Green mildew on vinyl siding

Mildew on Vinyl Siding
Mildew on Vinyl Siding

Q.  I have green mildew on my vinyl siding. I used a 2200 PSI power-washer and was not able to remove all of the mildew. Is there a solution I can use to get the rest off without damaging the vinyl siding or do you have any other suggestions?

A.  I assume that you used a weak mixture or didn’t use bleach at all in your power-washer. Power-washing any mildewed surface without a strong bleach solution may remove some surface pollutants but it will not remove the mildew. If the mildew is found on small and easily accessible areas, you will have more success if you do it by hand because it is not easy to have the right concentration of bleach mixed with the water going through a pressure washer.

Wear heavy rubber gloves, mix fresh Clorox bleach and water in equal quantities in a 5-gallon plastic pail, and apply the solution with a soft bristle brush so as not to scratch the siding. If you add a cup of TSP or TSPPF detergent (buy in hardware stores) per gallon of the solution, you will also remove any other stubborn stains that plain water from the pressure washer didn’t get. If you only use a bleach solution, do not rinse it. But if you use detergent, you will need to rinse the treated areas.

Be sure that you cover vegetation with plastic after soaking it before and after the washing.

Painting cedar-shingle siding

Q.  I need a lot of painting tips: I’m preparing to paint the exterior of my 95 year old cedar-shingle house and am not sure if the best way to go is with latex paint or stain for the best adherence and durability, and if the entire surface should be washed first before scraping.

Since its been twenty five years since the last paint job, but still good on north and east sides, should the entire house be primed or just where bare spots?

Also, to eliminate air migration, should I caulk the vertical spaces between the shingles and window trim or let it stay clear for drying?
Is there any additive that could be added to an exterior latex paint that would increase its gloss quality? Thanks.

A.  If the north and east sides are still good, and you know whether paint or stain was used, you should use the same coating to make sure everything matches.

It is best to powerwash the entire siding to remove all pollutants; this would also remove any poorly adhering coating. Some scraping may be needed.

If you decide on staining, there is no need to prime any of the surfaces. But if you choose to paint, you should apply an alkyd primer to the bare areas before applying a latex final coat.  Apply a new coat to the cleaned shingles over the good north and east sides so everything will match.

Choose a high gloss exterior latex to achieve the shiny look you want.

Do not caulk the spaces between the shingles; let the shingles breathe and expand and contract with the seasons.

Re-siding an old farmhouse

Q.    My husband and I recently purchased an 1820 farmhouse and plan to put in new windows, plus new pre-primed cedar clapboards. We will use the Home Slicker with Typar. Our question concerns the following: The house is built with vertical planks, two to three inches thick, which are essentially slabs of wide trees. There are gaps between the planks, as they are irregular in shape. Do you suggest that we cover these planks with plywood before using the Home Slicker?

A.    There is no need to use plywood over the planks unless the gaps are very large; anything up to an inch should not matter. The Typar is a windbreaker and the gaps will help the house breathe if there is no air barrier/vapor retarder on the inside of the exterior walls.

You haven’t mentioned insulation or the inside finish. Is there any insulation on the living space side of the planks? If not, and there is no way to do so from the inside, you may want to consider installing 2-inch thick rigid insulation over the planks followed by 5/8th-inch CDX plywood sheathing onto which the Typar/Home Slicker can be stapled. Even though clapboards should be nailed onto studs, since you will providing a rain screen behind the clapboards, they should be OK nailed to the plywood.

Repainting a house that lacks vapor retarder

Q.   In an earlier post, you commented on a house with wood siding that paint would not adhere to, peeling off within two years, probably because it lacked a proper vapor barrier on the warm side of the walls. This is an issue we are aware of in our home. We are about to repaint our home and I wondered if you could offer any suggestions as to how we may best deal with this.

In my search for useful suggestions on this subject (my thought process hoping for some sort of advanced product to use in our painting) I ran across a product “permanent coatings,” but they were in Vancouver. I didn’t know if that could be an answer or if it is even sold in the states. Nevertheless it made me even more curious as to whether or not there may indeed be a technologically advanced product out there that could bring us salvation!

A.  I do not know anything about the product you mention, but I am very wary of the hoopla about some products that claim miracle solutions. Moreover, this coating is for exterior application in lieu of regular paint. It does not solve the convection and diffusion of moisture into the exterior wall cavities, which are the cause of the problem.

A vapor barrier is needed on the warm side of the exterior wall to prevent moisture from migrating into the wall cavities and causing major paint peeling, and potentially worse problems.

The most important thing to do, to provide an effective barrier to moisture convection into the wall cavities, is to check for cracks and minor openings on walls and ceilings; where different materials meet, such as window and door trim and baseboard; around electrical ceiling fixtures, switch and receptacle boxes. These openings, however minor, should be caulked.

Hardware stores sell closed-cell gaskets that are installed under the cover of switches and receptacles.
The walls can be painted with B-I-N, followed by your choice of finish paint or two coats of a low-perm paint.

Reducing maintenance with new siding and windows

Q.  You have written that we should take the cedar shakes off before re-siding. Would it be more insulated if the siding is put over the shakes? As a widow, I would like to eliminate maintenance. I would like to replace the windows also so there is no upkeep. Vinyl or aluminum?

A.  Cedar-shake siding is quite irregular and makes things difficult when trying to apply vinyl siding smoothly. You will get more insulation if the shakes are removed, and 1-inch thick rigid extruded polystyrene (XPS) insulation is installed directly over the sheathing.

If your question is whether to have vinyl or aluminum siding put on, the decision is very much up to you and the local market. Vinyl siding represents the bulk of the installations nowadays and, when properly installed by experienced workers, it is a good and long-lasting, maintenance-free siding.

So is aluminum, although it is not as popular as it was decades ago, and you may not find it available in your area. I would urge you to insist on XPS insulation (blue, grey, green or pink) instead of accepting the type of thinner fold-up material some installers will offer you; it is not as effective an insulation, but the dealers like it because it goes up faster.

The windows are also somewhat of a local matter — whichever is most popular in your area: aluminum or vinyl, just make sure that it is a top-quality product. I have worked with clients who had bought lesser-quality vinyl windows, and were beset with cold-air infiltration as the vinyl shrank in cold weather — a tremendous loss of energy. The windows may have looked like they were tight in the store, but they did not perform well once installed.

It is recommended that you get three estimates from reputable contractors, but the most important thing you can do is choose a contractor who has an excellent reputation for quality work, presents you with a clear and detailed contract that stipulates the type of material to be used, a start and finish date, and who follows up quickly on any punch list items (they are almost unavoidable in construction.) Ask for several references of people whose jobs were done recently, one and two years ago (two names for each category), and call them.

Keep in mind that choosing the lowest price is often not the best in the long run.

Do not agree to pay anymore than 10 percent at contract signature with the balance due at satisfactory completion. Anyone who asks you for half or more of the money “to pay for the materials” should arouse your suspicions. Also check with the Better Business Bureau and the consumer protection division of your state’s attorney general to see if there are any unresolved complaints against the contractors you are considering.

Cleaning and re-treating cedar clapboards

Q.  The cedar clapboards on our house were installed about 23 years ago. A year or two after they were put up, a bleaching agent was applied to help maintain the color. I have no idea what product was used. The south-facing clapboards have become quite dark.

I am wondering if another coat of something should be applied to keep the clapboards from drying out and cracking. If so, what should I use, and how is it applied? If it is sprayed on, do I need to protect the plantings at the base of the house? Do I need to protect the windows which are vinyl-clad?

A.    If the clapboards have not received any new treatment for the last 20 years or so, it is a good idea to do so this coming warm season. Buy Oxy-Boost and Deck & Patio Cleaner from Mix them in equal parts in warm water and wash the siding with a stiff brush. Rinse with a garden hose when done.

Before spraying the solution on, you should soak the plantings and cover them with plastic.

Hose the plastic off, remove it, and soak the plantings again. Once the siding has thoroughly dried, apply Amteco TWP Series 101 Cedartone Natural or Series 1500 Low Voc Cedar, slightly darker and less orangy than 101 Cedartone. Considering how long it has been since you applied a wood preservative on the clapboards, they might need two coats. You can apply Amteco by brush or by spraying it on. Be sure to follow the directions on the Amteco container for either brushing or spraying.

Getting best value when replacing siding and roofing

Q.    I am soon having my split-level house re-roofed, while also installing new siding and gutters. The enclosed picture (below) shows my home, which faces South.

904 Ironwood

When the contractor strips off the old (original) aluminum siding, he will be injecting Airkrete into the wall cavities all around the house (also the brick). The lower roof on the right (East) side of the house covers a cathedral ceiling which is over the front living room and a few steps up, to the dining room. The far North side of this lower roof covers the kitchen which has a regular 8-foot ceiling.

The contractor will also be injecting the Airkrete into the cathedral ceiling, and adding additional blown-in insulation above the kitchen. There are two can vents over the kitchen area. Airkrete will also be injected into the walls and ceiling in the attached garage.

On the top roof, you can see the front gable vent, there is also a matching gable vent on the North side of the house. There are also four can vents on top of roof. I have a 1500 cfm. powered attic fan on the East side of the top roof.

Fifteen years ago, I re-insulated the attic using Owens Corning R-25  batts (I think it was called Easy Touch. Has a thin sheathing all around the batt). First layer laid in the floor joists, 2nd layer laid perpendicular over 1st layer.  I also installed soffit vent chutes in all rafters at the soffit area.

For the siding, my contractor will be installing Mastic Structure foam-backed Dutch lap siding over Tyvek housewrap. For the roof, he will be installing GAF Timberline Architectural shingles with 6 feet of ice and snow shield.  The 4-inch gutters will be replaced with 6-inch gutters and downspouts. The wood railing and posts above the garage will be replaced with Azek board material.

I would greatly appreciate your opinion and suggestions to make sure this is being done correctly so I can get the most value for the money I am investing in this major renovation. My location is a Northwest suburb of Chicago. Thank you.

A.    Everything you are having done seems fine. The only comments I would offer are as follows:

  • Power roof vents have serious drawbacks. Unless there is enough net, free ventilation area (NFVA) in the attic itself to satisfy their CFM rating – which is seldom the case – they will draw conditioned air from below. This is a waste of energy both summer (assuming that you have central air-conditioning) and winter.
  • A better approach is to insulate the attic as you did, and make sure that you have adequate passive ventilation by means of continuous soffit and externally-baffled ridge vents. You also must have an uninterrupted air flow between the soffits and the ridge.
  • However, if there are no moisture problems in the attic, it would indicate that the two gable vents are doing the job, in which case there is no need to change anything.
  • Roof can vents are not effective, and it is best to eliminate them in favor of the passive ventilation described above. But, as mentioned above, if you have no problem, don’t change anything.

Otherwise, you are doing fine. I am glad that you are replacing residential gutters and downspouts with commercial ones; it’s a winning combination.

Re-siding a house with either aluminum or vinyl

Q.    My wife and I plan to re-side our 50-year-old house. It currently has wooden shakes and we are considering either aluminum or vinyl siding to remove the need for painting. What type of siding would you recommend?

In your recommendation, could you identify the desired features of the siding and address such concerns as temperature variation, wind, repair and maintenance. How would I avoid damaging either type when an extension ladder is placed against the siding?

Since my wife has seen and likes the shingle-type vinyl siding, I wonder if that pattern also comes in aluminum.

A.    Either aluminum or vinyl is fine. The popularity of each is often regional. Vinyl is better in an industrial area but it can break and crack if struck during freezing temperatures. It expands and contracts less than aluminum with temperature changes. If properly installed, wind should not be a factor with either siding.

You will have more choices of patterns with vinyl than you will with aluminum. And do not lean ladders against either, as it will damage them. You should seriously consider installing 1-inch- thick extruded polystyrene rigid insulation (XPS) under either siding on a smooth sheathing. This is your best chance to increase the R-factor of your walls.