The Neptune Pool at Hearst Castle is perhaps the most exciting and beautiful renovation project a tile and stone contractor could ever imagine. Located on a bluff overlooking the Pacific Ocean above San Simeon, CA, this iconic marble pool was inspired by the stunning location and equals the extravagant architecture of the castle itself. When cracks and leaks in the 90-year-old landmark required repairs and a complete replacement of the tile, a full system from Custom Building Products was selected to install the new stonework. 

Originally designed by publishing magnate William Randolph Hearst’s architect Julia Morgan in the 1920’s, the Roman-themed Neptune Pool was expanded three times until it reached its current size in 1936. It now holds 345,000 gallons of water, measures 104 feet long by 58 feet to 95 feet across and reaches a depth of 10 feet. The pool is an engineering marvel, being suspended rather than sunken; this factor added an extra layer of complexity to shell and plumbing repair efforts at the site.

Commissioning a renovation

By 2014, the aging pool was leaking up to 5,000 gallons of water daily during a devastating drought. After draining the pool to prevent further leaks and assess damage, all original tile had to be removed to allow extensive repairs to the shell. A complete renovation was commissioned by California State Parks, which owns and maintains this extensive property. Following repairs to fill cracks and other imperfections, application of a crystalline waterproofing solution and a successful 14-day fill test, the tile installation began in earnest. 

The natural stone tile work on this project was awarded to the third-generation marble craftsmen at Carnevale & Lohr, Inc. of Bell Gardens, CA. Their union stone masons and tile setters are trained in time-tested and traditional hand-fitting methods, but also incorporate modern tile installation technology, standards and techniques. This way, the installers brought together the best of the old and new worlds of tile craftsmanship. 

“Custom’s products are excellent, but this project also needed to be about the technical support, best warranty and partnership of the installation products manufacturer,” said David Carnevale, president of Carnevale & Lohr. “Custom offered their testing labs and all of their resources to us. That was something different, and it counted for so much.”

Preparing the surface

Surface preparation was carried out by experienced union installers from subcontractor Charles McCandless Tile Contractor, Inc. of Santa Ana, CA. To smooth the surface of the pool shell, workers spread Quikrete® Deck Mud fortified with Custom Thin-Set and Mortar Admix at a depth of ¼ inch up to 1 inch in places. This pre-blended leveling mortar is formulated for low shrinkage and saved the labor of powder blending at the site, while the addition of polymers improved performance and flexural strength. After curing, a bond coat of thin-set mortar was used to prepare the shell for receiving a membrane. 

RedGard® Waterproofing and Crack Prevention Membrane was specified to help isolate cracks in the substrate and waterproof the surface preparation and mortar bed. A liquid-applied elastomeric membrane was indicated due to the size of the project and the rounded surfaces throughout. The membrane was roller-applied for the best control of wet mil thickness to exceed the requirements of ANSI A118.10 and A118.12. Three full-strength coats of RedGard followed an initial primer coat for a total of 45 dry mils. After curing, each successive coat was applied at a right angle to the previous one to provide the highest level of protection.

“With RedGard, the ease of application and not having any seams is a huge plus,” said Mark McCandless, president of McCandless Tile. “On top of that, the team at Custom provided a great system, technical assistance, coordination with the design team and a warranty.”

Hearst Castle is a designated National Historic Landmark to protect the architectural masterpieces located at this unique site in California history. This status required an exact color and material match to reproduce the classic patterns of the original marble tile installation. Prior to demolition, 3D laser scans were used to map the tile in the pool to within ¹/₈ inch. From this, dimensioned shop drawings were produced to plot the location of individual tiles and their relation to other pool elements. Honoring its first builders, the original Vermont quarry locations were located by a team from the state and used to source the new marble and serpentine needed to bring the pool back in all of its glory.

Installing the marble tile

All of this planning was followed by the painstaking installation of over 19,000 stone tiles involving countless referrals to photos, plans and other documentation of the original pool. Tiles were carefully fabricated and sorted by character to best replicate every detail of the historic project. Skilled masons set 3,000 square feet of Vermont Verde Antique® serpentine and 7,000 square feet of Olympian White Danby® marble. To match the original pool, the new stone was also cut to ¾ inch thick, so it was quite heavy at 12 pounds/square feet. MegaLite® Ultimate Crack Prevention Large Format Tile Mortar was specified for setting the natural stone in this challenging environment. This mortar exceeds ANSI A118.15 TE for use up to ¾ inch thick to support heavy tile and prevent lippage. 

MegaLite offers the highest bond strength for the most demanding installation requirements and has the flexibility to withstand horizontal substrate movement. The lightweight formula provided excellent handling characteristics, including less fatigue for installers working with heavy materials. Thixotropic properties provided the non-sag, non-slump performance needed for setting natural stone on both the bottom and vertical sides of the pool. 

The adhesive mortar was keyed into the substrate. Then, additional mortar was combed in straight lines using the SuperiorBilt® Premium Notch trowel; this tool is designed to promote ridge collapse once the tile is set. Following industry best practices, trowel ridges were placed running parallel to the shortest side of rectangular tiles to facilitate air release. Each stone tile was back-buttered prior to being placed. Finally, tiles were moved across the trowel ridges to collapse them, release air and prevent voids behind the tile. 

The stone workers used soft rubber mallets to beat in the bedded tile for a flat tiled surface.  Suction cups were used to periodically check mortar coverage and transfer to ensure that it met the 95% requirement for natural stone, exteriors or wet areas.  With the pool combining all of these elements, proper ridge collapse and coverage were especially important to protect the tile per ANSI A108.5.2.5. 

The Neptune Pool’s marble and serpentine tiles were grouted with PolyBlend® Non-Sanded Grout. After testing with samples of the stone and historic small joints between tiles, the sand-free formula proved ideal for the project. This durable, non-shrinking, polymer-modified grout can be used to fill joints up to ¹/₈ inch. Bright White was the shade used to replicate the original grout, which long pre-dated colored grouts.

“As Californians, we take tremendous pride in this project,” said Jim Christenson, fieldsuperintendant at Carnevale & Lohr. “Everyone was very excited to watch the pool comeback to life.”

Neptune Pool, Hearst Castle

San Simeon, CA

Project Owner: California Department of Parks and Recreation, Sacramento, CA
Original Architect: Julia Morgan
Architect: Page & Turnbull, San Francisco, CA
General Contractor: T.B. Penick & Sons, Inc., San Diego, CA
Conservator: Risser Conservation Services
Stone Suppliers: Vermont Quarries Corporation, Mendon, VT (Olympian White Danby marble); Vermont Verde Antique LLC, Rochester, VT (Verde Antique marble)
Stone Supplier & Consultant: Sutherland Falls Stoneworks Inc., Proctor, VT
Installation Consultant: Ceramic Tile and Stone Consultants of Jamul, CA
Stone Fabricator & Carver: Proctor Marble Company, Proctor, VT
Tile Contractors: Carnevale & Lohr, Inc., Bell Gardens, CA; Charles McCandless Tile, Inc., Santa Ana, CA
Installation Products: Custom Building Products, Huntington Beach, CA