To Multi-Tech Products

Hello, I have a customer that needs to add more mechanical support under their spa to distribute the weight more uniformly, and reduce stress levels to prevent cracking.  It is out of the manufacturer’s warranty. What do you suggest?

Thanks,

Joe

To: Joe

The following picture shows a very nice aftermarket adjustable support added to an FRP Spa shell.

Feb 2015 download 016

The most important requirement for installing additional support is to prevent the new beam from puncturing the wall of the spa.  The method used to accomplish this is to install the beam so it transfers the weight to a strong metal plate between the beam and wall.  Please reference the picture above.

If there is a seat, step or flat area that would accept a support beam, and if it is accessible, remove any foam and expose the structure of the shell.

If you believe there is a plate and need to confirm, grind off the resin/glass to expose the plate for confirmation. The picture above shows an intended design and original equipment manufacturer (OEM) requirement. The plates were built-in at the factory at the time of manufacture. That is not going to be the case on every spa shell.

There is a wrong way to add support. One example is adding 2″ x 4″ wood stud material directly to the shell without a  plate.

IMG_0385

This is very bad practice since the large load of the spa will force the wood beam to eventually puncture the shell wall. I have seen this many times as a technician in the field. Even the nice support beam in the first picture above with its built-in,  top metal plate would pierce a normal spa wall without the addition of a strong weight distribution plate embedded in the structure or added in some alternative method.

Ideally, the best method would be a wood plate (as large as possible for the flat area). I would suggest a block of wood 2″ thick x 12″ x 12″ to start or as large as it can be while achieving good contact with the flat area. Be sure the plate sits flat against the spa structure.  Try to make it parallel to the spa base.  Use a 4″ x 4″ beam cut to size for the support. Be sure the 4″ x 4″ beam sits solidly on the deck, concrete pad or spa frame.  A plate may be necessary there as well.

IMG_0390

It would be best to secure the plate and support to the spa shell.   It should be done with Multi-Tech Products Polyester resin paste. Resin paste will provide about 30 to 40 minutes working time before it sets.  It is somewhat temperature dependent. In weather below 55 degrees, it may be necessary to apply heat after the application to cure the paste.

Grind the surface with 50-100 grit sandpaper to accept the Paste for good adhesion.

IMG_0420

Apply catalyzed paste to the plates prior to setting them in place.
IMG_0441

Secure the plate to the bottom of the spa with Resin Paste. Secure the beam to the bottom of the plate with the same “Paste”. The “Paste” can also be used to achieve maximum contact between the plate and the bottom surface of the spa structure where angle changes or uneven surfaces prevent full contact.  Good, wide area contact is needed to distribute the load.
IMG_0430

If the environment under the spa is frequently wet and the wood might eventually rot, use treated lumber, or the plate and the beam should be encased with resin and fiberglass prior to installing the beam and plate.  The following picture shows the wooden plate after encasing in fiberglass reinforced resin.

IMG_0447

 

 

 

 

 

 

If the spa needs to be lifted to insert the beam device, install the plate with paste, and allow it to set (cure).  Then lift the area up with a hydraulic jack (car jacks work, also).  Push the new beam into place (adjust beam length, if needed), retract the jack and allow the spa to set on the new beam.
IMG_0437

 

 

 

 

 

 

 

 

 

 

 

If additional supports are needed, repeat this process in order to distribute the total spa load throughout the spa.  One way to determine the need for additional support beams is to empty the spa, and put significant body weight in the unfilled spa shell.  If the shell moves, flexes, or the seats move downward with weight applied, this could indicate the need for additional under spa support.   This movement could would be due to either inadequate FRP reinforcement or insufficient mechanical support devices.  Properly distributed support is required to keep the spa shell from excessive downward movement due to the load derived from water and humans.  Pay close attention to the lip.  If a spa shell is built in a way to rely mostly on the edge support to provide the structure’s strength, the lip will move and deflect downward.  This would cause initial sagging and eventual cracking of the spa shell inner lip area.  Also, cracks inside the spa shell at upper corners could confirm inadequate supporting fixtures.  If the spa is within the manufacturers warranty, I would consult them before proceeding with an independent repair.  If it is not covered by warranty, good judgment must be used, but excessive movement begs for additional support to avoid problems.

Rob Clos

 

 

Advertisements