Deck footings failing

My home in Southern Ontario sits on a hill with an approximate 25 degree slope. The concrete footings supporting my second level deck are slipping out. What are some posible long term solutions to properly support the deck? It is not posible to access the area with heavy equipment.

 

Welcome to the forums.

Is the hill eroding or sliding on you? That's what needs to be addressed first, IMO.

 

Thanks Mitch, the footings and deck are 40 years old and it looks as though the hill has shifted a few inches over this time as well as the footings have sunk slightly. Nothing about the house or surrounding are has changed in 40 years so I don't know that I should be too concerned about erosion at this rate of movement but I have very little knowledge about these things. The house has not shown any signs of movement. The deck joists go right through the foundation wall and are tied in to the floor joists of the house.

Without knowing better I think I have these choices.
- Remove the deck (least favorable)
- Adjust the posts on the existing footings to better support the deck
- Pour new footings and move the posts
- Build a retaining wall and move the posts to be on top of the wall
- Build a retaining wall and pour new footings within the retaining wall

I don't know how far to go with this one, and if I should build a retaining wall what style of construction do I go with.

 

I'm wondering if soil or earth anchors are an option. Cheapest would be if they can be used to stabilize what you have existing. Worst case new footings may need to be created but earth anchors would tie them deep into the hill to help prevent creep in the future.

 

I agree with the others that your hill is slipping. The really bad news is that it won't be confined to just the deck supports but will undermine the integrity of the entire house. You need the services of a soils engineer at the least.

 

This is the most formidable deck building task we have in the mountains. As Furd says, you should call in a pro to look at it and offer suggestions. They won't be cheap.

We are required to pour continuous footings the length of the deck, 24" wide and a foot lower than the frost line. Sometimes this can be to a depth of 4'. That's a lot of concrete for deck footings, but totally necessary to keep the mountain from sliding out from under you. It will, without a doubt, undermine your house eventually, so the professional call out is almost required.

 

Furd: There are some other structures on the hill that are the same age but don't seem to be suffering the same issues. There is another deck where the footings are fine and a set of concrete stairs perpendicular to the slope of the hill. I think your right though, have a profesional who understands soil and erosion have a look at the area.

Dane: I like where your going with the soil anchors. What if I bury a concrete block between the house and existing footing then anchor the footing to this block using tension cables. Is this the sort of thing you mean?

 

Thanks for chiming in Chandler. Great advice. I'm going to seek out some specialists in my area.

 

Are you sure you actually have footings at the base of all columns? The only things I see are tall, slender concrete pedestals. They appear to be leaning in the downhill direction because of not being properly anchored into wider, thick footings underneath them (and below your frost line, which has to be deep).

 

I don't think anything you do near the surface like burying a block (dead man) will be sufficient and in your situation I think it could compromise your house. The sweet thing about soil anchors is they are installed quite deep to get into solid, stable soil that is not susceptible to surface creep. Like others have said. Someone with professional knowledge in this area could be your best bet. Instead of haphazardly trying things they could engineer a solution to work the first time.

 

BridgeMan I just assumed they were proper footings but I'm going to do some digging this evening to see what's down there. Hopefully you're right and their just improper footings to begin with.