Using component systems to build caves and grottos

The construction process

Since these components have a steel structure, a bond wire is required to meet most building codes. The concrete pad should have a bond break at the pool shell and should slope toward the pool. It is also recommended there be at least 102 mm (4 in.) of concrete on the pad. In addition, the construction of caves and grottos require concrete backfill.

Placement

Base components should overhang the pool beam by 25.4 to 51 mm (1 to 2 in.) to minimize any chance of seepage under the waterfall. The base components and ledgers generally have a dripline, but water might still run down the face of a rock. The most popular size cave/grotto is 3 m (10 ft) long and 1 m (3.5 ft) tall, with an approximate 1.2 m (4 ft) wide ‘cave area’ for sitting that is 0.5 m (1.7 ft) above the pool’s waterline.

Handholds

If the cave/grotto is placed in an area of the pool with more than 1.2 m (4 ft) of water, building codes typically require a ‘handhold’ to be installed. This can be done by setting the waterfall back from the beam about 51 to 76.2 mm (2 to 3 in.), but the beam must slope toward the pool to prevent seepage. In these cases, 228.6-mm (9-in.) coping is often used to create a handhold to extend the rock into the pool.

Mortar techniques

Today’s component system castings can be quite dense and they do not absorb water so they must be set with a rich mortar mix. Most masonry supply businesses and home improvement stores have a ‘better quality’ mortar mix or cement that can be blended with masonry sand, which work well. Mortar should be easy to trowel into place—not too runny or stiff. Mortar beds should be 25.4 mm (1 in.) or more for base pieces and less for smaller rocks. For maximum bonding, mortar should also be scrubbed to the underside of the rock.

On a radius or corner, gaps need to be filled. The small rocks that come with each kit can be used or coping can be cut to fit and fill any gaps.

The mortar should be left to set; do not smear fresh mortar. After it has hardened, it can be cut and brushed away. A slight undercut will provide a nicer finish. Some installers use antiquing to age the joint after the mortar is dry, while others like to use rainbow cement for mortar so it will dry the same colour as the castings.

“We found it extremely easy to blend the seams,” says Duhon. “It gave us peace of mind to not have to worry about rain messing up colour matching as the rocks are pre-coloured. Having to only colour and blend the seams saves an incredible amount of time.”