Built-in plaster and Gunite spas require a different approach than standard portable hot tubs.
Because they are built into the deck or patio, the cover must be measured and designed around the way the spa is installed.
For an in-ground spa cover, proper fit is not only about appearance. The cover needs enough support on the surrounding coping, the correct overall dimensions, and a layout that works with the actual shape of the spa.
Why Custom Fit Matters for an In-Ground Spa Cover
Many built-in spas are custom-built on site rather than manufactured to a standard size.
They may be:
- Round
- Oval
- Rectangular
- Octagonal
- Free-form
- Slightly out of square
That means a standard-size cover may not provide the correct support or coverage.
A custom in-ground spa cover is built around the actual dimensions and shape of the spa.
Measuring the Water Span Is Only the First Step
For a built-in plaster or Gunite spa, we normally start by measuring the water span.
This means measuring from the inside edge of the coping to the inside edge on the opposite side.
The cover then needs additional size so it can rest securely on the surrounding coping.
In many installations, approximately 6 to 8 inches total is added to the water span, giving the cover about 3 to 4 inches of support on each side.
The exact amount depends on the shape of the spa and the surrounding coping.
The goal is not to cover the entire coping. The goal is to give the cover enough solid support around the spa.
Proper Support Helps Prevent Premature Sagging
A cover that does not have enough support around the perimeter may place unnecessary stress on the foam panels and hinges.
For built-in spas, where the cover rests directly on the coping, proper support is especially important.
The cover should sit on a stable surface around the spa rather than hanging over too much unsupported space.
For larger or unusual shapes, the panel layout may also need to be adjusted so the sections are properly supported and practical to handle.
Heavy Duty Foam Is Usually Recommended
Built-in plaster and Gunite spas are often located directly at deck level.
Because of this, they are more likely to be accidentally stepped on than a raised portable spa.
For that reason, we almost always recommend Heavy Duty 2.0 lb foam for built-in in-ground spas.
For covers up to 96 inches, Super Foam 2.0 lb construction with a 5-inch to 3-inch taper is also available when additional insulation is desired.
No spa cover should be treated as a walking surface unless it is specifically designed and rated for that purpose.
Custom Shapes May Require a Template
Many in-ground spas can be built from accurate measurements.
More complicated free-form designs may require a full-size template.
A template may be necessary when the spa has:
- Irregular curves
- Multiple radiuses
- Angled sections
- Asymmetrical shapes
- Unusual coping layouts
The more complicated the shape, the more important it is to capture the actual outline accurately.
Hinge Direction and Panel Layout Matter
The cover should also be designed around how it will be opened and removed.
For a large in-ground spa, the hinge direction and number of sections can affect day-to-day use.
When planning the layout, we consider:
- Overall size
- Shape of the spa
- Available deck space
- Nearby walls or railings
- Landscaping
- How the sections will be handled
A well-planned cover should fit the spa correctly and also be practical to use.
Safety Depends on the Complete Cover Design
An uncovered in-ground spa can present a greater risk because it sits at deck level.
Qualifying spa covers up to 96 inches can meet ASTM F1346-91 requirements when properly constructed and equipped with four locking tie-downs.
Oversized covers over 96 inches are not ASTM child-safety rated, although locking tie-downs are still available.
Foam density alone does not make a cover child-safe.
The complete cover design, including dimensions, construction, reinforcement, locking tie-downs, and proper use, all matter.
Fiberglass In-Ground Spas May Need a Different Approach
Not every in-ground spa is plaster or Gunite.
A fiberglass spa may be installed slightly above the deck, flush with the deck, or recessed below it.
Depending on the installation, the cover may:
- Fit the spa shell closely and use a skirt
- Fit without a skirt
- Be made larger to rest on the surrounding deck
This is often a judgment call based on how the spa is installed and where the cover will have proper support.
Local Measuring and Templating
For local customers in Orange County and many areas of Los Angeles County, measuring and templating services may be available during the summer months.
For customers outside the local service area, we can help explain what measurements are needed and whether a template is necessary.
For complicated built-in spas, photos of the spa and surrounding deck can also help determine the best measuring approach.
How Long Does an In-Ground Spa Cover Last?
Based on our experience in Southern California, a typical spa cover often lasts about 4 to 6 years.
With favorable conditions, some covers may last another 1 to 2 years. Covers that are cleaned, protected, and maintained according to our recommended maintenance plan may last even longer.
Actual lifespan depends on:
- Sun exposure
- Climate
- Water chemistry
- Chemical vapor exposure
- Maintenance
- How the cover is handled
Regular cleaning, proper water chemistry, and the use of a recommended UV protectant can help extend the life of the cover.
Why Proper Fit Makes a Difference
A properly fitted in-ground spa cover can provide:
- Correct support on the coping
- Better coverage around the spa
- Reduced unnecessary heat loss
- A panel layout suited to the actual installation
- Better protection when the spa is not in use
Learn more about available options on our In-Ground Spa Covers page.
Need Help With an In-Ground Spa Cover?
Spa Covers Etc. has been helping customers with custom spa covers since 1997.
For help with measurements, templates, unusual shapes, or a custom quote, call Chris at (949) 496-2883.
We’ve got your spa covered!
