Home repair: Try spray-on options to remove unwelcome roof guests

Q. I have various forms of mold and algae growing on a shingled roof facing east over my kitchen and mudroom. I have not had any luck finding a contractor or roofer to come take a look.

I am wondering if there is a spray that will kill the molds and algae and not stain the roof or painted shingles.

A. Thank you for the many photos you sent. They do show a combination of algae, moss and lichen.

There are various preparations that can be sprayed on the roof shingles. Spray & Forget, www.sprayandforget.com; Wet & Forget, www.wetandforget.com; an oxygen bleach, www.ecogeeks.com; Stainhandler Roof & Deck Cleaner, www.stainhandler.com; as well as pool chemicals.

You can also make your own chlorine bleach solution by mixing equal parts fresh Clorox and water. Use a garden sprayer to spray the roof on a windless day and do not overspray: One gallon takes care of 50 square feet of roof. But before spraying the roof, soak any plantings below the roof, cover them with plastic and rinse the plastic and the plantings when done. If you have metal gutters, run water through them while there is some runoff from the roof.

Most of these products will take some time to remove the growth, while some promise instant success.

Have a contractor install zinc strips just below the ridge cap to give long-term protection from these unwelcome growths. Stainhandler sells zinc strips, but 50-foot rolls can also be found in some hardware and big-box stores.

Q. We purchased a cabin in northeast Pennsylvania built in the early 1960s. It has not been used for over 10 years. It is a block 1-1/2-story structure, built on a footer, with a crawl space, 20 feet by 24 feet. The crawl space is vented with three vents the size of a block each. There were no gutters on the building. The terrain is on a slope, so part of the main floor is below the ground level. We have gutted the inside down to the block.

Parts of the first floor are very weak. I suspect this is from the dampness getting under the building. We replaced the roof and added gutters to get the roof water away from the building. I doubt the foundation was drained, so we are thinking of doing that, pressure washing, then coating the foundation with a product you recommend. The floor joists are run into the block outer walls for support. We will remove the entire first floor to replace it, salvaging any joists if possible.

How would you suggest that we rebuild the floor? I do not like the idea of the floor joist going into the block. We would rather support it from the footer if possible. Should we use treated lumber as a band board and also for the joists? Should the crawl space be vented? If you suggest putting plastic on the ground in the crawl space will mold grow under the plastic?

For insulation purposes, we are planning on covering the block with Styrofoam, then studding the walls and insulating with fiberglass. Should the Styrofoam be behind the band board, and also be in the crawl space? Is there a book you recommend with this type of construction information?

We will use the cabin year-round, but will not live there permanently. Thank you for any advice.

A. Instead of coating the foundation, once you have bared it, apply 6-mil plastic against the blocks and cover the plastic with 1-inch-thick Styrofoam rigid insulation from the footing to its top.

Then install the foundation drain you want to put in as follows: Pin filter fabric (often called landscape fabric) on the outer side of the trench. Lay a perforated PVC pipe over a 2-inch bed of crushed stones and cover it with more crushed stones to grade if you do not intend to have plantings. This would take care of surface water as well as any subsurface water. If you want to grow grass or plantings, stop the stone backfill one foot below the eventual grade, fold the filter fabric over the stones and add soil to grade, sloping it away approximately two inches per horizontal foot. This backfill system does away with any concerns about frost pushing the walls in.

For the floor joists, you can set a pressure-treated (PT) band joist supported by PT posts against the blocks. Install the PT joists with U-grips of the proper size.

If you cover the crawl space floor with 6-mil plastic, today’s thinking is not to vent the crawl space, as it introduces moist air in the summer, which is not desirable, and makes the floor cold in the winter. Keep the vents in, but close them and give the crawl space the smell test every once in a while to make sure that it does not smell moldy. Don’t worry about what happens below the plastic.

Build the walls as you suggest and insulate them with fiberglass.

I don’t know of a book that would detail what I recommend other than mine: “About the House with Henri de Marne,” which answers many homeowners’ questions received over the last 30-plus years. It is available in some books stores or directly from Upper Access Books and Software, www.upperaccess.com, or (800) 310-8320.

Q. We would like to use a portable air conditioner in an upstairs bedroom.

The A/C is designed to be vented out of a double-hung sash. The room has crank-out windows, so I think it needs to be vented through the wall. The A/C has a 5-1/2-inch diameter exhaust vent, so a standard 4-inch diameter vent is not an option. Is there a 5-1/2-inch vent available or do I have another option?

A. Check out hardware stores and big-box stores. Lowe’s has 6-inch metal ducts that should work. You can insert the A/C exhaust duct into the 6-inch duct and stuff a plastic backer rod of the right diameter between the two. A backer rod can be bought in the same stores; it is used to fill cracks so they can be properly caulked.

Q. I am looking for guidance or information on what type of material to use on my house. I redid the roof about 20 years ago with 30-year shingles, which have not held up very well. I am thinking about using corrugated metal this time hoping that it would last longer, but my better half is not fond of that idea. He thinks that we might have a problem with snow sliding off and wonders about walking on the metal. Twice a year we hitch sail covers to anchors over the back deck and must walk on the lower back roof. In your opinion, would shingles be preferred over corrugated metal?

A. Your experience with asphalt shingles is typical; most of them do not last the advertised longevity.

Corrugated metal roofs that are properly screwed on with the right fasteners can last a long time if they are factory-coated in various colors. However, metal roofs can be slippery, especially when wet, but that also depends on the pitch of the roof. Snow does not slide off these roofs easily because of the fasteners, but it can do so if the roof is steep. Snow guards can be installed.

Your photo does not show the deck, so I can’t tell whether or not there could be some difficulty.

Q. I currently have IKO shingles (three-tab, 25-year shingles) on my roof, which failed prematurely. I need to replace the roof, but all the local dealers in the Morristown, Vt., area sell only IKO. One vendor had Certain Teed, but it has since quit carrying them.

In the past, I have read your articles and you (were) are vehemently anti-IKO. Which brand of roof shingle, in your opinion, should I try to find and buy? I know that I will definitely use the architectural type of shingles.

What do you recommend for the valleys? One contractor wanted to put down steel, because of the difficulty of weaving architectural in a valley. Another would shingle over the valley and then bring the other side to a straight line in the middle of the valley, not wove. I know I did not describe this method very well. Both contractors would ice- and water-shield the valleys.

A. The IKO shingles, like many others, have failed long before their claimed longevity. Several shingle manufacturers have settled class-action lawsuits filed against them by homeowners. My feelings about IKO derive from direct experience with its refusal to settle legitimate claims to the point of fighting these claims in court at a greater expense to it than settling the claim.

We had 25-year IKO shingles on our roof, which failed in 14 years. Knowing of its refusal to settle any claims, we didn’t bother to file one; the aggravation is not worth it.

The history of most asphalt/fiberglass roof shingles is dismal; it’s like the Wild West out there, and I am at a loss to suggest any brand. Even the brand we replaced the IKO shingles with has a history of fighting legitimate claims.

Fiberglass shingles seem to hold out better than organic shingles, but it depends on the brand and when they were manufactured. The 20-year Bird shingles I put on my former house in 1979 lasted 27 years before I replaced them to sell the house.

I would never recommend either woven or closed-cut valleys, the latter being what one of the contractors is specifying. They are seldom done right and, because they drain two roof planes, they wear out much faster than the rest of the roof.

Metal is the way to go, but there are steps to follow as well. The metal should be of heavy gauge — not coil stock — installed only in 6- to 8-foot lengths, nailed only at the top with clips along the sides to allow for thermal movement. It should be square-cut at the bottom to prevent water from running down the siding.

An ice and water protective membrane is essential at all eaves, valleys, roof perforations and where a lower roof ties into a wall.

Ÿ Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via email at henridemarne@gmavt.net. His book, “About the House,” is available at www.upperaccess.com and in bookstores.

© 2012, United Feature Syndicate Inc.