By the early 1800s, many Americans had their eyes firmly fixed on the region around the Upper Mississippi and St. Croix River Valleys that later became part of Minnesota. Everyone who had traveled this wilderness area could see that it was a loggers’ bonanza just waiting to happen.
Two of the opportunistic lumbermen who took note of the region were the brothers John and Martin Mower. They moved from Maine in the early 1840s and, on the banks of the St. Croix, established Arcola Mills—a sawmill with aspirations of townhood. At its height in the 1850s, a few dozen people lived at Arcola Mills.
Though most of the original buildings are gone, the centerpiece of the Mower fiefdom has survived: a straight-laced, two-and-a-half-story Greek Revival house, built in 1847 and expanded in the 1870s. Placed on the National Register in 1977, the house is one of the oldest in Minnesota still on its original site—though a far from ideal one. By the 1990s, a century-and-a-half of groundwater intrusion had eroded the foundation and critically undermined the building to the point that the only way to save it was to construct a new foundation, basement, and water control system under the existing structure. Looking at the methods and materials used to build these systems can offer ideas for other old houses with chronic groundwater problems.
Designing the Dream
When Katherine Van Meier, the last private owner of Arcola Mills, died in 1991, she decreed in her will that a nonprofit organization should be created as the new owner of the house and its 53-acre site. She further stated that this organization should convert Arcola Mills into a retreat center and a museum honoring Minnesota’s lumber industry. While Van Meier left no money for these purposes, history-minded St. Croix Valley residents have formed the Arcola Mills Historic Foundation to carry out her grand vision.
In 1999 the foundation published its Historic Structures Report, laying out a comprehensive renovation plan. The exterior and first-floor public rooms will look as they did in the 1870s, but in most other ways the house is being fundamentally changed to realize Katherine Van Meier’s dream of a retreat center and museum. There’s a big new institutional kitchen, and the upstairs has been reconfigured as eight bedrooms with private baths to accommodate overnight retreats.
These ambitious plans faced a soggy start. When general contractor Rolf Dittmann of River Valley Restoration first inspected the house, he found plenty of trouble—mostly caused by water. The Mowers had proudly located their home on a raised bank, a site that afforded views up and down the scenic bluffs of the St. Croix along with numerous springs to power their lumber mill. They also had purposely allowed water to run right through the basement of the house and then into the river.
Dittmann’s inspection suggested that the Mowers probably used this basement stream as a crude sewage system. Consequently, free-ranging water had been infiltrating and rotting the sandstone foundation walls and wood structural members for 150 years. Some floors were as much as a foot out of level, leaving the house severely racked and on the brink of collapse. Dittmann determined that he would need to demolish and replace the foundation.
One of the board’s most far-reaching decisions was to place offices and the museum in the basement. To achieve this, plans called for increasing the ceiling height in the basement from 6′ to about 9′. This would be accomplished by excavating the basement 18″ deeper and by permanently raising the house another 18″.
A House Raising
It took Dittmann and his house-moving subcontractor several weeks to prepare the house for lifting. First they constructed temporary bearing walls in two places to stabilize the shaky structure. To provide bearing points at the rear of the house, they also added a temporary sill under the floor joists. There had never been a sill in that position; in the original construction, the joists had been set directly into pockets in the stone foundation. Dittmann and his crew also removed all lath and plaster from the house (much of it affected by racking). That significantly reduced the weight to be lifted and gave the timber-frame members a chance to naturally straighten and recover from racking as the crew took steps to stabilize the structure.
In the next phase, the subcontractor inserted four steel I-beams through the foundation under the first floor framing as bearing points for jacks. Two of these I-beams were 54′ long, running under the two main bearing walls near the center of the house. The other two I-beams were placed under the 1870s addition. These ran perpendicular to the first two because the floor joists in the addition are perpendicular to those in the 1847 house.
The house mover then deployed eight hydraulic jacks to raise the house. Each jack stood atop a cribbing tower—6″ x 6″ timbers stacked so as to spread the load on the concrete floor below. The jacking process took several days, with one man operating the jacks from a central control panel while others monitored the jack points for level. The operator could raise one jack at a time when needed or all jacks simultaneously. Dittmann says the jacking process proceeded very smoothly.
Finding Better Footing
After lifting the house, the crew demolished the old foundation and constructed a new one that rests on a continuous 24″-wide concrete footing around the perimeter of the house. Minnesota’s building code requires that footings be 42″ below grade to avoid frost heave. To accommodate a walk-out basement facing the river, the footings on that side were placed several feet lower than those under the rest of the foundation. In addition to the perimeter footing, the crew poured 36″ square x 12″ deep footings for the posts supporting the two main bearing walls of the 1847 house.
The foundation walls are core-filled concrete block with a code-required “bond beam” every 48″ of height. The bond beam consists of horizontal rebar lying in the notches of blocks specially molded for this purpose. Vertical reinforcement, composed of core-filled blocks with rebar, was placed every 6′ to 8′ along the wall. For added strength, reinforcing pilasters were placed at 12″ intervals around the three sides of the house that have taller foundations to accommodate the walk-out. Each pilaster is an 18″-square column of core-filled block with vertical rebar.
The foundation waterproofing system employs several elements. First, Dittmann sprayed conventional asphalt waterproofing on the outside of the block wall. Next came 4″ diameter perforated drain tile laid at the base of the wall’s exterior. Then, open-cell R-10 drainboard was applied to the exterior of the wall to conduct water directly into the drain tile. Limestone fill was laid around the tile. Finally, the crew landscaped earth in berms against the building. The berms slope into wide swales that drain surface water toward the river.
After constructing the foundation walls, Dittmann waited for a year. We wanted to see what conditions would be like in all seasons. We wanted to judge how much water there would be and how much the foundation walls would move due to frost heave.
Overbuilding the Basement
After his year of observation, Dittmann began excavating for a new basement floor. “When we got down to bedrock,” he says, “we found a spring near each of the back corners of the house—and each spring was producing about as much water as a full-on garden hose.” In response, he installed a drainage system proposed by a consultant: a drain tile running around the perimeter and another tile down the center of the house. Once this system was in place, Dittmann says he could see that it was insufficient; the ground was still soggy. So he was forced to remove the tile and start over.
At that point, he could find no one willing to specify what would be needed to truly dewater the site, so he decided to greatly overbuild. “We installed six 4″-diameter drain tiles under the house. They all feed into a single pipe that exits on the river bank.” He then poured crushed limestone around the drain tiles and covered that with a 2″ layer of sand. Dittmann says, “We know there will always be water under this house, but this system is keeping the water table below the level of the footings.
With all of the water and construction challenges he has faced, Dittmann maintains that his biggest problem has been monetary. “We totally run out of money every so often. At one point, we had to stop construction for nine months. You have to build a different way when you know you’re going to run out of money. You plan each step carefully so that, if the house has to sit that way for a while, it won’t adversely affect the later parts of construction.”Published in: Old-House Journal March/April 2003