Concrete pad question for new tub

[robmet1015]

I am preparing for a Hotspring Vista.  The owners manual states it should be 4 inches for the Vista and lone and behold the pad is only 3 inches...should I be concerned?  I live in PA and the ground is hard and lots of clay and heavy mud.  The pad is at least 12 to 15 years old and the house is 60 years old.  The tub will actually be sitting in-between two pads (centered)...each pad is 10' x 12'. 

The tub will be centered on top of these pads to center under my porch slant roof.

There is a slight grade for the drainage of water.

Should I be concerned in any way...THanks.

[sorebikr]

Not knowing anything about how the pad was constructed, its tough to say.  3"...is it reinforced?  Was the foundation laid properly (sand/gravel etc.)  Is it cracked?  Has it held a tub in the past? 

[robmet1015]

I would have to say there is no rebar and reinforcement.  Its tough to say.  The pads have been there for at least 12 years.  No cracks and it is great condition.  There use to be a car parked there in past for some time. There are roof 4x4 pillars in there as well. 

With my calulations ... if the tub is 9x8 feet, 72 sq feet.  The tub will weigh at most 6100lbs with fully loaded 500 gallons an 6 people worse case.  Tub weight 1000 lbs and 4100 lbs if 500 gallons of water used.  If the tub weight is evenly distributed over 72 sq feet the weight per sq foot would be 84 lbs.  I think I'll be fine but trying to find concrete spec for standard 3inch concrete has been tough.

[Chas]

I have put many of them on 3" slabs. For whatever reason, a "4 inch slab" seems to only be just over 3" around here. I guess they figure if a "2x4" can be 1 5/8 x 3 5/8 then anything goes.

I would be concerned about the joint between the two - be sure that it doesn't have a raise or bump next to it, which is common. Also be sure the two surfaces are parallel to one another - that they don't slope away from each other.

[robmet1015]

I have put many of them on 3" slabs. For whatever reason, a "4 inch slab" seems to only be just over 3" around here. I guess they figure if a "2x4" can be 1 5/8 x 3 5/8 then anything goes.

I would be concerned about the joint between the two - be sure that it doesn't have a raise or bump next to it, which is common. Also be sure the two surfaces are parallel to one another - that they don't slope away from each other.

Thanks Chas...The two pad do slope a tiny bit obviously for drainage.  Not much I would think.  Where the pads meet they are level.  

I plan on having HS dealer come out and evaluating...so I do not run into issues in future with warranty.  If I need to do something I'd like to be prepared.  

Would a rubber/plastic pad help a situation like this at all?

[Chas]

If the two slabs are as flat as one, I wouldn't worry about it.

I don't know if a rubber pad would do anything for you. The plastic pads - I'm assuming you are referring to



would help if there was a noticeable gap, change in grade, or bump next to the joint. Otherwise I don't know if it would be worth the trouble and money. If there is one or more of the things I mentioned above, you can also build a simple deck over it and shim and/or level that deck to give the tub a good flat surface. This doesn't have to be anything more than a simple set of boards glued down to the slab with shims as needed. I tend to call this 'building a pallet' to make it seem less intimidating. It does help with uneven gaps or slabs with more 'run' than you would like for your tub. They can be 2x6 laid flat, spaced 2 or 3 inches apart. Screw a 2x2 on the ends to hold them in place and make them look finished - glue them to the slab so they don't move during installation, and so the shims/blocks don't shift. Cut to the exact bottom of the tub, or leave enough hanging out as you desire.

HTH

[robmet1015]

If the two slabs are as flat as one, I wouldn't worry about it.

I don't know if a rubber pad would do anything for you. The plastic pads - I'm assuming you are referring to



would help if there was a noticeable gap, change in grade, or bump next to the joint. Otherwise I don't know if it would be worth the trouble and money. If there is one or more of the things I mentioned above, you can also build a simple deck over it and shim and/or level that deck to give the tub a good flat surface. This doesn't have to be anything more than a simple set of boards glued down to the slab with shims as needed. I tend to call this 'building a pallet' to make it seem less intimidating. It does help with uneven gaps or slabs with more 'run' than you would like for your tub. They can be 2x6 laid flat, spaced 2 or 3 inches apart. Screw a 2x2 on the ends to hold them in place and make them look finished - glue them to the slab so they don't move during installation, and so the shims/blocks don't shift. Cut to the exact bottom of the tub, or leave enough hanging out as you desire.

HTH

Thanks Chas...this does help a lot.  I am banking on the dealer...who is very knowledgable in this area...to make the call.  I do not think it would be too much to building the platform you describe if needed.  Would the 2x4 on the ends site around the edge of the tub or will it be flush with the side and the bottom of the tub sitting on it.  I guess I am trying to exactly visualize.

I'll try to upload a pic...

[sorebikr]

I have put many of them on 3" slabs. For whatever reason, a "4 inch slab" seems to only be just over 3" around here. I guess they figure if a "2x4" can be 1 5/8 x 3 5/8 then anything goes.

I would be concerned about the joint between the two - be sure that it doesn't have a raise or bump next to it, which is common. Also be sure the two surfaces are parallel to one another - that they don't slope away from each other.

Thanks Chas...The two pad do slope a tiny bit obviously for drainage.  Not much I would think.  Where the pads meet they are level.  

I plan on having HS dealer come out and evaluating...so I do not run into issues in future with warranty.  If I need to do something I'd like to be prepared.  

Would a rubber/plastic pad help a situation like this at all?

Something like these perhaps?

http://www.ezpads.com/