Hot Tub Suggestions Installed on Sloped Earth

[jukeboxpunk]

Hello and good day.

Let me first start by saying, I don't want this hot tub.My wife wants one and I am appeasing her by purchasing one and doing all the install work for the dang thing.

With that said, I have run into a crossroad and need some suggestions on how to approach a hot tub install on sloped terrain. 

Size of hot tub is 7 person and fully loaded with people weighs around 3 tons.

The picture I attached is where my wife and I would like to install this beast.  I don't want a concrete pad.

My two options are a retaining wall, back filled with crushed stone and pebble -or- 6-9 poured footings for a deck of some sort. I would rather do the backfilled retainingwall because it looks good when complete, i am just not sure 3 tons would stay compacted for long.

Any suggestions would greatly be appreciated.

 

[JacuzziJack]

Do you have a skid loader, or can you rent (use) one? Were you going to do this by hand or machine?

That slope, to me, doesn't look all too steep ....at least to my eye, in your picture. So, if I'm seeing it right, I think if it were me, what I think the easier route would be to go ahead with your idea of a small brick retaining wall on the lower end, and dig it down 12-14" on the high side (use that earth as fill on the lower side). By doing that, you have a lower amount of retaining wall and 1/2 or so of the H/T will be on firm ground on the upper side that won't settle. If you get a plate compactor from home depot or wherever, and pack it down a couple times as you build it up, you'll be fine. 3000 lbs over that amount of area isn't that much and if you have it half on old ground, you're talking 1500lbs over a spread out area -- not that much.  Just make sure you bank your retaining wall per best practices or use interlocking blocks, etc. Put gravel underneath. You'll want to plan it to allow enough space for someone to remove the panels and service it on all sides.

What you might consider is there are square plastic 'pads' that you can buy to put under a hot tub. They come in 2'x4' sizes and interlock. Besides making it a lot easier to build a base, they also help distribute the weight out and help keep the earth from 'spreading' outward. And helps keep rodents from getting in from under the H/T. Also you don't really need to deal with any gravel clean-up when you're done with it, so you save a bunch of work there ...just sell the pads and refill in the area. But you should put sand under the pads.

Let me first start by saying, I don't want this hot tub.My wife wants one and I am appeasing her by purchasing one and doing all the install work for the dang thing.

That almost ensures that you'll end up LOVING it a lot more than HER!!!    That's how it usually goes.

Good luck, show us the finished product too.

 

[jukeboxpunk]

Hey thank you for the reply Jack!

I will be doing this project for the most part by hand. Compacting would be done with a machine compactor. I bought 6x6 timbers for a timber retaining wall.  I can bank the timbers as well and place rebar down through them.

The slope from stake on the high end to the stake on the low end is level if the low end comes up 16" or the high end is lowered that much. I am most likely not going to dig into the earth do to the roots of the trees surrounding the area.  But I could back fill with crushed stone, and compact, then add pea gravel on top.

Does that sound right?

Hopefully I will love this tub once it is in.

 

[Tman122]

It matters where you live also. Do you have ground freeze in the winter?

 

[jukeboxpunk]

Tman yes we are in NH and have freezing periods.

Digging down may present a challenge do to ledge.

 

[bud16415]

For what it is worth my 2 cents is this. It sounds very nice and romantic to have a remote located tub in the woods. In the practical world you have to deal with snow and leaves. Sticks falling on the tub etc. You have a long underground run of a 220v line to the tub. Digging into a slope you will have leaves and mud building up on the high side against the tub. Depending on what tub you buy the bottoms are more susceptible to ground moisture entering the surround and causing problems.

The ideal location for a tub is a screened in deck / porch with a roof over it, but I get people want to be one with nature and the outdoors when in the tub.

I want my tub to have a view of nature, but I don’t want to have to walk and shovel my way to it in the winter. Then having to shovel a bunch of snow off the top to find the cover froze down. We love to use our tub on a snowy night or even in the rain. It is not any fun without some cover. We installed ours on a deck close to the house in the summer and loved watching the stars until the weather started to change. We then added the pergola with a roof.

Given your location I would suggest a deck for the tub with an elevated boardwalk from the house to the deck. You could run your power under the boardwalk and not have to bury the conduit. Build the deck large enough that when you want to add cover above you can attach that to the deck. Getting in and out you don’t want to be bringing in stuff from the ground stuck on your feet. Flip flops and such help some but never seem to do the job. 

I hope you learn to love your tub as most of us here do. I’m afraid though if your heart isn’t in it now when all the maintenance starts. Because even if you don’t use it you must keep an eye on it pretty much daily and 4 times a year drain and clean and fill it. The easier the access and the planning on setting it up the better that goes. It is easy to run the garden hose over in the summer and throw it in to refill it. in February it becomes a task. About once a month the filter needs cleaned etc. I put outside water hot & cold right next to the tub and I can rinse the filter out in the cold weather outside.

For me there is much more to location than getting a solid base.

Good luck and keep us posted on how it goes. 

 

[jukeboxpunk]

Thank you Bud!

The spot where I look to establish the base is literally 20ft from the house and the conduit run isnt too much of a deal for me.

You are right though about a stable foundation and cover. Maybe an overbuilt deck base is the way to go and later on if and when the wife asks for a roof of sorts I can add that.

My only concern with a deck is leveling it after it has sat for awhile.  Some had suggested using heavy bolts as pins to the beams, that way you can level the deck then shim in between the bolts once at the proper level. But something about 3 tons on 6 or 9 bolts leaves me concerned.

 

[jukeboxpunk]

Here is another angle of the site. So to the right is where this project is starting.
Not too far from the house.

Wiring and conduit will go under ground to the corner of the house where the spa panel will be located. Then main line will go into the eaves back to the main panel about 75 ft away. Pretty much a straight run.  I am not concerned at all with the power runs. just the structure this tub will reside on.

 

[Tman122]

So your high side is what needs to be cut down and a small wall built? That makes it easier and better, nothing but settled earth. Then leveled and filled with compacted #2 limestone. Then build a small base to set on top of the compacted limestone. Make the base out of treated 4x4's on 12" centers and 3/4 treated plywood. The largest span for the plywood will be about 9". No problem holding a tub. If it settles or heaves simply empty the tub and shim the wood base. The treated plywood base will last as long as the tub. You got the right tool there along with a shovel and a beer.

 

[bud16415]

My deck is 12 x 16 and 30” high the tub with water is around 6000 lbs and then another 1000 of people in the tub and another 1000 of people and stuff on the deck. I have 3 rows of 4 posts supporting the deck 4x4 posts sitting on the precast deck footings they sell at builder’s centers. All my posts are cross braced. 3 beams of doubled 2x8 and then 2x8 floor joists and 5/4 PT decking.

We live in northern pa and get 100 plus inches of snow per winter and temps down as low as -30. My deck has been holding fine for 3 years now. The one winter we had a frost more than 48” deep. If the deck is free standing it will move up and down just as your stone pad will. You are not worrying about a quarter inch tilt mid winter as it will come right back flat in the spring.

I ran the numbers on my posts and 4x4 are fine as long as they are short. The bigger 6x6 is needed for column strength on tall decks only 4x4 will carry the length.

We get a lot of wind and in the worst months I have some wind breaks I attach to the columns of the pergola. They extend up above the top of the tub about 24”. 2 sides of our tub are just a couple feet from walls of the house and that with the wind breaks makes for fun winter tubbing. Most people keep the water in the winter pretty hot 103-104 and even though it is cold out that temp water you need to get the top half of your body out of the water from time to time. The cool down seat is the one for doing that. If it is around freezing and some wind most people don’t like cooling down that fast. Blocking the wind helps a lot.   

 

[jukeboxpunk]

If I do a deck I will keep it small, probably no bigger than the tub and room for the steps.

I bought the 6x6 PT timbers already.  For the footings I will have to do 12" sonos.

Thinking about only doing 6 footings.

Just need to know my beam sizes and what to sister together.  2, 2x10s? 3, 2x10s?

 

[JacuzziJack]

Bud makes a good point. If you could put it closer to the house it will be better for a lot of reasons. I was thinking of suggesting the same thing.

It's been surveyed here and other places, those who tend to use their hot tub the most typically use them more in the winter (believe it or not??), and those who have their hot tub close to the house door use it more than further away ....not just the house, but preferably a few easy steps from the door. I know a guy who uses his hot tub all the time and he built a special deck for it and it's literally 2 steps from his back door and he's in.

So, if you don't mind moving it closer, maybe it'll make your landscaping easier and more useful to access the tub when it gets cold.

 

[Alan]

Bud makes a good point. If you could put it closer to the house it will be better for a lot of reasons. I was thinking of suggesting the same thing.

It's been surveyed here and other places, those who tend to use their hot tub the most typically use them more in the winter (believe it or not??), and those who have their hot tub close to the house door use it more than further away ....not just the house, but preferably a few easy steps from the door. I know a guy who uses his hot tub all the time and he built a special deck for it and it's literally 2 steps from his back door and he's in.

So, if you don't mind moving it closer, maybe it'll make your landscaping easier and more useful to access the tub when it gets cold.

I'm in complete agreement here.  We have owned a tub 14 years now.  Ohio Winters are cold, maybe not Arctic, but we have used our tub 12 months a year every year. Our surrounding is more urban, but out tub is 4 steps from the door, though I have to make 8 steps to get the cover open!

 

[JacuzziJack]

I guess looking again at your placement with those other pictures, not too far from the house, I'd probably lay a thin base of 3/4" clear stone (no fines) then large bricks  ...maybe 24x24 pavers on the stone base and cinder blocks on top to get your height. Then cover with whatever decorative covering you like. I don't think you need to pour anything. I'd want to give the possibility of water being able to 'flow' under if it got really wet out for a week.

Then run some sturdy steel (preferred) or wood stringers across the bottom or more bricks at the appropriate height to support the middle areas. The reason I would do something along this route is because it looks like that area between the corner of the house and the trees is trenched a little to produce a drainage channel for water to run away from the house and down the hill. You don't want to screw the drainage up and run into the possibility of future foundation damage or basement leaks. Keeping it somewhat 'open' underneath the hot tub, at least using bricks which water can run through and under will allow water to pass. If the H/T base becomes a little uneven after a couple years, just have someone come in with a bobcat and some long fork extensions and lift it out of there, then straighten or shim the base and set it back on. If you know a guy with a skid loader I'm sure he can do it.

Let us know how you come out

 

[jukeboxpunk]

Unfortunately I've gone the footing rout.

I have 2 and half footing holes dug thus far. I was able to get down 40-42". Now that I'm
Down that distance, I have about a foot of water accumulating in the holes on the low end.  This is surprising to me because I am on a few hundred foot high hill. I was expecting to run into ledge and had nothing but smooth shoveling all the way down.  Definitely clay like soil. I bought my tubes and trash bags, just have to get stone for the bottoms.

I have second guessed myself multiple times on this project just because of the weight of the tub.

As far as proximity to the house,  it is close to the house maybe not 4 steps away but 6-7 steps, less than 20 ft.

I would have loved to go the backfill rout but again back to second guessing myself.  But now that I'm down that path of footings I can either continue on or backfill holes and go the retaining wall rout.

Any recommendations on dealing with water table issues? We had lots of rain before I started digging.  Actually a lot of rain for NH where I'm at.  I'd like to be 48"down but the soil is so packed and dense my shovel is barely breaking it apart. 

 

[bud16415]

I outlined what I did in post 9. We live just inland of Lake Erie and have some of the coldest winter temps in the state. Two years ago it was 30 below for a week. The frost was really deep and we had issues with our porch and garage doors lifting because the frost got below the footings. On the other hand the 12x16 deck had no problems as it was supported only 6 inches below the surface but was designed to be free floating and not attached to the house. I built the deck 1 inch from the house and 3 inch step down from the door leading out. Out-swing door. The frost lifted the deck maybe an inch and in the spring it came back down. In your case a much smaller platform would work equally as well I think.

Soil is in a state of natural compaction unless it has been dug up in the last 10 years. I was careful when I dug down to keep the virgin soil flat and I did use a hand tamper when setting my post seats. I have them buried to ground level and the first freeze locks them in place solid. Then if the frost goes deeper they stay in location just move up and down. With this type of a deck you don’t rely on the posts for stability, it is all in the structure like your picnic table sitting out over winter. I could easily lift my deck and move it in one piece if I had a crane or something. People build them like this at campgrounds all the time and they hold up well. My power is going thru seal-tite so it will flex with a little movement.


With your footings and posts I never liked pouring right into water. Maybe you can bail your holes right before you pour or seal the ends of your tubes. 

 

[jukeboxpunk]

I have my 4 holes dug down to about 42" .  I also widened the bottoms out to about 16 inches and plan to do the garbage bag method of pouring the footings to get a wider base. Also now considering adding 2 more footings in the center. Currently the footings are 7' oc apart. 

The hot tub is a 7 person hot tub with a 7'7"x7'7" footprint. So it should overlap the footings once on top. The hot tub without people weighs about 5600 lbs. And to split that between only 4 footings seems a bit shy.

BTW water is dried up and gone, which I am happy about.

Ill post pics later

 

[bud16415]

To give you a feel for support my tub is 8x8 and 6000 pounds filled. Deck is 12x16  with 3 rows of 4 posts about a foot in from the sides. The tub sits in the corner more or less with access room on the one end for the cover lifter about 2 feet. But all the weight is over 2 of the 3 beams running the 16’ direction. 4 posts land under the tub is all and they are 4x4 about 20” long the 4 carry some weight thru the beam. I ran the column numbers and 4 posts that short were way more than enough.

I’m pretty sure your 4 piers you are pouring will be way more than you need. I would add rebar to them for the pour though.

What are you using for beams, joists  and decking. Will you be using hangers or stacking the joists over the beams?

 

[jukeboxpunk]

Going back and forth on using a post from the footings. If using a post ill probably use 6x6 notched for the beams. Beams will run parallel to the slope.

For the beams i was either going to triple up 2x8s or sistered 2x10s 10ft length. I would have a 1.5' cantilever all around, and it leaves me room should I want to add posts for something.  Tub will sit centered on deck so that each corner of tub is over footings.  The span between footing is only 7ft. tub is 7.4'x7.4'

For the joists i was planning on keeping it consistent with the beam size and maybe sister up some of the center joists. Also plan on adding blocking in between joists.

For decking I was going to with 2x6s. secured with Camo screw system. 

This deck wont be very high in the end. from ground level up to level is about 15-16" on sloped low end maybe less. I will either use a post or bring my concerete footing the height i need, then the opposite end will be either flush with footing or on a small post.  Trying not to exceed 30" height.

For steps for getting onto the deck I am going to get reclaimed granite curb. They sell it here cheap, being in the "granite state" afterall.   

 

[bud16415]

Triple 8’s or double 10’s will be plenty. So will 6x6 posts that short. 5/4 decking is more than enough but the 2x6 will work fine.

True PT posts made for below grade will outlast a couple hot tubs. I would hold the posts off the bottom of the holes about 6” and mix a bag or two of ready mix and dump in each hole. Back fill and compact as you go with a 4x4 post.