The lake is the problem
On a road-access build, a forgotten delivery is a phone call away. On an island build, it is a week away. The construction-management discipline required to avoid that, every delivery scheduled, every contingency on the manifest, defines the project from day one.
Pre-construction takes longer. Trade procurement happens earlier. The contingency in the budget is meaningfully larger.
How materials actually get there
Winter ice road. The single largest delivery window. Structural steel, precast, concrete batching equipment, lumber packages, and heavy mechanical move across the ice. The window is real, engineered ice thickness, official municipal approval where required, and a hard close date when warming begins.
Open-water barge. Spring through fall. Slower, dependent on weather, more expensive. Used for finish materials and ongoing trade movement.
Helicopter. Reserved for emergency or specific oversize items.
Mechanical assumptions
Assume off-grid resilience. Even when grid power is available, a multi-day outage during a winter storm is a real possibility. Generator backup, propane on-site, and where possible solar with battery, become standard rather than optional.
Water: drilled well or lake-draw with full treatment, depending on the lake.
Septic: standard tertiary system, sized for full-house use.
Communications: fibre run from the mainland where possible; otherwise satellite.
Construction management discipline
Weekly delivery manifest. Every item, every supplier, every barge slot.
On-site staging. The cottage site has to hold months of material at a time.
Trade contracts that explicitly address travel time and accommodation.
Owner-side construction management is the right model for an island build. The accountability structure has to be tight.