Concrete levelling agent

[wrainka]

Hi

I asked this question in another topic but didn't get many replies so moved it here so it may be less confusing.

We are waiting delivery of our first hot tub.I have a question about our concrete pad. We had a contractor come and pour the cement after we prepared the area with forms. In the days after with watering it down we noticed some definite low spots which concerned us. A level layed flat across the pad would show about 1/4" space underneath it. In talking with Jacuzzi they were very specifice the pad should be level. We got our contractor back and he recommended applying a top coat/skim coat type product that would fill in the low spots. He told us it will not bond permanantly here in our climate (we range from +30 to -30 C) but that it would be fine under the tub and would still provide support. The Jacuzzi dealer supports this idea as well. It seems our only option. The contractor couldn't guarantee if he took the pad out and started over that the next one would be level.

Any experience with products like he recommeded? How level are most areas spas sit on? is 1/4" something to worry about? I believe the dealer and don't want to jeopradize the warranty.

Would appreciate your thoughts.

[Jet Sitter]

wrainka - The leveling compounds you describe are commonly used for a variety of purposes.  Your contractor is being honest with you and if your dealer is on board you should be good to go.  The dealers here can give a more informed opinion about this issue and the tolerances for "flat".  You may ask the dealer if he will send you  a memo confirming that he agrees it will be an acceptable base, explaining that you are hoping to avoid a potentail warranty exclusion in the future.  The delaer may be true to his word, but what if he goes out of business, gets run over by a train etc.?

[dronning]

Leveling compond should work, just make certain they do the following before using the leveling compond.

• Clean the existing slab really well, I'd sweep it and blow it off with a leaf blower
• Apply a bonding agent (usually latex or polly based)

How long ago was the concrete poured?  The greener it is the better chance for a solid bond.

One question would be how long before you can put weight on it.


"The contractor couldn't guarantee if he took the pad out and started over that the next one would be level"  wrong contractor!!  Sorry if he does more than just an occasional slab he should be able to pour a slab the size needed for a spa to a dead flat surface or to whatever slope is required without dips.

[BNMac]

When we asked about the pad, our supplier stated that 1/8" per foot of slope was fine.  It didn't need to be absolutely level, in fact, having a bit of slope helps when there are dips in the surface.   

As dronning stated, however, if the contractor states there's no guarantee the pad will be level and flush, then it's the wrong contractor.  If the pad can have forms on 2 sides, a screed board can be used to level and surface the new concrete.  Else, an intermediate leveler board or some other method can be used - in short, a competent contractor or even an observant DIY'er can lay a flat pad.  Concrete shrinks ever so slightly as it cures but it doesn't dip a 1/4 inch in the thickness.

If you've got the room to add a couple three inches to the top of the pad to level it - add new forms and lay a new pad on top. If not, it looks like the leveling compound is your only choice.

Good Luck!