The Schundler Company
10 Central Street
Nahant, MA 01908


When vermiculite aggregates (Schundler V+16 Pool Base) or premixes of vermiculite and portland cement (Ultra Mix or Ultra Mix II ) are not available, perlite concrete can be used instead.

The Schundler Company has been processing perlite and vermiculite for decades, and was the first company to promote the use of vermiculite in the construction of vinyl liner inground pools. We recommend these lightweight concrete bottoms because:

Vermiculite vs. Perlite:

We have always recommended vermiculite because it is a much softer, pliable mineral. As a result, vinyl liners will tend to wear down a little faster with perlite (BUTboth perlite and vermiculite will wear down liners much less than regular grout mixes.)

We recognize, however, that in some parts of the country, it is very difficult to find distributors and dealers of vermiculite. As a result, we have provided this page for those who need to use perlite.

Essentially perlite should be mixed and trowelled just like vermiculite. With perlite, however, a little air entraining agent will help make the perlite mix better. (Use regular non-sudsing soap if you don't have any air entraining agents available.)

From the Perlite Institute, the following Product Guide might also be helpful:


Perlite insulating concrete pool base can substantially reduce heat loss to the ground thus keeping pool water warmer for a longer swimming season and reduced energy costs when pool water is heated. In addition, perlite pool base provides a firm, smooth, foundation that prolongs the life of vinyl liners.


Perlite insulating concrete is placed following the erection of the pool walls. The concrete is site mixed using paddle-type mixers, poured into the base area and screeded to the proper contour. It is recommended that the surface ahead of the pour be kept very moist and that the perlite concrete be fog sprayed every 15 minutes until the liner is installed. It is further recommended that the foundation not be less than 1-1/2 inches (4 cm) thick. Above the coping sides, a 1 inch (2.5 cm) thickness is sufficient. The vinyl liner is installed and the pool filled immediately following concrete placement to eliminate dimpling problems and to smooth imperfections in the pool bottom. It is recommended that the pool not be used for 48-72 hours.

Typical Mix Proportions per Cubic Yard (Cubic Meter) for Perlite Insulating Concrete Pool Base
7 lb/ft3 (112 kg/m3 ---Perlite Aggregate Based on 100% Yield
CementPerliteAir Entraining Agent**WaterFibers***
*One bag (sack) of cement weighs 94 pounds
**14% Neutralized Vinsol Resin. Omit AEA if plastic cement is used
***Fibers 3/8 in (1 cm) nominallength, alkaline resistant, 15 denior, polypropylene

Mix Procedure

It is essential that the proper mixing procedure be followed to achieve best yield, workability, and uniformity.

  1. Water, AEA, and portland cement should be added to the mixer in that order. These components should be mixed one or two minutes until the slurry is uniform.
  2. Perlite aggregate should be addd to the slurry, additinal water added if necessary, and mixing should continue only long enough to create a uniform mix (one or two minutes.) A proper mix will have a creamy consistency that will hold its shape without being runny. The inclusion of fibers will help eliminate dehydration cracking.

Over mixing can cause loss of yield, poor workability, and rduced strength. After the mix is uniform, and if there will be a delay in pouring the perlite insulating concrete, the mixer blades should be disengaged.

We hope this brief description of Schundler Pool Base is helpful. For more information, please call or contact your local dealer or:

The Schundler Company
10 Central Street, Nahant, MA 01908
732-287-2244 or

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