Hot tub cover specifications

by Sally Bouorm | June 1, 2011 2:58 pm

Hot Tub In The Woods - A large deck in the woods with a hot tub outside the lanai.[1]
The dealer should never assume his/her customer realizes every detail that is needed to fabricate a new cover.

By Aleta Mann

Replacement hot tub covers are custom made and not stocked by manufacturers the way they are in retail stores, which is why it is extremely important that specifications are accurate when orders are placed. Cover manufacturers rely on getting all the details when a product template is not available. Otherwise, the customer could face the costly prospect of paying for a remake.

Providing detailed replacement cover specifications can be a daunting task; however, this article will help simplify the process and ensure a good seal and an attractive fit.

It’s all in the details

The dealer should never assume his/her customer realizes every detail that is needed to fabricate a new cover. Most manufacturers will provide the dealer with an order form showing various options and shapes, in addition to which measurements are required. This form should be read carefully, as it will help to ensure no detail is missed.

It is also important to check with the manufacturer for available cover templates by providing, if possible, the make, model and year of the hot tub. More than one model with the same name may exist and a conscientious manufacturer will verify that the template matches the dealer’s needs. If a template is not available, measurements must be provided.

Made to measure

The first step is to measure the hot tub’s length and width. Measure across the centre both ways, from the outer acrylic lip to the outer lip on the opposite side. Always provide the size of the actual cover being ordered rather than the water-to-water measurement. Otherwise, the cover will fall into the hot tub.

If the cover is a rectangle or other shape in which the length differs from the width, draw the fold on the order form or submit a drawing. If the cover is circular, only the diameter measurement is required. Normally the fold is parallel to the short side, dividing the long side in half.

Always provide the size of the actual cover being ordered rather than the water-to-water measurement.

Measurements can also be taken from an existing spa cover. Keep in mind, however, this measurement will already be a little larger than the hot tub measurement. Therefore, it is extremely important to notify the cover manufacturer if the measurements were taken from the hot tub or the cover, as well as if any extra length or width has been added.

Measurements for inground hot tubs should include extra width and length—a minimum of 76.2 mm (3 in.) on all sides—so the coping will support the cover. Be sure to let the cover manufacturer know the measurements are for an inground hot tub and whether the cover will rest flush with the coping or if the hot tub is raised. It should also be specified whether the cover requires a skirt or straps—covers for inground hot tubs are often made without either.

Cover thickness measurements can also be taken from the existing cover. The thickest edge of the insert is usually the edge next to the fold. Measure the thickness from top to bottom, in addition to the thickness at the outer edge. Most hot tub cover foam is tapered; common tapers include, 101.6 to 50.8 mm (4 to 2 in.), 101.6 to 76.2 mm (4 to 3 in.) or 127 to 101.6 mm (5 to 4 in.).

Weather factors and energy savings should also be considered. The thicker the cover is the better—especially in colder climates. This also applies when selecting foam density, which indicates how tightly the foam beads are packed together within 0.09 m2 (1 sf) of foam. In other words, 0.68 kg (1.5 lbs) density means 0.09 m2 (1 sf) of foam would weigh 0.68 kg.

Cutting corners

Next, consider the corners of the hot tub cover—are they square, radius (rounded), cut or another shape? These measurements must also be provided to the cover manufacturer, and depending on the cover’s corner style, the following will help simplify this task.

Radius corners

Measurements are not required for square corners; however, when dealing with radius corners, a carpenter’s square is required. Place the square on the outer corner of the hot tub’s acrylic lip and note the point where it begins to curve away. Measure the distance from this point to the inner corner of the square. Check the same distance on the opposite side, as these measurements should match. This distance is the radius measurement. If a carpenter’s square is not available, two straight edges can also be used.

To measure a radius corner place a carpenter’s square on the corner of the hot tub or on the corner of the existing cover. If in doubt, trace the radius corner and send with the order.

Another way to measure radius corners is to trace them. Secure a sturdy piece of clear plastic or a sheet of paper over the entire corner with masking tape. Carefully trace the outer edge of the corner with a magic marker from beginning to end. This drawing can be faxed or mailed to the manufacturer.

If the radius corner measurements are incorrect, the cover may not seal properly and it may lose its visual appeal. (If the radius is within 25 mm (1 in.) or so, the cover will usually look fine). The larger the radius, the broader the curve. If a cover with a 304.8-mm (12-in.) radius corner is placed on a hot tub with a 152.4-mm (6-in.) radius corner the corner of the spa will stick out from under the cover, leaving a gap. The cover’s skirt will also be uselessly crushed underneath.

If the opposite occurs, with the spa having a larger radius than the cover, the corners of the cover will extend out over the lip of the hot tub, creating an improper seal and added opportunity for wind to catch it.

Cut corners

Cut corners also need to be measured. The length of the cut corner itself should be provided along with the measurements of the other sides of the cover. As always, remember to take care in providing the full length and width of the hot tub.

Although it may seem elementary, be sure to measure hot tubs with one cut corner from the topside to ensure the cut corner ends up in the right place. And, always draw the fold for hot tubs with one- and two-cut corners when ordering.

A common pitfall with four-cut-corner hot tubs is the distance between the cut corners is often provided instead of the full measurements. This results in a cover that is too small.

When dealing with an equal-sided octagon, all sides should be measured to make sure they are in fact equal—then only the diameter and side measurements need to be submitted.

Sometimes cut-corner hot tubs have radius corners, as well. These should be measured in the same manner as any larger radius corner. If in doubt, trace the radius. Since cut-corner hot tubs seem to be the most challenging to measure, a template can also be submitted.

No skirting around

The skirt is a flap of material that usually extends from the bottom of the cover to the bottom of the hot tub’s acrylic lip.

Measure the skirt from the bottom of the cover to the hem, or from the top to the bottom of the acrylic hot tub lip.

In some cases, a standard skirt length (approximately 63.5 mm [2.5 in.]) is included unless a specific measurement is included on the order form or indicated in the template database. If the hot tub cabinet has a protruding top rail, the cover may need to be ordered larger to allow the skirt to hang free. Another alternative is only measuring to the top of the rail so the skirt and rail just meet.

It should also be noted whether there are slits in the corners of the skirt or any area where the skirt length may differ. For example, spill-over hot tubs may have a flap on the skirt to cover the spill-over opening.

Measure the cover strap from the bottom of the cover to the bottom of the hardware.

Cover strap measurements and locations are also important. Standard strap lengths are usually 203- to 228-mm (8- to 9-in.) long. If a different length is required and strap measurements are provided, be sure to indicate whether the measurement includes the length of the strap hardware. Also, if the straps need to be in a specific location, mark the drawing or template with an ‘X’ to indicate their position.

Finally, are there any cut-outs in the top of the cover? If so, a rough drawing should be provided detailing the cut-out’s length, width, depth and shape, along with its position on the cover. It should also indicate whether the foam, vinyl or both are being cut out.

It’s all in the details

It is always helpful to receive a rough drawing of the cover specs. When a hot tub is unusual in any way, not only a drawing, but also a cover template or pattern may be required. Digital photos are also extremely useful when fabricating custom hot tub covers. With the increasing demand for natural shapes and landscaped hot tubs, details are important, as they allow the cover manufacturer to determine what designs are possible, as well as make recommendations on the best way to fabricate the cover.

Creating a template

To create a template, place a sturdy, clear-plastic drop cloth on top of the hot tub and secure it with masking tape. Then, trace the hot tub’s outer lip with a heavy marker, making sure to draw one continuous line without breaks. Finally, write ‘top’ on the upper side of the template. Another option is to lay the existing cover on top of the drop cloth to create the outline.

It is okay to show the water-to-water line within the template; however, a clear outline of the actual cover size is required. Fold lines, strap positions and cut-outs should also be indicated on the template.

Never use the vinyl jacket of an existing cover as a template, over time it can shrink, stretch or dry out and result in a poor fit. However, a new vinyl jacket can be fabricated by submitting the measurements, taper and density of the existing inserts. Replacement inserts can also be fabricated from these measurements.

When submitting insert measurements for an entire cover, it is okay to provide the manufacturer with the dimensions of only one insert, as long as both halves are exactly the same size. The order form should also indicate a half measurement was provided, otherwise the dealer may receive a 1.2- x 2.4-m (4- x 8-ft) cover, when the hot tub is 0.7 m2 (8 sf).

Be sure to include the cover’s colour, taper and desired foam density, along with any other special features on the order form. Once the manufacturer receives the template, they can generate a final quote.

When in doubt, call

These are the basic steps required for measuring a custom fabricated hot tub cover. If any facet of the job becomes troublesome, call the cover manufacturer for assistance, as they can help solve any problems to ensure the job is done right the first time.


Aleta_Mann_HeadshotAleta Mann is the vice-president of sales and marketing for Commercial Fabrics Inc., a spa cover manufacturer in Niagara Falls, Ont. Her experience as a marketing professional spans more than 30 years in many facets of advertising and sales. She can be reached via e-mail at[6].

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