Dome in the Maryland Woods

Dome Construction

Dome house at 6805 Simms Mill Place, Bryans Road, MD 20616.

This building was designed with the following principles in mind throughout. The building would be built to last. The quality and sizing of structural members, the depth of the foundation, and the robustness of the wiring were chosen to that end. The design assures good drainage around and under the house. A premium was put on creating a great flood of natural light and a feeling of spaciousness, with and an open design.

The first floor of the dome is somewhat in excess of 700 square feet. The upstairs loft adds about 350 sf more.

The front door was originally framed for a custom-made 38” wide door. Since then I changed to a more conventional door, and I framed it in; but it would be easy to reframe and install a wide door again. There is a back door and a side patio door. Each is accessed by covered landings with plain wooden steps.

Once the site was cleared for the original construction, I hired a backhoe operator to dig a 30-foot diameter circle 48” deep – 18” deeper than code, well below the frost line, to promote long term stability. Into that circle I had concrete poured 24” wide and six inches deep. On top of that a fifteen-sided polygonal block wall 30’ in diameter was built over six feet high (from the bottom of the trench up). The blocks had to be cut and cemented together to form an angle of 156 degrees at each of the 15 vertices. Then the wall was parged. In the first six months of construction, I had a French drain installed around the foundation, and ever since then the tall crawl space has always stayed dry even in very wet weather. The water heaters and the well water storage tank are situated in the crawl space.

Inside the crawl space two piers were built on footings matching the 48” depth of the footings for the exterior parged walls. These piers support the central span of the floor beam. The floor beam is three 2x12’s thick for the entire 30’ length except for the central span, where the beam is reinforced to be five 2x12’s thick. The sills and floor joists are 2x12’s.

The central span of the floor beam is five 2x12’s thick. An architect who consulted on the plans agreed that this was more than sufficient, and in fact, robust. The architect’s approval of the plan was required by Charles County in 1983.

The first floor walls are 10 ½ feet high, framed with 2x6’s, insulated, and with double headers. There are fifteen walls making a regular polygonal footprint, each wall 6’ 4” long, for a total of about 100 linear feet of 2x6 wall with fifteen vertices. The exterior is clad with T1-11 siding. The interior paneling is made of Lauan plywood. The 20’ high dome rests on the approximate circle formed by the headers atop the first floor walls, and a second floor loft was built, a pie shape about 3/5 of the approximate circle of the ground floor footprint. The distance from the top of the interior of the dome down to the floor on the 2/5 part of the ground floor with no upstairs is 30’.

The 10’ 6” walls are a unique feature of this dome. The ground floor itself is already high-ceilinged, reinforcing the feeling of space and airiness.

The electrical service is 200 amps. All the 120 volt circuits are wired with 12-3 copper Romex (one black, one white, with ground), and all electrical boxes are of galvanized steel and the Romex is grounded to them. There are 220 volt circuits for the well, the HVAC, a dryer, and a couple more still unused 220 circuits. There are numerous Ground Fault Interrupter circuits. There is at least one receptacle, one light switch and one lamp base controlled by the switch on each of the 15 walls. There are windows in almost every wall, and all windows are double glazed.

The dome is five eighths of an icosahedron, approximately 5/8 of a sphere. built of 2x4 construction for the struts, and ¾ inch plywood for the hubs. The struts are joined to the hubs by glued double doweling on each end of each strut. The roofing is done with fiberglass shingles and a great quantity of very generously applied clear silicone caulking that was rated for 50 years. The shingles were effectively glued down with this calking. Two reversible direction variable speed ceiling fans are installed near the top of the interior of the dome.

The dome has a dormer, eight feet wide, 9 ½ feet high. The peak at the top extends four feet from the dome. The dome has a door to a small ledge one can look out from.

About one-third of the dome has either skylights or translucent fiberglass panels. The two-pane fiberglass panels make up about one-quarter of the roof. Two of the skylights are made of double-paned acrylic ¼ inch thick. There are also five large operable skylights at the peak of the roof, These five skylights are made from triple-paned vacuum-formed acrylic. Where the dome roof is opaque and wood-covered instead of light-admitting, there is insulation with vapor barrier between the roof plywood and the interior paneling.

The dome has a front door, a back door, and a side patio door. A landing has been built at each door and there are plain wooden steps leading to each landing. Each set of steps rests on a concrete pad.

There is one bathroom, with a ceramic sink made by an artist, and a very long clawfoot bathtub.

The kitchen has ample cabinet space, using free-standing cabinets topped with a very large slab of polished marble, and built-in cabinets along the walls. The open design gives the feeling of spaciousness, with life flowing through the kitchen/dining/living area when entertaining.

The first thing one notices on entering the dome in the daytime is the great amount of natural light. In the summer this is moderated by the surrounding forest in which the dome is sited. The second thing one tends to notice is the headroom – a ceiling 30’ above the floor one is standing on.

The house is located on a 3.5 acre parcel, and contiguous with it is a 20.82 parcel, which goes together with the improved parcel in this sale. A second house site can be added. This would require a boundary line adjustment. A second perc site was approved, but not recorded. The approval has expired, but current practice of the Charles County Health Department makes reapproval much easier, with repercing probably unnecessary.

It is possible that on the far end of the property a third site might be approved. I have not explored this potential to any depth.

The overall design was done by me, the owner. The drawings were done by John Bentley of Guelph Ontario, then an engineering student, now a home remodeler. Mr. Bentley also made decisions on construction details. Details of the roof design were done by William Sleeth, at the time a student of landscape architecture, who later became a leading designer of public parks in Ontario.