Ask The Experts

Exterior Finishes

I have some fairly significant cracks in the brick exterior walls of my house. The cracks start at the top corners of the windows on each end of the house. What is causing this and what can I do to stop it?

Cracks in exterior brick walls that start at the tops of window or door openings are most often caused by swelling of the steel lintels that support the brickwork above the openings. The lintel is usually an L shaped piece of steel which provides a shelf for the brick to rest on as it spans the opening. If the bottom flange of the steel lintel extends too close to the face of the brick, or is otherwise exposed to moisture, the steel will rust. As significant rusting occurs the metal expands. The slow expansion produces enough force to lift the brickwork that is above the window or door openings. This causes cracks to appear as the bricks are lifted up off the masonry on either side of the openings. These cracks are a very common occurrence, and usually do not result in major damage. However, every effort should be made to protect the steel from moisture, including caulking and painting the steel and possibly the brick. It may be very difficult to determine the actual source of the moisture, which could also be condensation from water vapor moving through the walls from the interior, as well as wet masonry due to rain. So be sure to take steps to control any excess moisture in the house which might be contributing to the rusting. In the worst case, as the rusting continues and the steel begins to seriously deteriorate, it may become necessary to replace the lintels. This can be a very expensive proposition if several window or door openings are involved. Being proactive now to ensure that the steel stays dry may save a large expense later.

In spite of the fact that our house has good air circulation all around, the vinyl siding on the north side develops a green pond-scum like growth in wet weather. What can we do about this? Is there a product that we could spray on the siding to prevent this growth?

The green discoloration is caused by a common algae that finds the vinyl siding on the shady north side of your house to be a suitable habitat for growth. It is not harmful to the siding, but does provide a poor appearance and can be a nuisance to remove. This algae is common in shady environments in nature, and often grows on other exterior materials and finishes around the house. Any overhanging trees or shrubs can aggravate the problem, but are not necessary for the algae to grow. Washing with a mild detergent solution, such as Spic and Span, and a long handled brush is usually sufficient to remove the algae from vinyl. Wet down the entire wall first, apply the solution with a garden sprayer, and clean from the bottom up to prevent streaking. Hose down the wall thoroughly when done. Power washing, strong cleaners or chlorine solutions are not normally necessary and may be harmful to the siding or any plants below. For a list of vinyl cleaners specific to various other stains we suggest visiting the Vinyl Siding Institute website at Search “vinyl cleaners.”

Keeping the algae off of the siding for the long term can be more difficult. There are products that claim to be able to resist algae, including vinyl renewal products that contain antimicrobial polymers. We do not have any personal experience with these to know what does or does not work. If our readers have used any algae resistant coatings that they have found to be particularly successful we will forward the information. If you experiment with any such applications we recommend that you try a discreet, out of the way area first, since these products are likely to affect the sheen of your vinyl. If you choose to use a vinyl renewal coating, you will be committing yourself to applying the product on at least one full side, and possibly the whole house, to ensure an even appearance.

I am interested in buying a house that has EIFS on the exterior. I am aware that there have been problems with this product. Can you explain what can be done to prevent any problems?

EIFS is the acronym for Exterior Insulation and Finish System. It consists of a stucco finish applied over a foam insulation board and has been around for a couple of decades. The product has been very popular in other parts of the country, but is seen more often locally in commercial buildings. Part of its popularity is that it provides a clean masonry-like appearance and can be sculpted to reproduce classical exterior architectural details.

The primary problem is that any moisture that gets behind the foam board insulation can become trapped inside the wall, cause rapid decay, and huge repair costs. A class-action law suit was initiated in the 1990’s, and considerable redesign and improved installation guidelines were developed at that time. The biggest changes included the requirement for a water resistant membrane and a drainage mat between the foam board and the wood wall sheathing. This allows any water that gets behind the foam to drain out the bottom without causing any harm. Even so, the installation must be done extremely carefully, and all flashing details around windows and doors, roof intersections, etc. are critical. The manufacturers now provide highly detailed installation guidelines to minimize errors.

Chances are, if the house was built before the mid-90’s, there is no drainage mat or secondary water intrusion barrier, greatly increasing the likelihood of problems. In any case, it is wise to have a very thorough inspection of the installation, and it may be appropriate to hire an inspector with a moisture meter to more intensively evaluate the integrity of the exterior finish than would occur during a standard home inspection.

I have a 15 year old vinyl sided house with wood trim. I am finding that a lot of the wood trim is rotting. What can I do to stop this?

There are several reasons why this wood is decaying, involving poor control of moisture. Most of the trim wood being used in recent construction is soft white pine. This wood has low resistance to decay, and must be kept absolutely dry. One option is to replace the wood with cedar, which has much better decay resistance. However, it will remain important to keep any new wood dry by preventing any water from seeping through the exterior finishes. In a house that is wood sided and trimmed, we do this for the most part by keeping the finishes well caulked and painted. Vinyl siding, on the other hand, cannot provide a water tight seal. It is designed, and should be installed, to readily shed water, but because it expands and contracts significantly, it must be installed loose and can’t be caulked to provide a seal. When water gets behind the vinyl, which is inevitable, it should be able to drain back out the bottom. Felt paper or a house wrap should protect the wood sheathing behind your siding as this water drains. Unfortunately, the wood trim on your house traps the moisture between the sheathing and the trim, causing decay.

We often find that the response to this problem is to simply wrap the face of the wood trim in aluminum. Unless other corrections are made, this will only compound the decay, by further entrapping the water. Presuming that a house wrap or felt paper is installed directly behind the vinyl siding, before each piece of decaying wood is replaced, an aluminum drip cap should be installed along the top of the wood. This “flashing” should slip up behind the vinyl siding directly above the wood trim, and more importantly should also slip behind the house wrap above the trim, and form a cover with a drip edge over the top of the wood to direct water out of the wall assembly. If there is no house wrap directly behind the siding, complete removal of all siding and trim would be necessary for correction of the problem.

The wood casings on the exterior of several of my windows are decaying badly. What should I do to stop this?

You don’t say the age of your house, but we’ll wager that it was built since 1950. Modern wood exterior trim, called brick mold, measuring roughly 1 ¼ inch by 2 ¼ inch, generally deteriorates much more rapidly than the older square cut 5/4 by 4 inch wood trim found on earlier homes. Modern wood casings are miter cut in the upper corners, which directs water into the grain of the wood, are often finger jointed, meaning built of numerous small pieces that allow water entry, and are generally installed without drip caps at the head casings. In addition, we suspect that the newer second growth wood we use today tends to be much less rot resistant than the older wood species found on earlier homes.

Decaying wood trim should not be ignored, because while the trim can be easily replaced, the wood sills and jambs adjacent to the casings cannot, and will be next in line for decay if it is not stopped. These parts are integral to the window or door and are likely to require the replacement of the entire unit for correction. Decayed wood can be filled and patched, but this is unlikely to last more than a few years. We recommend that new wood be installed. The new casings should be primed on all sides before being installed and should be well sealed, painted and caulked. Preventing the paint from peeling or wearing out, and repainting as necessary will go a long way to preventing decay in the first place. Another option is to aluminum wrap your trim, but this must be very thoughtfully done and maintained. If water gets behind the aluminum it will be trapped and the decay will be accelerated. We have found severe decay hidden behind aluminum trim wrap on many homes in our area. Another way to help prevent decay is by extending your roof overhangs and maintaining your gutters. This will help prevent splash damage to your trim. But regular inspection and maintenance is the key to ensuring the longevity of your wood trim.

When I pulled a piece of the aluminum siding off my house, I noticed that the fiberboard directly behind the siding was quite wet. Why is this getting wet, and is this normal?

You have asked a very important question about an issue that may negatively affect many homes over the long run. It is quite likely that the source of the moisture behind your siding is not leakage, but rather condensation. We generate large amounts of water in our homes as we cook, shower, breathe, water plants, and operate humidifiers. Warm air holds the moisture very well, but cold air does not. As the moisture moves from the warm house toward the colder dryer outdoors through our walls it reaches the dewpoint and condenses. There are three ways to reduce this problem. We can reduce the amount of moisture we produce, we can install a vapor barrier that reduces the amount of moisture that can make it into the wall, and we can make it easier for the moisture to get out of the wall, or evaporate to the exterior.

Unfortunately aluminum is not real good at letting moisture out, so unless you want to replace the siding, we should look at the other options. Reducing moisture is usually the easiest task. If you have condensation forming on many of your windows, the moisture levels are probably too high. We have addressed excess moisture in previous articles, but look for blocked or ineffective kitchen, bath or dryer vents, overuse of humidifiers, damp basements or crawlspaces, blocked gas appliance vents, etc. Install a permanent dehumidifier, if necessary. It also may be possible to reduce the moisture transfer into the walls by using a low-permeability paint on the interior surfaces. This paint acts as a partial vapor barrier. And make sure that your interior finishes are well sealed. Replaster any holes, caulk and seal cracks or gaps, and install foam gaskets at switch and receptacle boxes.

The seriousness of the problem depends on how chronic the moisture is. Occasional wetting is not a major problem. You don’t say if the wet material was decayed. If not, we suggest taking the measures recommended above and then monitoring the situation in the colder months. Look for moisture or stains coming from behind the siding during winter. If the wet material that you found is moldy or decayed, call in the professionals for a more thorough investigation.

I am shopping for a home and have heard that EIFS type stucco finishes are a serious problem. How do I know if the stucco exterior I’m looking at is this type?

EIFS or Exterior Insulated Finish System can indeed be problematic. It has been involved in class action law suits due to numerous cases of severe moisture damage to the exterior wall framing and sheathing behind this product. In essence, the EIFS stucco finish is applied over a rigid foam board applied to the exterior of the house. It is a very versatile and handsome finish that lends itself to very expensive looking architectural detailing and is becoming increasingly popular.

The problem is that water that enters at openings such as windows, doors, roof terminations, and other such details, due to poor flashings or seals, and then becomes trapped behind the finish, causing chronic soaking of the wood framing and sheathing. Water may enter behind other sidings such as vinyl in the same manner, but typically drains out, thus reducing the incidence of decay. The manufacturers have responded by demanding better attention to flashing details around openings, and in most cases by recommending the installation of an open weave type drainage mat behind the foam board.

To answer your question though, first be aware that very few homes in this area have been built with this product (although you can see many new commercial buildings receiving this finish). Any homes with this finish are likely to be relatively “high end”, (EIFS is not inexpensive), and the house must have been built relatively recently. If your home doesn’t fall in this category, don’t worry.

If the house is recent, identification shouldn’t be too difficult.

Since the relatively thin layer of stucco is applied directly over foam, the finish is quite susceptible to minor impact, so dents, scrapes or cuts may be noticeable. A light rap with the knuckles should be enough to detect the slight “give” associated with a product adhered to foam.

You needn’t avoid a house with an EIFS finish, but it should be thoroughly and professionally inspected, and well maintained, if serious problems are to be avoided.

The vinyl siding on my house has a wavy or puckered appearance, especially when the sun shines from an angle along the side of the house. Can this be repaired or does the siding have to be replaced?

The effect that you are seeing is very common and is generally due to overly tight nailing of the siding to the house, and is usually associated with a cheaper grade of vinyl. Vinyl siding expands and contracts significantly with changes in temperature. Vinyl siding is designed with nailing slots rather than simple holes at the top of each piece of siding to allow for this movement. If the nails are set too tight, the vinyl can’t slide back and forth at the nails, resulting in buckling of the siding in a tight pattern that results in the puckered appearance. The siding should be loosely hung from the nails, rather than being secured to the house. The siding must also be cut short to allow for expansion, especially if installed during cold weather. If the vinyl is cut too long, the sections that don’t have room to expand will buckle, even if the nails are sufficiently loose. Heavier gauge vinyl siding is much less vulnerable to this wavy appearance, commonly referred to as “oil canning” but proper installation remains important for good appearance. Vinyl siding is also susceptible to excessive heat that can result in permanent distortion of the affected surface. This is usually caused by gas grills being set too close to the siding during operation, but can also be caused by sunlight reflecting off an adjacent window. The other process that can result in a poor vinyl appearance is staining that occurs at nail locations. A chemical reaction that occurs with the metal of some nails can cause a discoloration that penetrates through the vinyl. This can sometimes be quite pronounced. None of the deficiencies that have been included here can normally be corrected without complete replacement of the affected portions of the vinyl siding. It is generally easy to remove and replace portions of the vinyl siding, but getting a good color match for any older siding is virtually impossible.

My house has aluminum siding on the original part and vinyl siding on the addition. I would like to paint the siding all one color. Can I do this and what should I use?

Aluminum siding can be very easily painted, and if well prepared will usually hold the paint longer than wood siding. Vinyl siding is a little more problematic, but can be successfully painted. We have seen several homes with painted vinyl siding that look good after five to ten years of exposure. In either case, using high quality materials and taking the time to prepare the surfaces properly should ensure satisfactory results. Preparation involves washing the siding to remove dust, mildew or algae, and any residue of chalking paint. A power washer can be used, but hand washing with a detergent and water will work. Be careful using a power washer to prevent damage to the siding or trim, and to avoid leakage into the house. Be sure to rinse well so any soap residue will be removed, and then allow a few days for thorough drying. Because vinyl siding expands and contracts significantly, you should use a high quality exterior grade acrylic latex paint, which can stretch with the siding and has very good adhesive qualities. One word of warning; it is very important that you paint vinyl with the same or a lighter color than the original vinyl color. Darker colors will increase the temperature of the vinyl at the hottest times of year, resulting in permanent buckling or distortion. Anyone who has left the gas grill a little too close to the siding can attest to its sensitivity to heat. Some authorities recommend adding special bonding agents to the paint when applying to vinyl. It may also be helpful to use a high quality latex primer, since the adhesive qualities of primers are usually superior to finish paints. It will probably also be wise to add a mildewcide to the paint. Using an airless sprayer to apply the paint should result in a more even and professional looking finish, but is not absolutely necessary.

I have masonite siding on my house, built in 1965. The siding is deteriorating, especially along the bottom. What’s the best way to repair this siding?

You are probably describing a pre-primed wood product, commonly called hardboard siding. It essentially consists of pressed and glued sawdust, formed into ½ inch thick by 11 inch wide boards that usually come in 12 foot lengths. The siding is typically installed horizontally on the house, with each course lapping the course below, leaving 10 inches of exposed board. This material is quite vulnerable to moisture and must be kept well sealed and reasonably protected in order to provide long life. Allegations of premature failures of this product have resulted in a class action lawsuit against one manufacturer, Louisiana Pacific. In your case however, the deterioration can hardly be considered premature. The typical life for the product is approximately 30 years, so you have done well to get this far. Any repairs such as patching, filling, and sealing will not be very effective with this material. Once the swelling and deterioration begins it is pretty much impossible to stop. You should be able to buy new hardboard siding to replace the deteriorating sections, as long as the affected areas aren’t too large.

Preventive maintenance is the key to long term success with this siding, or any other exterior finishes for that matter. Splash damage is the most likely culprit causing damage to your siding, although poor flashing details at decks, close proximity or contact with soil, and any other conditions that result in excess moisture can contribute to the decay. Correction of any of these conditions should be addressed before replacing the damaged materials. Splash damage is usually due to missing or poorly maintained gutters, or missing overhangs. Keeping gutters clean and free of leaks, and monitoring for bypass, (water sneaking behind the gutters), should be easy to handle. Missing overhangs can be a bit more difficult to correct. Many houses built in the 1940s though 1970s did not have good roof overhangs on the gable ends, and some houses weren’t built with good overhangs at the eaves either. Overhangs can be added to most houses of any age. This is most cost effectively done when the house is due for a roof tear-off and replacement. We recommend that overhangs be installed on any house that doesn’t already have them.