was built, without measuring I will say 6 inches. Enough that you really notice the slope as you walk towards that corner.

My question is what is the best way to fix this?

The deck is about 3 feet off the ground, and the post is a 4x4 placed on a concrete block, sort of shaped like a pyramid with a slot on top for the 4x4 to be placed on.

I assume I would need some sort of jack to lift up the corner of the deck, and I'm not sure, maybe have some 4x4 handy and cut a new longer post and replace the existing one? Any suggestions are appreciated.

 

[Grampa Bud]

Has the concrete pyramid sunk in to the ground or has the 4x4 gotten all soft and squishy? You need to go back to where the deck is at the desired level or pitch and work from there. Drive a 16P into the edge of the deck where the level is good, stretch a string tight out to a stake some 4 feet beyond the end of the deck that you want to correct and hang a bubble level on the string at the stake. You may have several posts that need to raised. Small increments can be raised with steel shims under the 4x4. Larger lifts could be done with 2 foot square x 1+ inch thick concrete patio stones under the pyramid and steel shims under the 4x4's. Place a 6-10 ton bottle jack on a piece of 2x6 with a 2x4 on end from the top of the retracted bottle jack to a framing member about 3 feet from the post to be worked on and pump the deck up to your string level line. Fix your problem and move on.

 

[PaliBob]

Excellent advice from that old Grandpa guy.:wink:
How about posting a couple of pics?

It's easy just go to the 'How to...' post at the top of this page.
.

 

[MSteve]

I will probably take some pictures to post when I get home.

I'm not exactly sure of the cause for it to sink. I havn't touched the post, but I assume its not gone soft. The concrete blocks doesn't look sunken down, but I believe the ground around it may have eroded away a bit. This is because I recently noticed one of gutter drains ends right next to the sunken post.

So, placing extra concrete slabs underneath the existing one should be fine? This sounds easier than replacing the post, I also have some old concrete slabs I found buried in my yard.

So a regular car jack probably will not be sufficient? Otherwise I'd have to buy a new one, which isn't too bad, maybe $40. Also, how would I get concrete slabs under the pyramid base? It would be hard to lift in that tight space.

 

[Grampa Bud]

DON'T use a car jack. Most of them are not made for that kind of load. If you don't have a mekineck friend that has a bottle jack and you don't have any recurring need for one, go to a rental shop and pick one up for a couple of days. The patio stones I was refurring too can easily be obtained at any landscaping center and only weigh around 20# each. The pyramid may around 40-50#, but you can push them around fairly easily. If you move the block out of the way to put the patio squares in place and you can't get the block back under the post just jack the deck up a little higher and slide her into place.

 

[Gary in WA]

Take care of the water problem first, or it will be a continuing story. Extend or change the downspout deposit water away from the post area. Then fix the deck. Be safe, GBAR

 

[MSteve]

Here are pictures of the deck. Thanks again for all the advice. I can rent a bottle jack for $9 so I will probably do that. The only catch is I will have to put it on something because they only jack up about a foot. The pyramid block is actually smaller than I remembered so sliding concrete slabs underneath should not be a problem.

 

[txpatioslab]

I'd be interested to hear other comments after people see that picture, because it looks like an inadequately supported deck. I only see two supports, and I assume there are a few more, but that doesn't look nearly enough for the structure. You need to fix your current issue, and you might consider adding additional supports at the same time.

 

[Ron6519]

Does this deck have a ledger bolted to the house? Is it level?
You can use a scrap piece of 4x4 or 4x6 to put on the jack to reach the main beam. Just make sure the jack has a good base or the jack will go down, not raise the deck.
The support under the low part of the deck doesn't look like it has sunk. It could just be the guy who built it didn't have a level or was legally blind.
Ron

 

[MSteve]

There are 4 posts total. Three along the front and one in the center, and then the back is attached to the house. In the picture you see the center and the left/front post.

 

[Ron6519]

Is the ledger installed level?
Ron

 

[MSteve]

Yes, it is pretty level along the house so I think the ledger is fine.

It sinks a bit as you move away from the house, its possible it was always like this. But it sinks a lot more as you move towards the most sunken corner.

So this will be my process:
1) Find something stable to put under the jack to make it high enough
2) Place jack under the main beam that all the front posts are attached to (you can see this in the picture). About 3 feet to the inside of the outer post, which will be nearly between that and the middle post
3) Place piece of scrap wood on top of jack and raise deck to desired level.
4) Slide out current cement block
5) Slide in a couple of concrete slabs
6) Put current cement block back, may have to raise the deck a little further for this.
7) Lower deck

How does this sound? Any other safety precautions I should take? I'm not too concerned about everything being 'exactly' level, but close enough that it is not easily noticeable.

 

[MSteve]

An illustration