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House gets a lift to alter the clay soil underneath

by: Sam Bennett, 
Todd Marchant, a subcontractor, and Carol Riggs stand in front of Riggs’ Lake Oswego home. Marchant was removing expansive soil from under the home.

Homebuyers usually find a few quirks, once they get settled in. A slow drain or creaky floorboard - things they missed in the excitement of getting a new home.

But for Carol and Ralph Riggs, there was a much bigger surprise right under their feet.

The Riggs' home on Woodside Circle in Lake Oswego was moving up and down, depending on the season.

The geotechnical explanation is 'high shrink-swell soils' - meaning that moisture in the soil under their home causes it to move as the moisture seeps in and evaporates.

The remedy is to lift the home and remove the expansive soil.

The Riggs bought the home in the spring of 2006, but didn't discover the problem until they started a renovation.

'We went to remodel the house and found one end of the house was two inches lower than the other,' said Carol Riggs, a Lake Oswego accountant and consultant. 'We couldn't even close the windows.'

The Riggs moved to Lake Oswego to be closer to their four children and eight grandchildren, who live, work and go to school here.

They had lived in Cedar Hills for 30 years. Their Lake Oswego home is in a planned development called Woodside Community Association. The development has a homeowners association and includes a pool, tennis courts and landscaping - for which association members pay a monthly fee.

Riggs said being in the development meant 'less work for us,' because maintenance on the roof and gutters of the home are part of the association benefits.

'It's the perfect spot for us,' said Riggs, as she looked at the home at 4385 Woodside Circle. 'It's our dream home.'

The couple bought the home, with the intention of retiring in it. When they bought it, they knew the three-bedroom home would need a remodeled kitchen, master bedroom and bath, as well as new windows and doors. But they soon realized there was no point in remodeling until they fixed the soil problem.

Kevin Foster of the Portland geotechnical firm Foster Gambee Geotechnical said the shrink-swell soil under the Riggs home is caused by the presence of clay minerals. The soil expands with moisture, lifting the foundation as much as a few inches and cracking it. The moisture in the soil does not change uniformly, causing 'differential settlement,' Foster said.

'It torques the framing and starts distorting the wall framing,' he said. 'That turns the normally rectangular window openings into a parallelogram. Then the windows no longer fit the frames.'

At that point, the windows won't slide easily up and down and doors begin sticking.

The problem was not identified by an inspector when the Riggs purchased the home.

'Sometimes, inspectors miss it,' Foster said. 'Most Portlanders don't have this problem, and that's why people are not savvy about it, because they don't see it very often.'

The Riggs have hired Portland attorney Dennis Elliott. Elliott said 'We're investigating it and trying to determine what the causes are and who's responsible.'

He declined to elaborate.

Meantime, the Riggs home has been lifted about 10 feet, to make way for excavators that are removing the bad soil. Foundation work should begin this week.

The new foundation will be on top of gravel, which will prevent it from cracking.

Emmert International was the contractor, which hoisted the home. Nine I-beams were used to lift the home and wooden 'cribbing' is used to support the I-beams.

'There have been a lot of sightseers,' said Scott Riggs of Riggs and Martin, Inc., a Milwaukie general contractor. 'The biggest challenge has been getting the equipment in and out of there.'

For Riggs and her husband, the six- to eight-week construction timeline will be worth the wait. She said they will be happy 'once it's done, back on the ground and remodeled. That's where we intend to spend the rest of our lives.'