Preparing A Foundation

[UnderTheStars]

Hi!  Just ordered my tub, planning the foundation.  I'm drawing plans for an 8' x 11'  deck, 12" high (next to an existing brick patio.)  But I'm also wondering about the "compacted gravel" approach.

Gravel w/some kind of pavers would be a lot easier than the deck but I'm concerned about frost heave.  I know that a thick enough compacted base will easily support the weight.  But compacted material is still "flexible" and it seems that when the ground freezes it would lift unevenly.

Any expert/engineer opinions on this?  Again, the gravel/stone/paver route is easier than deck or slab.  Also has the advantage of not adding height.  Thanks!

[stiffy]

Good Questions, and I have the same delema. and would like to add to this , I have been hearing from dealers that most perfer(if you are not going slab/deck/brick pavers) to use slag 3" to 4" deep.

SO, will the slag hold up to frost heave.

THanks U.T.S I did not even give frost heave a thought!

[Bill_Stevenson]

I am an engineer but this is outside of my area of expertise.  My advice to you is to talk to professionals in your area and see what they think.  I will say this, flexibility usually offers more advantages than rigidity when it comes to foundations and structures.  A young tree flexes and survives the hurricane, but the old oak is knocked over.  In an earthquake buildings that move survive, and rigid ones do not.  

With that as a premise, I would venture a guess that if you dig down deep enough to be below the frost line and lay a thick gravel bed in a uniform manner and power tamp it well, the foundation would be stable year round. It is also likely that if you do it properly, the difference in cost would be insignificant as compared to a concrete pad.

Regards,

Bill

[Ready2Buy1]

We just completed this process through a professionbal landscaper that we hired for this as part over our total project for our backyard.

We have 10" of 2A modified stone that was machine compacted (wet). Over that is 4" of EPA gravel that was machine compacted as well. We had our pavers (Belguard) laid over that base and our spa sitting on top of the pavers.

[Brewman]

I live in the cold upper regions of the USA (Minneapolis).
You'd have to put frost footings 48" deep to avoid the ground heave thing.  I know of several spa installs ranging from EZ pads on top of compacted sand or paver base, to concrete pads.  None of these have any frost heave problems.  
You paver base idea should work fine if done correctly.
Whatever base you install, be sure it will not void your warranty.
Brewman