Siting and Drainage

Water is the enemy

The NPS names moisture as the chief cause of deterioration in log buildings: leaking roofs, failed gutters, splash, poor grading, and logs in contact with soil ¹. Rot fungi and insects need damp wood; keep the wood dry and most problems never start.

Choosing a site

• High and dry: a slight rise or a gentle slope, never the lowest spot, which collects water and cold air.
• Firm, undisturbed subsoil: avoid fresh fill, which settles, and organic soils.
• Read the ground: where does snowmelt run in spring? Where does water stand after rain? Cattails, sedges, and moss mark wet ground.
• Sun and wind: in Wisconsin, a south-facing site warms in winter; shelter from northwest winds; leave room for snow to slide off roofs.
• Setbacks: shoreland zoning and setbacks from water, lot lines, and wells apply, especially for a lakeside sauna; ask the county zoning office first.

Frost and soil

Frost heave happens when water in fine soils - silt and clay - freezes into growing ice lenses that lift whatever sits on them. Dry, coarse gravel heaves little. That’s why foundations go below frost (48 inches minimum for Wisconsin dwellings ²) or sit on well-drained gravel, and why drainage and frost protection are really one problem.

Moving water away

1. Grade: the ground should fall away from the walls on all sides - a common rule is 6 inches of drop in the first 10 feet.
2. Roof overhangs and gutters: wide eaves keep rain off log walls; gutters and downspouts carry roof water well away from the foundation ¹.
3. Splash height: keep sills and the lowest logs or siding 12-18 inches above grade; rain splashes surprisingly high.
4. Perimeter drain: at a full foundation, perforated pipe in washed gravel at the footing, wrapped in filter fabric, drains to daylight downslope.
5. Gravel: a gravel apron or a gravel pad under piers drains and discourages plants growing against the walls.
6. Ventilation: leave crawl spaces and the space under pier-supported buildings open so air dries the sills ¹; skirting should be vented.
7. Plants away: no shrubs, firewood, or soil piled against walls.

Checklist for a small building

• Site on a rise with firm subsoil; water falls away on all sides.
• Piers on firm footing stones, or footings below frost for a heated building.
• Sills of rot-resistant wood 12-18 inches up, with open, ventilated space beneath.
• Generous overhangs, gutters to daylight, gravel apron, nothing piled against the walls.
• Check zoning and code before building.

What to take from this

Moisture is the main enemy of timber buildings. Site on high, firm, well-drained ground; grade away from the walls; use wide overhangs and gutters; keep sills 12-18 inches above grade with ventilated space beneath; and drain the footing. Frost heave comes from water freezing in fine soils, so good drainage and below-frost footings solve the same problem.