How To Fix A Deck That Has Risen and Now Slopes Toward House

by Milton Sommerfeld
(Stony Plain, AB)

I have a 10x10 upper deck held up by 2 pillars. these pillars have raised and the water runs toward the door. Would I be able to remove shorten the
pillars so the deck slants away from the house?

Editor's Comments

Your deck has risen because the footing at the end of the deck that support the columns or support posts for your beam have been lifted up by frost.

That is almost certainly what has happened and this would mean that the footings were not set deep enough. When you build a deck using an in ground footing the underside of it must be below the frost line and ideally the footing should have a bell shape to it.

What Happens When Frost Goes Below A Footing

If the underside of your footings are in the frost zone they get pushed up hydraulically by the immense force of the ice as water expands when it freezes. Ice will lift up almost anything given its power.

What happens is the entire footing is pushed up because of its very large surface area and when the ice melts away the cavity left behind under the footing is filled in with melt water and silt. When all is said and done the cavity is completely filled with compact silt.

Now there is no way that your footing is ever going to come back down again to its original position.

In The Future More Upward Movement Likely

And I hate to say it but if you get another year with a good freeze that is below the footing the same process will continue again and again.

Each year you could see your deck rise a little bit. Eventually it looks ridiculous.

Cutting The Posts

Shortening the posts this year to drop the end of the deck down and getting it to slope away from the house is only a temporary measure. The process will continue any year you have frost below your footing.

The Only Long Term Solution

What you have to do is jack up the beam so it is supported and remove the posts. Remove the footings and dig deeper. Dig at least a foot below what you consider to be your frost line.

Widen the hole at the bottom to create a bell shape. Pour the cement footing all over again. Re-install new support posts and connect them to the beam so the deck has the right slope away from the house. That is the only long term solution.

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May 12, 2020
Posts anchored not at grade
by: Anonymous

I also have a deck (built in Oct, 2019) that tilts slightly toward the house. I know this because since I have been unable to stain and seal the kdat-wood-flooring deck, it's been covered with a tarp for the past 7 months to protect it and keep water from pooling around the posts on top of the footers.

The kdat wood swells up if it gets wet so there is no gap between the boards.

There were many problems with communication with the company I used, and among the issues that resulted was that the posts are anchored to footers BELOW the grade (at least a foot).

I had not wanted any soil to post contact..had expected the anchors to rest on footers that were at the grade..and did not let the contractor back fill with soil.

Now, every time it rains, water fills on top of the footers (that are bowl-shaped so that the water doesn't drain away) and sits in a pool, surrounded by the clay soil, and in the case of one post, just two feet away from the foundation. I have to bail the water out from around this footer or it will sit there for days..or possibly weeks.

The contractor last fall had agreed to come back in the spring to cut the posts and install concrete piers.

Now I'm worried that the footers, at least the ones furthest from the house, will need to redone so that frost heave doesn't happen. Any advice about this situation?

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