A cement wall around a yard might be a not-so-subtle message to stay away. But for Marnie Dowd, mother of three, that formidable wall is only a sound barrier.

And to prove she's not trying to wall off her Healdsburg neighbors, she punched out two wooden windows for the possible friendly "yoo-hoo."

The wall also provides the backdrop for a dramatic modern garden, just one distinct space in a property she and her husband, Ross, carefully planned out to accommodate the needs of a multi-generational family that soon will include her elderly parents.

There are places to play, places to entertain, a full-size lap pool, a massive wrap-around screened-in porch and even a Japanese garden off the master bedroom where two busy parents can decompress. Oh, and two houses.

As further evidence of Dowd's friendly-neighbor policy, she invited the public to stroll through her many-layered landscape during the Sonoma County Medical Alliance and Foundation's 23rd Annual Garden Tour on May 17.

The tour offers a peak into six very different Healdsburg gardens, from bird and butterfly sanctuary surrounding a 1926 bungalow to a French contemporary-style garden complete with petanque court.

The Medical Alliance Tour is one of a number of home and garden tours coming up in the North Bay. It's a springtime tradition, when people get a rare chance to go beyond the gates, fences, walls and doors of private homes and gardens to see what other people are doing with their living space, both inside and out.

Think HGTV, but better. These are people working within the architecture, climate and tastes of the San Francisco Bay Area.

The season kicks off May 4 with the Healdsburg AAUW Homes Tour. The tour includes six homes, all within a short radius of the plaza. They include a renovated 1938 Tudor cottage, the spectacularly appointed Ivy House on Center Street, featured in many magazines and home to designer Myra Hoefer, and a new house built on the site of a former boarding house.

New owner Kim Nordmo, an investment manager, fell in love with this new home, designed by Gerda Engelbart, that is packed with modern comforts but looks like it's been there for generations. The 3,200-square-foot home incorporates recycled wood from the original building.

Other tours coming up in the months of May and June include an architectural tour of The Sea Ranch and Gualala on May 10, put on by the Soroptimists of the Mendocino-Sonoma Coast; The Garden Conservancy's Open Gardens Day in Mendocino County, featuring three private gardens in Mendocino, Fort Bragg and Boonville; and The Eco-Friendly Garden Tour May 17, sponsored by the Sonoma-Marin Water Saving Partnership.

The season ends in June with Food for Thought's Western Sonoma County Home & Garden Tour June 8, Resorts in Bloom June 13 and 14 benefiting the West County Health Centers and the Sonoma County Master Gardener's Bloomin' Backyards June 8 featuring Sonoma Valley gardens.

The tours are more than a chance to ogle; they're an opportunity to see how other homeowners tackled design dilemmas, apportioned space and incorporated materials.

For Marnie and Ross Dowd, the challenge was how to create ample space for a variety of different needs, including a house big enough for three young kids and a separate house for her aging parents, on a double corner lot of less than one acre at a fairly busy residential intersection.

The concrete wall, beautified with elements like the wood windows and a hanging vertical succulent garden, allowed her to use space for private outdoor living that otherwise would have been too exposed and noisy. She said she was inspired by the courtyard of the Hotel Healdsburg, where she spent hours reading with her kids while her house was being built.

Dowd knew she wanted a home reminiscent of the brownstones she grew up in back in Chicago. But when designing the two-story house, she happily sacrificed square footage inside for more yard and a massive wrap-around screened-porch room that looks out over a carpet of realistic-looking artificial turf for the kids to play without dragging mud in.

"The California weather is so amazing," she said. "I love to be outside as much as I can. I love the idea we have a lot of nooks and crannies outside. I joke and tell peope this is the house where the kids never come inside."

<i>You can reach Staff Writer Meg McConahey at meg.mcconahey@pressdemocrat.com or 521-5204.</i>