Woodworking Planshow to Woodworking Plans for Shell construction is one spa attribute that can vary greatly from manufacturer to manufacturer. To begin with all shells start with a top layer (approx 1/8” of an inch thick) which is typically made of cast acrylic. This top layer is impermeable to water and mostly serves an aesthetic purpose since it is available in many colors and textures.These acrylics are sold in industry standard foot prints like seven foot and eight foot sheets.
There are two main suppliers in the world that manufacture these acrylic sheets and sell them to the hot tub manufacturers. These companies are Lucite Acrylics and Aristech Acrylics. That is why when you visit one hot tub store to the next you see similar shell colors and textures.
The next thing about acrylic is color and texture. Color does not have any bearing on function, however, some hot tub manufacturers have what they consider “standard” colors and “upgraded” colors and that is because some acrylic sheets actually cost a manufacturer more than other colors. Some acrylic color blends take longer to produce or require more materials to achieve a certain look or finish.
Hot tub manufacturers pay more for these sheets and in turn so does the dealer and ultimately so do you (the end user). Another consideration when choosing your acrylic is texture.
Woodworking Planshow to Woodworking Plans for Acrylics come in smooth and rough finishes. Smooth finishes can be solid in color or swirled and provide a shiny, polished look. A rough finish can be solid in color or can have a speckled, granite like look. The advantage of a rough finish is that they don’t scratch easily and they aren’t as slippery.
The second layer can be summarized as a true quality difference between one manufacturer to the next because it’s the structural layer that provides most of the support. Most premium hot tub manufacturers apply a bonding resin behind the acrylic surface to make it tacky and spray several layers of chopped fiberglass to the back of the entire shell for structural support. This process can take a considerable amount of time as one layer must cure before applying the next.
Fiberglass backed shells don’t rely on the foam for structural support because the fiberglass, itself, is strong enough to support the pressure and weight of the water it contains. Another method of making a shell is to use ABS plastic backed acrylic. Instead of backing a normal cast acrylic sheet with a bonding agent and fiberglass this method backs the acrylic with ABS plastic (co-extruded).
The ABS plastic backing must then be further supported by heavy spray foams in or order to provide enough structural support to the vessel to withstand the constant pressure of the water it contains. Plastic backed acrylics are used often today because they lower labor, materials, and operating costs dramatically for manufacturers and because many steps are avoided in the manufacturing process.
Frame construction is also a consideration when shopping for a hot tub. There are three types of frames on the market, metal, plastic, and wood.
Metal frames are great in theory because of their strength and longevity, however, since the hot tub is a moist and continuously damp environment there is a high potential for rusting. Also the climate or the area of the country where you live can have an impact on the frame since humid or wet climates can also cause rusting and deterioration of the metal frame.
Plastic or PVC frames are also a seemingly low maintenance frame concept however they lack the structural integrity that is needed to support the filled weight of the spa over time and, therefore, have a higher propensity of cracking and failing.
Wood frames on the other hand have been used since the early days of hot tubs and are still the best. It is important that the entire wood frame in your hot tub is treated to avoid rotting. There are many manufacturers out there using untreated frames to reduce costs and some that just treat the 1 last update 2020/07/13 the base and not the vertical supports. Also keep in mind the heavier the frame the longer it will last. A 2” x 3” frame or heavier is recommended.Wood frames on the other hand have been used since the early days of hot tubs and are still the best. It is important that the entire wood frame in your hot tub is treated to avoid rotting. There are many manufacturers out there using untreated frames to reduce costs and some that just treat the base and not the vertical supports. Also keep in mind the heavier the frame the longer it will last. A 2” x 3” frame or heavier is recommended.
RECOMMENDATION: BUY A HOT TUB WITH A FIBERGLASS BACKED SHELL AND TREATED WOOD FRAME