Jun 11, 2007

Sinking Deck Syndrome - Seeking Solutions

(Toledo, OH) We built our deck about 12 years ago, pouring our heart, soul, and sweat into this two-level wooden masterpiece. Unfortunately, in the past two years there has been a noticeable sag in two of the external corners (farthest from the house).

I am hoping that a knowledgeable reader will offer suggestions on how best to rectify this sinking deck. At the moment, the worst of the corners has fallen about 10 degrees, which is enough to get me motivated and fix the problem.

My wife, the engineer, believes that if we dig a 2-3 foot deep cone-shaped hole around the posts, jack the deck up, and pour some cement, the deck will be stabilized. I, being the person in this relationship lacking any engineering qualifications whatsoever, believe that I need advice of an expert nature.

Left: My cheesy MS-Paint approximation of my wife's vision of deck stabilization

Or - if not expert advice - at least someone with some experience in these matters. Thus, if you have any thoughts whatsoever regarding the stabilization of sinking decks, feel free to weigh in with an opinion.

Also: my wife reads this blog, so be kind with any criticism. Hell hath no fury like an engineer scorned.



Anonymous said...

I'm not an engineer, but I play one on the internet. Before I'd devise the solution, I'd want to know why the deck is sinking. If you don't determine that and fix the problem, your solution may not be very lasting.

In my case, a sinking walkway was due to erosion under it -- the result of a badly-placed downspout. I had the trough placed under the walkway and that solved the problem.

LTLOP said...

Believe the wife, not because she is an engineer, but because she is your wife. After 12 years of Marriage I've learned no matter how right I am I am always wrong. Essentially you win either way, 1. If it works you can polish the apple for having such a smart wife 2. Or if it does not work you can say: This was your idea not mine, I wanted to find out why it was sinking first. C'mon Mike I can't keep giving you these lessons for free.

Hooda Thunkit said...


Some thoughts based on my limited, and incomplete engineering training but as an experienced builder of my own deck back in '88:

The gray portion (the concrete) should be inverted, wide at the bottom, narrow at the top and below the frost line, which used to be 36", but with global warming, experience tells me that it should maybe be more like 42".

The taper is not necessary and the deck would be sturdier if the pour wasn't tapered.

Get 3000 lb. plus concrete (3,500 or 4,000 is better) and have glass fibers mixed into the batch, you won't regret it.

If the post is too short, dig to the proper depth, suspend that corner of the deck where it needs to be, pour and work out the air bubbles with a piece of wood, effectively encapsulating the end of the post.

If you do decide to pour to ground level (recommended), round the top of the pour to shed water away from the post.

As you can tell, I watch way too much "This Old House" and "DIY" shows/reruns.

Good luck!

Oh, check this out with your wife first, just in case I've forgotten anything :-)

microdot said...

Yes, indeed, water and gravity, the backyard architects worse enemies.

The wood posts now are just in the bare earth? What are their condition after 12 years?

What is the soil like? Obviously as noted in Mr. Dunnit and anonymous's post drainage has a lot to do with it.

Wood should never sit directly in soil if you want it to last.

I think your solution of jacking the deck, pouring cement feet around the wood would probably last another 12 years at least if you don't have problems with rot.

I spend too much time digging drainage systems for my property...
thank goodness I'm on a hill!

Stephanie said...

As a wifely-type, I strongly recommend giving your wife's character the credit of not needing pandering, placating, patronizing statements from you.

That is the extent of my advice. As per the deck, I'd probably say, "Maybe it's supposed to do that." Mechanical proficiency is not in my skill set.


historymike said...

Good suggestions, all, and I thank you. I hope to report on progress in the next few weeks.

Clay said...


historymike said...


Nah, we like the house and the neighborhood too much, although moving might be in the cards after I finish my doctorate.

Them thar teachin' jobs are few and far between 'round here...

Anonymous said...

I always found that this helped me when fixing my deck http://howtofixstuff.blogspot.com/2012/01/how-to-build-deck.htmll