Bricks, Masonry, Asphalt and Concrete - Concrete Slab For Home Spa

I want to pour a 8'x8' square concrete slab to place a home spa on. The spot I want to locate the slab on is sloped ground, maybe 5-10 degrees or so. The spa is rated at just over 4000 lbs wet, plus whatever people are in it. Once the spa is in place I will build decking around it to provide easy access.

I've looked at the DIY Building a Foundation article that describes building a foundation for a garage. Looks to me like I could adapt this for what I need, by pouring the four footing walls in a box formation, the sides tapered so the highest wall is at the lowest point on the slope, and all four sides level at the top. Then I could fill in the cavity with gravel, and pour the slab with appropriate reinforcement and according to local codes.

Having no experience with concrete other than setting fence posts with redi-mix, but being generally a handy DIY'er, is this a project I might tackle myself, or would I really be better off just getting a professional to do it?

Appreciate any feedback. Thanks!

What about frost for the footings?

If you really have a 10% slope and build on top of the ground, your downhill neighbor will enjoy his new spa.

Dick

Frost isn't a problem. I live in Seattle. But lots of rain could be a problem. Are you saying there is no way to set a slab level, on slightly sloped ground, and expect it to stay in place?

I can't speak to your specific situation but can tell you some things I've learned (and you very well may know these already). The guy that poured my pad didn't use gravel or rebar. Also he didn't backfill the one side of the pad and water got under there in winter and cracked it. Also the spa was set with only 3 days drying time.

the moral:

drainage is extremely important

rebar is a great idea

let the thing set up 28 days...it's worth it in the long run

oh yea, and no joints on a 12x12 pad either. I really got screwed.

as far as doing it yourself...just get a few estimates and see if your back is worth that. He did work hard even if he didn't do it right.

Its your call on the slope. - Strange things happen when soils get wet (California mudslids?).

You said you have 5 % to 10%. Last I checked, the maximum grade on a freeway was 7% to give you an idea.

Dick

I would get some help up front. At the least you'll need piers to support the downhill side. How many and how deep is something for the experts. The permit office can help you find somebody. Or you may need to dig into the hillside to create a level base. Either way, a mudslide is a concern anytime you build on a hill.

It never freezes in Seattle?