Durability

Our soil is clay-rich and we have harsh winters. Clay-rich soil expands when wet and shrinks when dry. Similarly, moist soil expands when it freezes and shrinks when thawed. These forces pressure pool walls. A gunite shell is completely rigid. If the shell is not uniformly strong, or subject to uneven forces, the shell cracks to relieve the pressure. Repairing plaster cracks and re-attaching tiles in the Spring is expensive and prevents you from using your pool as you await repairs.  Gunite’s susceptibility to cracking is why they’re typically built either in places without winters (FL, TX, AZ) or in places with very well-drained sandy soil (Jersey Shore, Hamptons).

Most people want salt water pools for their lower operating cost, more precise chlorine control, and soft water feel. Fiberglass pool manufacturers don’t approve their pools for salt water applications because the salt causes the interior finish (gel coat) to take on a chalky hue in about five years.

Vinyl liner pools have some flex- not something you notice with your naked eye, but enough to safely relieve variable soil stresses. Vinyl liner pools never crack. They don’t have the regular repair issues of gunite pools. Vinyl liner pools are fully compatible with salt water, unlike fiberglass pools whose gelcoat finishes chalk-up after five years exposure to salt water.

Flexibility

Gunite pools are fully customizable. If it’s important to have a guitar-shaped pool or an infinity edge, gunite is for you. Otherwise vinyl liner pools have the design flexibility to meet your needs. 

Fiberglass pools’ size and shape are limited by what fits on a trailer over public roads- which is why 15’ x 39’ are their max waterline dimensions. Their design is also limited by the factory’s limited set of production molds- if you want a pool with a unique deep end, custom stairs, or stairs on a long wall, it’s not possible with fiberglass, but is with vinyl liner construction. Fiberglass pools are placed complete to the excavation with a crane. If you have trees between the road and excavation, you may have to cut them, lift the pool over your house, or use your neighbors yard to set the pool in place. Lastly, fiberglass pools are rarely more than 6’ in depth. If you want to be able to dive head-first in your pool, even without a diving board, fiberglass likely isn’t a good choice.

Vinyl liner pools can be made in any dimension with any bottom design and stair configuration. Vinyl liner pools are assembled on-site from smaller precision-made parts, so trees, structures, and other obstacles can remain in-place.

Value

Gunite pools cost about twice as much as vinyl-liner pools. Their maintenance is also expensive. They need to be replastered every 7-10 years, in addition to regular crack and tile repairs. Replastering is a labor-intensive job costing more than a liner replacement. A gunnite pool’s rough plaster finish is conducive to algae growth. It is much harder to keep a gunnite pool algae-free requiring more chemical treatments and labor.

Fiberglass pools are also more expensive than vinyl liner pools. The factory overhead, molds, transportation, and crane costs offset their labor savings. Heating costs are higher as they lack the insulating vermiculite bottom of Mountain Pools’ vinyl liner pools.

If comparing the cost of a fiberglass pool to a vinyl liner pool be sure to compare pools of the same size. A 14’ x 28’ vinyl liner pool has a waterline of 14’ x 28’ giving 392’ of wet surface area. Fiberglass manufacturers refer to the outer dimensions of their pools factoring the outer dimension of the shell’s top lip, not the waterline dimension you care about. A fiberglass pool described as 14’ x 30’ has a waterline dimension of 12.87’ x 28.83’ giving 371’ of water surface area. A 14’ x 28’ liner pool is actually 6% larger than a fiberglass pool described as 14’ x 30’!

Vinyl liner pools are the most efficient in-ground pool to build and operate. Construction cost is the lowest of the three in-ground pool types. Heat losses are lowest of the three pool types due to the insulated vermiculite concrete floors we install. Chemical demands are lower than for gunnite and equal to fiberglass.