Observatory Construction: Foundation
My friend Jim Elmer of Elmer Construction constructed the foundation of the building. The building outline was 20' x 32', divided into two rooms. The slab for the 20' x 20' observatory room was structured to be 8 inches higher than that for the 12' x 20' warm room so that the walls of the observatory room could be at the nominal 7' height recommended by Backyard Observatories, while making the ceiling of the warm room a more comfortable 7' 8" in height. The north side of the foundation was extended to create an 18' x 20' patio, which also served as a sturdy foundation for attaching the posts for the roof rail system.
Jim prepared the forms and several loads of gravel were brought in and compacted to establish the height differential and prepare for the concrete.
In anticipation of mounting a permanent instrument, I had Jim install a 2' x 2' concrete pier that was isolated from the main slab. Jim attached rebar to the bedrock below and formed a 2' x 2' box to hold the concrete. The pier was designed to be level to the surface of the slab, and can be later augmented with concrete or a pre-fabricated metal pier, as desired.
Two conduits were installed under the slab from the pier to the warm room, more than enough for any anticipated wiring needs.
Three concrete trucks were needed. The left over concrete was used to construct a 14' x 14' pad near the building, which can be used by visitors or serve as a base for a storage shed or even a small dome.
Observatory Construction Pages