Philadelphia West, Pennsylvania

R.J. Laverne can see the dangers with treehouses.

He can see how they can be damaging to trees, places where a person can fall "and land on his head," where that head also can be threatened by falling branches and where bad weather is a big problem.

That said, the manager of education and training at Ohio-based Davey Tree, says: "But treehouses are great places. I think our culture is so risk-averse we are avoiding many things outside. Treehouses are wonderful places for creative living."

That creativity can exist in treehouses that are self-made projects, those that are from professional specialists in treehouses or even in manufactured playsets that are nestled in wooded areas.

Bob Bocchino of Ohio Township near Sewickley spent about $14,000 eight years ago combining two playsets that he customized for a wooded area at the back of his property. He has even run low-voltage lighting for the rooms that are still popular with his three children, who now are 13, 11 and 9. Even the oldest, Aleksandr, still "loves it."

Amy Gennari from Aspinwall spent far less on the treehouse that is used by her three children "ALLLLLLL the time."

She adds the costs consisted of "the sliding board and the lumber. And that was 12 years ago."

Similarly, Mark Paff built a two-level treehouse that is about 22 feet high for "no more than $1,000" eight years ago.

But Daniel Goldman from Yardley, Bucks County, has a treehouse he plans to air-condition. He has an 8-foot-by-8-foot backyard retreat built for his two children. It also was built as a way of gaining some privacy in his backyard. It cost probably near $10,000, he says.

But it is more than a kids' place.

"Oh, sure, I've hung out there," he says. "I love hangin' in the treehouse."

An answer amid the leaves

Treehouses go back to, well, most likely to when man lived in trees.

Such long-lasting popularity probably is the reason treehouses are dealt with by professionals such as Dan Wright, a carpenter who also is an arborist and heads a treehouse-building firm in Chester County. His Tree Top Builders has been in existence nine years and has built around 150 structures, most between $5,000 and $60,000, but one that went to $250,000.

There also are retailers who sell children's playsets that are not meant to be placed in trees, but create backyard settings that mimic the experience.

Adam Curry from B.E.A.R. of Pennsylvania says the reason is simple. The playsets all are tested and rated to bear weight and be safe in their designed uses, not to be put in trees. That use would add an element of uncertainty that manufacturers or retailers such as his Richland firm would not want to touch, he says.

He says customers seem to know that, too, and he has "never had someone ask for a treehouse."

Similarly, Patty Toner from Lilliput Play Homes in Finleyville says her customers do not look for a treehouse, but simply want a playset that can be stood on posts to give a feeling of getting away to that special, removed place.

Bob and Pamela Bocchino were looking for such a site for the wooded back of their Ohio Township property. He said he couldn't find a treehouse builder, and decided he could accomplish his goals with playsets he found at Lilliput. The project was done by combining two play homes and then customizing them with swingsets and a picnic table in one deck-like setting.

Amy Gennari says when she, her husband and two children moved into their big Aspinwall home, it still had two tenants in it, so they wanted to add a recreation spot for their kids.

So it became and so it still is, she says, now for three children who are 16, 14, and 11.

When they built the treehouse, they "just sort of winged it," Gennari says, but her 14-year-old son Brian "has become so much of a treehouse expert," he built one at her family's home in Vermont "that is much more dramatic that this one."

Safety for trees, humans

Davey's Laverne say staying alert to the health of the tree is vital for any house put in it. That means one of the key elements is making sure not to traumatize the support structure.

"The day you put a nail or screw into a tree is the day that tree will be its strongest," he says. Laverne goes on to say that action may not kill the tree, but it won't let it become any stronger either.

Wright, an arborist as well as a carpenter, thinks Laverne may be "overstating" it a bit, but agrees metal could cause a problem, particularly with weak trees.

But he does agree the better idea is to keep the treehouse standing on its own legs "to minimize the damage done."

Gennari says they had a feeling about that in their project and used "exactly one nail" in the tree. It sits in the tree, but on its own posts.

Laverne says the type of wood in the tree also is important because denser wood would support weight better. He also advises being aware of the quality of the tree's canopy because that can indicate health and also be a warning about the risk of falling branches.

In any wind or harsher weather, he says, it is wise to get treehouse users away from their outside perch right away.

Despite all of the potential risks, he sees, Laverne still is an advocate of this form of branching out.

"Treehouses are just great places," he says.