Round Wooden Hot Tub Assembly Instructions


Unlike others, our hot tubs are manufactured with perfect computerized accuracy and require absolutely no on-site milling or cutting of the final stave. Each tub fits together perfectly and assembles quite easily in an average time of 1 hour give or take.


*Please note, the following assembly procedure is a slightly condensed version of the actual included instructions. Various size hot tubs of various types of wood may have slightly different instructions and ONLY the actual instructions included with the hot tub should be followed.


Important Note – Please read through the entire procedure of the manual that comes with your tub carefully before beginning the first step.*

Round Wooden Hot Tub Assembly Instructions

To assure a long-lived and structurally safe tub, a properly designed foundation is essential! To withstand the weight of the tub and water we recommend a minimum 4″ thick reinforced concrete pad. If you have any questions, please contact us for proper and adequate site preparation.*


Step 1: Installing the Suctions


Place the chine joists on the concrete pad so that they are 5½” tall and arranged as shown in Figure 1. Check the chine joists with a level and make any necessary adjustments. Next, put the three dowel pins in one half of the bottom and place the bottom-half on top of the chine joists. Be sure the side of the bottom that is nicely sanded is the side that faces up.


On average, both suctions fittings are located on the stave wall of the tub (3’ apart) after tub assembly.

If you plan to put one or two suctions in the floor of the tub, it is easiest done before the tub is assembled. If BOTH suctions are being installed in the floor (Figure 1), they should be separated by at least 3′.


Be sure the location of the suctions does not interfere with the chine joists and be sure the holes are drilled wholly on one board. The suctions require a 2½” hole. If you use a hole saw you will have to drill from both sides of the board. This will eliminate any tear out from the bottom side.


To install the suctions, first slide the gasket on to the through-wall fitting. Then apply five wraps to Teflon tape to the ½ inch end thread of the thru-wall(s). DO NOT apply silicone to the thru wall flange with gasket. Next, slip the male threaded thru-wall fitting into one of the holes.


Apply a bead of silicone to the flange of the straight nut.  Screw the female threaded nut onto the thru-wall body. Be careful not to over tighten the nut; snug hand tightening should suffice. (If the nut is screwed onto the through-wall too tightly, the swelling of the wood when it gets saturated may crack the flange, leading to leakage. Repeat these assembly steps for the other suction. At this point it is advisable to complete any other plumbing that occurs underneath the tub with a street 90 PVC fitting and an 8 – 10” – 1.5” rigid PVC pipe length.

STEP 2: Assembling the Base

Put the other half of the bottom on the chine joists and then slide the two bottom halves together, pushing them together as tightly as possible. Note that the bottom boards are placed perpendicular to the chine joists as shown in Figure 1.


After the bottom is in place the two plywood strips supplied with the hot tub must be screwed down across the seam of the bottom halves. Place the strips about 3″ in from either end of the perimeter of the tub. Use four 1″ screws to secure each strip. Remove these strips after the hot tub is fully assembled.


*Please Note: Failure to use the plywood strips will cause trouble in later procedures.

STEP 3: Fitting the Staves to the Base


Each stave must be properly positioned between the alignment marks located around the perimeter of the floor tongue. You will note that in Figure 2, the side of the stave that has a tongue is centered directly on the alignment marks. The side of the stave that has a groove does not line up perfectly on center of the alignment mark.


All the staves go on in this fashion. There can be gaps between every stave put on the tub. Do not worry about these gaps and do not drive the staves on with a mallet. The staves may be lightly tapped on with enough force to keep them from falling off. Once all of the staves are on, the tub is ready for the bottom, middle and top band (hoops).


STEP 4: Applying and Tightening the Bands

Figure 3 shows the bottom band at 43 3/8″ down from the top. Once all the staves are positioned onto the bottom, lower* the bottom band over the top of the tub and into position as shown in Figure 3, use 4 to 6 screws or nails to hold the bottom band in position (this may not be necessary on conical tubs that have notches for the bands).


This process is best performed by two people. The middle band is tightened first and then the top band is tightened second (Figure 6).  The lugs should be staggered with no two lugs resting on the same stave joint, but all in the same area as to hopefully hide them from view.

WARNING: Do not drive the band support nails more than ½” into the wood!  After the middle band is tightened at approximately 75%, lower the top band into place and tighten the top band to about 75%.


The staves will be pulled in and onto the floor tongue with minimal stave joint gaps.  If you have irregular stave gap joints, you can use a rubber mallet to GENTLY TAP the staves outward, on the inside of the tub near the bottom, to even out all of the stave gap joints.


Once the joints are all similar, then the bottom band can be tightened as described below ** (Fig. 3).  Go around the tub with a tape measure and check the height of the band.  Once the band is properly leveled, you may begin to tighten the band.  Two people best perform this process.


Try to avoid stripping the nuts from over tightening. While one person tightens the band lug, the other person strikes the band on outside of the tub with a dead blow rubber mallet (provide with each tub).  The object is to drive the boards on evenly all around the tub.  It usually takes 4 or 5 times around the tub to accomplish this.


STEP 5: Finishing the Tank Top Rim

Go around the top rim of the tank with either a belt sander to level the top edge. Finally, round off the inside and outside edges of the top rim, using a router with a quarter-round-over bit.  We now offer a wood Capping that eliminates finishing the top rim


Installing the Bench

Follow the procedures outlined below to install the 2018 Bench in your tub. All necessary parts have been provided, including hardware and Extended Star Drive #10 Bit.

Other Tools required include:  a variable speed electric drill, a #2 Phillips head driver bit, a #10 pilot bit (or 1/8” drill bit and countersink bit), measuring tape, torpedo or regular Level, and possible Skill Saw or Miter Saw.


The easiest way to determine where your Corbels will be attached to the tub is:

to dry fit the full circular bench on the floor inside the tub.  Align the first joint of the section in the middle of the stave where your first Corbel will be attached to the tub wall.  There will be an approximate ½”+- gap between the inside of the tub wall and the outside perimeter of the bench.  Align the outside circle of the bench sections together all the way around.  Now mark on the stave where the center of each Corbel will be located on that Corbel’s stave(s).  (The Corbels may split stave(s)).

Knowing the finished bench height, NOW you need to determine the height placement of Corbel in relationship to the bench section thickness. 


The Corbels provided have been precut for a Red or Yellow Cedar tub for easy installation of a 17” Height bench off the floor (25-1/2” measured down from the top of the tub (without Capping)).  NOTE:  Teak Benches are 1-1/2” thick and will require the Corbel to be adjusted ½” higher off the floor for a 17” Finished Height. 

If your DESIRED bench height is higher or lower, raise or lower the corbel appropriately.  Note:  If you are installing the bench lower than 17” off the floor, then you will need to cut off a portion of the long side of the Corbel appropriately to allow the finished lower bench height. (pic 4 oval circle)


Ensure you measure the thickness of the bench section (Pic 3) at the area where the bench section sits upon the Corbel (Pic 4 top red oval).  If you are setting your bench height at a different height than 17” off the floor, place the Corbel against the stave wall (Pic 4), place a torpedo level on the top of the Corbel (Pic 5), and move the Corbel up or down to located it level at the proper height, to be able to place the bench upon it, for the finished bench height you want.

Note:  If you are installing the bench lower than 17” off the floor, then you will need to cut off the long side of the Corbel appropriately to allow the finished lower bench height.


{{{Finished bench height, minus the bench thickness (Pic 3 or 4), equals the height of the Corbel placement against the wall.}}}


The orientation of the Corbel should be with the long side of corbel placed vertically against the stave wall and Short side 90* of the Corbel orientated horizontally for fastening to the bench sections (Pic 4).  Predrill your Corbels as shown in Pics 6 & 7 with a drill bit & countersink bit.  (Pic 6 shows a toenailed /angled predrilled and countersunk holes, Pic 7 shows a straight hole countersunk)

Refer to 6 unlabeled Pics below for next instructions     (last page for 3’ Height tubs)

Place one 2” Stainless Steel Screw (supplied) into one of the top predrilled holes of the Corbel and screw the Corbel into the stave wall.  Using a level, make sure the top side of the corbel is level.  Once two Corbels have been affixed with one screw, place a bench section upon both Corbels to verify the finished bench height and the bench ends (joints) are in the center of the horizontal Corbels respectively.  If proper, continue with using three 2” Stainless Steel Screws in the remaining three predrilled holes of these two corbels.  Continue with the installation instructions…

NOTE:   If installing a two tiered/split level bench, check your measurements and where the joint of two different Bench section heights would use the same Corbel, two Corbels will need to be installed next to each other.  This is where the Corbels will split two staves for each bench height.


…Now locate your third corbel on the stave wall and using the next bench section onto the 2nd & 3rd Corbels, with the first bench section still in place.  Verify your bench orientation and continue with installing the next Corbel in the same manor, using these two bench sections leap frogging as you continue around the tub until all the corbels are installed and you are back at your beginning point.


Now that all the Corbels are installed and orientated to be flush with the bench section bottoms, begin placing the Bench sections upon the Corbels for permanent installation.

Installation of the Bench sections begins with gathering all the sections, so they can be placed upon the Corbels and then adjust for spacing and orientation.  Note:  there should be a 1/8” gap between each bench section at the joint, matching the 1/8” gap between the three slats of each bench section.  The gap around the outside of the bench against the wall can be between ½” and ¾”.


With all the bench sections orientated how you want them, begin screwing down the bench sections using the extended Star Drive #10 Bit & the #10 – 2” Stainless Steel Screws.  Locate the screws approx. three quarters to one inch (3/4” – 1”) away from the joint on either side, as shown in (pic 13, 14 & 15).

As shown in Pictures, place one screw in each of the four gaps (above the Corbel below to be screwed into).  In the gap between the three slats, use the long Star Drive Bit provided, screw down and in between the gap, until the screw head is flush with the ¾” board, 1-1/2” below the surface top of the bench (Pic 3).       See Note below for Split Level Bench configuration.

NOTE:  IF two tiered / split level bench is being installed:

Please check to ensure you are screwing into the Corbel below.  The screw placement will change slightly to ensure the bench sections are screwed into the individual Corbels below respectively where the two different height bench come together. 

Installation Preparation & Services

Proper hot tub installation preparation requires that you arrange for the following three items prior to installation.

  1. Proper Electrical Circuit
  2. Proper Sized Gas Line
  3. Cement Pads/Foundations for Hot Tub & Equipment

The following are the suggested specifications for installing an ACC controlled Hot Tub System.

Electrical Specifications
-20-amp 240v dedicated service for equipment with gas heater. – 20-amp 245v GFI breaker (for Controller; Gas heater; Pump; Ionizer) – (total amp draw = 9 – 10 Amps).
-40 Amp, 240volt dedicated service for equipment with 5.5kW electric heater. – 40-amp 245v GFI breaker (for Controller with 5.5kW electric heater; Pump; Ionizer) – (total amp draw = 31 – 33 Amps).
-60 Amp, 240volt dedicated service for equipment with 11kW Electric heater. – 60-amp 245v GFI breaker (for Controller with 11kW electric heater; Pump; Ionizer) – (total amp draw = 51 – 53 Amps).
-The dedicated electrical service requires a neutral wire, run in compliance with National Electric and/or Local building code, with enclosure for breakers at the equipment location.
-Electrical Services are required by National Electric Code (NEC) to be GFCI protected.
-If 2nd pump purchased, please contact us for appropriate breaker size for your system.

Gas Line Specifications
Our gas heater requires a gas line sufficient to supply 125k Btu’s of gas, run in compliance with National and/or Local building codes. Note: If an upgraded BTU gas heater is purchased, check with your plumber to ensure a properly sized gas line is installed.

PVC Plumbing Recommendation
If the length of run (distance) between the tub and equipment locations is five feet (5’) and up to fifty feet (50’), Sch 40 – 2” PVC is recommended for the two lines In-fluent (from tub to equipment) and ex-fluent (from equipment back to tub jets/returns). Trenching of plumbing may be applicable. For runs longer than fifty feet (50’), please consult with a licensed Spa or Pool professional.

Spa Side Control Recommendation
The Spa Side Control comes with a 20’ ribbon cable (longer upon request if needed) with male (PCB) and female (WiFi) connectors. If there is more than 5’ between the tub and your equipment, you will need to run electrical Grey 1-1/4” PVC conduit for fishing the ribbon cable through to protect it from burial effects or other environmental factors.

Cement Pad/Foundation Requirements for Tub & Equipment

As we mentioned earlier in the “Locating Your Tub and Equipment” section, you will need a concrete pad or foundations for the hot tub and a concrete pad or foundation for the hot tub equipment.

Our basic equipment package requires a concrete pad of 24″ by 54″, although it can be squeezed into a slightly smaller area if absolutely necessary.

If you must use a slightly smaller area, we recommend that you wait until you have the equipment in your possession prior to pouring your concrete pad.

The hot tub itself also requires a concrete pad or foundation to sit on. For stability and settling purposes, the tub itself should sit on a single solid concrete surface. Everything settles over time and just like the concrete slab under most homes, concrete settles but remains flat.

Tubs have successfully been installed on blocks, in gravel or on pier block foundations, but the settling process is much more likely to be uneven.

An uneven settling process can concentrate the stress on a single area of the tub causing premature cracks and leaks.

The minimum thickness safety requirement for a basic hot tub pad is 4″ thick reinforced concrete with a diameter of 6″ less than the diameter of the bottom of the tub. Therefore, a 5′ round straight sided wood hot tub would require a 4′ 6″ square pad.

The type of ground underneath the pad should be stable as well. If the soil has a propensity for expanding and contracting due to extreme freezing or scorching temperatures, you may be required to add concrete footings to stabilize the pad. Checking with a local contractor is an easy way to find out whether you need footings or not.

Sunken or semi-buried tubs have also become very popular and they are much easier to get in and out of.

A wooden hot tub easily be installed below grade with a few minor adjustments.

You will need to dig a pit large enough to accommodate the size of the concrete pad and build a retaining wall around the pad to keep excess dirt and debris from eroding and coming into contact with the tub itself. The retaining wall should be made of concrete, concrete block or ‘ground contact’ rated pressure treated wood.

Please make sure that you leave a minimum clearance of 12″, preferred clearance is 24″-36″, around the entire tub; a 5′ diameter tub requires a 7′ wide hole. This clearance allows you to pre-assemble the tub above the pit and then lower it into place.

Tub assembly requires a minimum of 24″ of total clearance around it for proper construction. You may also want to consider adding a sump pump in the pit depending on drainage and ground water.

Installing a hot tub on or in an existing deck is also quite popular, but most decks aren’t constructed to accommodate the weight of hot tub filled with water.

An average hot tub filled with water weighs in excess of 5000 lbs. before you and your friends jump in and we strongly advise hot tub owners considering tub installations on existing decking to check with a licensed engineer prior to beginning tub installation.

Hot Tub Location Guidelines

Hot Tub Location Guidelines

The most important part of any hot tub installation is proper planning and the first two steps of the planning process are deciding the ideal location for your hot tub and your hot tub equipment.

The vast majority of our customers prefer to install their hot tubs outdoors, but our tubs can be installed just as easily inside your home as out.

Our Hot Tub Photo Gallery is full of unique location ideas, creative inspiration and great examples of where other hot tub owners have located their hot tubs.

Location of Your Hot Tub

Roberts Hot Tubs has been in business for over 42 years and history has taught us that your tub will be used and enjoyed more often the closer it is to your house or bedroom.

Installing your hot tub on or submerged in an existing outdoor deck is ideal for many hot tub owners, but please be aware that most decks are not designed to support the weight of a hot tub filled with water.

We strongly advise that all hot tub owners considering tub installations on existing decking check with a licensed engineer prior to beginning tub installation. Please remember that the average hot tub filled with water weighs approximately 5000 lbs. before you and your friends jump in!

Outdoor Installation Locations

Depending on where you live and the size of your yard, there can be an endless number of ways and places to install an outdoor tub.

That said, there are certain health and safety restrictions that will influence where your tub can be located.

  1. For stability and settling purposes, the tub itself must sit on a single solid concrete surface. Everything settles over time and just like the concrete slab under most homes, concrete settles but remains flat. Please do not set your tub or equipment on gravel.
  2. The tub rests on chine joists (sleepers) that we provide rather than making direct contact with the concrete pad. The size of the concrete pad can be 6 inches smaller than the tub’s diameter, so a 6′ diameter tub only requires a 66” round or square concrete pad.

Saving 6″ on the pad means pouring less concrete as well as insuring that the pad won’t protrude any farther out than it absolutely has to. The typical thickness of the concrete pad should be 4″ with mesh wire reinforcement.

  1. The type of ground underneath the pad should be stable as well with 100% compaction. If the soil has a propensity for expanding and contracting due to extreme temperatures, you may be required to add concrete footings to stabilize the pad. Checking with a local contractor is an easy way to find out whether you need footings or not.
  2. The overall height of the tub is also a consideration. A 4′ tall standard hot tub will stand a roughly 50″ off the top surface of the concrete pad with some exceptions of our other tubs.

Based on this height, you may want to consider sinking part of the tub into the ground. Sunken tubs are extremely popular and are much easier to get in and out of.

In order to safely “sink” your tub, you will need to dig/construct a tub vault. The vault should have retaining walls to keep any excess dirt from eroding and coming into contact with the tub itself throughout its lifespan.

We recommend that there be a minimum 12″ clearance between the walls of the pit and the tub itself; a 5′ diameter tub will need a 8′ diameter pit. Another thing to keep in mind is that the tub will require a minimum of 24″, preferably 36″, of clearance around the entire tub. This will allow the tub to be assembled above the pit and then lowered down.

Indoor Installation Locations

Indoor installations aren’t that much different than outdoor installations, but they do require a few extra considerations.

The main consideration with indoor installations is moisture and the effect it has on other areas of your home.

  1. Moisture – It’s common practice to use hot tub insulated covers on outdoor hot tubs and the same is true with indoor hot tubs. Insulating covers save time, money and energy inside and outside, but quite a bit of steam is released when you take off an indoor cover.

Steam doesn’t play well with other interior sections of your house, so you need to make sure that the room your tub is located in has good air flow and very good ventilation to include possibly a motorized fan similar to a bathroom.

  1. Chemicals – Along with the steam factor, there’s also the issue of sanitation and the use of hot tub chemicals. Hot tubs that are used regularly need to be sanitized with chlorine, bromine or a non-chlorine shock treatment in combination with smaller amounts of chlorine or bromine.

These sanitizers can produce foul smelling odors that go well beyond the room your hot tub is located in. Ozone is another form of sanitizer that should not be used indoors. High concentrations of ozone can accumulate in the room that your tub is located in and cause severe throat irritations as well as corrode plastic and printed electronic circuitry.  A motorized fan should be installed to evacuate the off gassing from the room.

The best sanitizer to use indoors is an ionizer in combination with periodic non-chlorine shock treatments. One maintenance advantage to indoor installations is that less dirt, debris and pollen get into your tub which might save you a few dollars per year on sanitizers.

  1. Leaks – The other big moisture consideration is “leaks.” As much as we hate to admit it, the possibility of an indoor hot tub cracking, breaking or leaking does exist, and the odds increase as the tub gets older.

After years and years of use, a seal or gasket could wear out and cause anything from a small drip to a giant flood. We strongly recommend that indoor hot tub owners take special precautions by installing a waterproof flooring membrane and floor drain in the room that the tub and equipment are located in.

If the tub equipment is installed in a garage or basement, it’s a very good idea to set the equipment in a waterproof pan with a drain to insure that any possible leaks won’t damage surrounding items.

Accepting Delivery of Your Hot Tub

Accepting Delivery of Your Hot Tub

Accepting Delivery of Your Hot Tub – BIG BOXES ON A BIG TRUCK

The majority of our hot tubs and complete hot tub systems are delivered by various Transportation companies (deliveries within the state of California are usually through DHL).

On the day we ship your tub to you we will call you to let you know that it’s shipping and to tell you the number of packages and the “pro number” (tracking number).

Once the shipping company has your shipment at its docking facility closest to you, they will call you to arrange delivery.   Keep in mind that the size of your shipment is rather large. Complete gas fired hot tub systems consist of three ‘packages’, the hot tub bands (approx. 60 lbs.), the heater (approx. 115 lbs.) and everything else in a VERY big box (roughly 6′ x 4’ x 3′ weighing about 500 lbs.).

Electrically heated systems consist of only 2 packages, the bands and the big box as shown in the picture to the right.
When arranging delivery with the shipping company there are a couple of things that may need to be considered for an easy delivery. First, let them know if there may be a problem in navigating a large truck to your home.

Trucks smaller than the standard ‘tractor trailer’ are available. The second, and more important consideration is how to get a 500 lb. box out of a trailer 5′ off the ground. Unless you happen to have a forklift sitting around, you may want to request a truck with a lift gate.

Please note we prepay delivery with the freight company to the street curbside with a  lift gate. Many people simple unpack the box right from the curbside (usually this only takes 5 to 10 minutes).

With a lift gate you can generally expect some assistance from the driver in getting your shipment from the truck to the curbside. If you need additional help to move the packages, when the freight company calls to schedule with you, bring up your needs with them at this time.

Our hot tubs are packaged with the utmost of care. Consultation with various shipping companies over the years has resulted in a method of packaging that can withstand thousands of miles of bouncing down the road, crashing into by forklifts, and even hours of sitting out in the rain.

Once your shipment is off the truck, however, inspect the package carefully for any exterior damage. If any damage is seen make note of it on your “bill of lading”, takes pictures and better yet open the package and inspect the contents. Also check the bill of lading as to how many packages are in your shipment and MAKE SURE this is the number you receive.