Ask The Experts

• I have a terrible problem with mildew and I don't seem to really understand what it is and what I have to do to get rid of it. Will you please help?
  


• We have recently had tile installed on the floor in our entryway and guest bath in our house. The problem is the grout is cracking and coming out of the joints. What could cause this?
  


• We have an electric range right now and want to change to gas. Our hood does not have any pipe going through the roof, and the salesperson said we should have one for proper venting. Is this true?
  

 

-Mark from San Ramon

A:Mildew is one of the most common and persistent causes of house paint failure.

Mildew is the visible result of a type of fungus growth... a mold that grows on the surface of organic and inorganic matter. It frequently attacks exterior painted surfaces, particularly those situated in warm, humid or shady locations. It appears as tiny spots of brown, black or purple discoloration resulting in a dirty, unattractive appearance which becomes progressively worse due to the entrapment of dirt in the mold web.

Mildew grows on many types of surfaces. Like any living organism, the mildew fungus requires food. It flourishes on the nutrients found on the top of the house paint (such as dirt), and on the wood beneath the paint film. It quite often grows completely through the paint film, much like the roots of a tree, bringing about a complete deterioration of the paint. Paint manufacturers have tried to solve the mildew problem by developing paints with the most mildew resistant materials. Unfortunately, any good mildew resistant paint film is only as good as surface preparation prior to painting.If mildew is definitely present on the surface to be painted,it is absolutely necessary to do a thorough job of cleaning and removing this existing mildew before painting is started. One of the best products to use is manufactured by Pittsburgh Paints and is called "Mildew Check", a patented mildew cleaner.

Since mildew will sometimes appear visually as a dirt collection, it is wise to test a surface for the presence of this fungus before painting. A very simple test can be conducted to determine if the mildew is present. This test consists of placing a few drops of common household bleach on the suspected surface and observing the result. If the drops of bleach cause the surface to lose its blackish or brownish appearance,the there is reason to believe that mildew is growing on the surface.

 

-Kathy from San Ramon

A good cleaning will result in a more satisfactory and longer-lasting paint job. For cleaning painted exterior surfaces containing mold, mildew, algae and dirt, another Pittsburg Paint Mildew Check Mildewcidal/Algicidal Multi-purpose Wash is suggested.

This product is a unique house wash that is designed to remove and kill mildew and algae. Unlike conventional house washes or mildew cleaning solutions that simply clean the surface, Mildew Check Multipurpose Wash leaves behind a protective barrier which resists mildew and algae growth. Mildew Check Multipurpose Wash must be mixed with household bleach. Before use, be aware that this mixture presents hazards to the applicator and surroundings.Be sure to read and follow the directions for mixing and application. After using this product wait 24-48 hours before applying paint.

 

-Sara, Danville

A:That salesperson was correct. If you have a hood that does not penetrate the roof or walls, then you have what we call a ductless hood. You see a lot of these used in electric range installations. They use a charcoal filter to filter out cooking odors and re-circulate the air back to the house.

Your new gas stove hood should be a minimum of 500 cfm, and must be ducted to the outside of the house.You see, when you burn gas it gives off carbon monoxide,and you want to insure that all the fumes are removed from the area for your own safety.

Also, you want to make sure you will be able to get gas to the location in sufficient volume to allow all your gas appliances to burn efficiently. You just cannot assume that you can tap your gas line into another gas appliance such as the water heater or the furnace. You should have your system checked by a qualified individual for the proper size piping to run your gas system. You may have to run the line clear back to the meter. Gas operates a very low pressure, so it must have volume.

If you like to cook, gas is the best way to go. You have much more control over the heat, and your food will be enjoyed as never before.

 

A:No definitive answer can be given without inspecting the jobsite and looking at your existing construction details. However, I will try to give you a few signs to look for.

• Could be a combination of bad grout, bad mixing additives such as the water that was added or an old latex additive that has expired beyond its shelf life.
• A substandard installation could be poor penetration of the grout into the grout spacing, including the possibility of using the sanded verses non-sanded grout, depending on the application.
• Poor underlayment preparation and adhesion causing movement in the underlayment is another possibility to check. Try to determine whether a cementious board such as Durock or Hardibacker was used or was the floor floated with mortar. In any case where they secured properly?
• Lastly, check the construction of your sub flooring, many homes built in that era used 5/8" sub floor in original construction and although this meets code it "gives"quite a bit and if tiling is to be done over these types of floors it should be floated with a mortar bed prior to tile installation. Otherwise the give in these floors will crack your grout and in the future may crack a few tiles.

Please keep us posted as to your findings so we may pass them along to our readers and thanks for your question.

Good luck and keep those questions coming in.
David Pinsley, CR, CGR, General Contractor