Ask This Old House

Removing and preventing moss, algae and lichen from a roof
General contractor Tom Silva helps a homeowner prevent moss, algae and lichen from growing on his shade-covered roof. Tom explains that these types of organisms can hold moisture against a roof's shingles, thereby shortening the life of the roof. After installing roof brackets and platforms on which to work, Tom installs strips of zinc flashing near the ridge. When it rains, the zinc will dissolve into the rainwater and wash over the roof, preventing future organisms from growing. After installing the zinc strips, Tom kills the existing moss, algae and lichen by applying a mixture of bleach and water with a garden sprayer.

Where to Find It
Zinc strips manufactured by:
Shingle Shield
800-942-3004

Ladders, roof brackets and aluminum planks manufactured by:
Lynn Ladder & Scaffolding Co, Inc.
800-596-6717

Bleach and garden sprayers are available at your local home center.

What is it?
The guys try to guess the intended purpose of an unusual-looking object.

Where to Find It
Tom shows an antique device used for forming cardboard egg cartons. It was sent in by viewer Michael Heydenburg of Jersey City, New Jersey. Thanks, Michael!

Repairing a leaky water valve
Up in the loft, plumbing and heating expert Richard Trethewey shows host Kevin O'Connor how to repair a leaky faucet by replacing the faucet's washer and valve seat. He first shows how to remove the handle using a tool called a "handle puller." Once the handle is removed, Richard exposes the valve's worn out washer and retainer ring. He also shows the valve's "seat" and removes it using a special tool called a "seat wrench." Once the worn seat is removed, it can be replaced or re-milled to improve the seal between the washer and the seat.

Where to Find It
Valve parts are available at your local home center or plumbing supply house.

Planting shade-tolerant ground cover under a European Beech tree
Roger helps two homeowners plant ground cover under a century-old European Beech tree that is creating too much shade to grow a lawn. Roger begins by having the homeowners carefully remove all of the weeds underneath the tree. He then creates a planting bed by putting a 4 inch layer of compost, sand and topsoil around the base of the tree. Next, he spreads some fertilizer into the new soil by hand and rakes it in. Roger shows three different types of groundcover that he intends to plant: Epimedium Rubrum, Tiarella Cordifoli, and Waldsteinia. Roger divides the planting space under the tree into six sections and puts 20 plants of each variety into each spection, spacing them 12-16 inches apart. Before planting, Roger takes each plant out of its pot and loosens the roots. After planting, Roger waters everything and recommends spreading an inch of pine bark mulch to conserve moisture and prevent weeds from growing.

Where to Find It
Groundcover plants were provided by:
Gold Star Wholesale Nursery
1265 Massachusetts Ave
Lexington, MA 02420
781-861-1111

Other assistance was provided by:
Bartlett Tree Experts
800-969-5990

Matthew R. Foti Landscape & Tree Service
30 Fairbanks Rd
Lexington, MA 02421
781-861-0505