Deicing Wood Decks

Deicing Wood Decks

After we completed building our 1500 sq foot Alaskan yellow cedar and western red cedar deck I knew I’d have to do a bit or research to find a deicer that would not harm the deck, or the house. Here is what I found.

In cold climates deicing of wood decks is often a necessity if the deck is going to be used safely. Selecting the wrong deicer can significantly reduce the life of the wood and fasteners in the deck. The most readily available and lest expensive deicer sodium chloride (salt) should never be used because salt is by far the most corrosive of all the deicers. Salt will be absorbed into the grain of the wood and will slow precipitate back out every time the deck is wet greatly reducing the life of the metal fasteners. Salt also attracts and holds moisture.

Deicers that contain potassium chloride are not as corrosive as sodium chloride, but they too should not be used on wood decks because they are still way too corrosive for metal fasteners.

Urea based deicers also known as ammonia sulfates are considered fairly safe around pets, children and are not very corrosive to fasteners. However, urea based deicers should be used carefully if your deck is located near streams or lakes because urea which is also used as a fertilizer releases nitrates. Increased levels of nitrates in some water bodies has increased the growth of both native and invasive species of aquatic plants to the point that the water losses oxygen and kills fish. So, urea based deicers should only be used in areas where water runoff will not enter streams and lakes. In some areas ammonia sulfates are banned so if you are going to use them be sure to check with local regulations.

Of all the various deicers it is clear to me the most environmentally friendly as well as the least corrosive is Calcium Magnesium Acetate (CMA). In fact some studies show that CMA is also a wood preservative because the calcium neutralizes acids and it inhibits rust and other metal corrosion by neutralizing salt’s natural corrosive properties. (If you live near the cost airborne salts will be partially neutralized by CMA) The biggest drawback to CMA deicers is that they are several times more expensive than other deicers. However, if you look at the cost of deck maintenance and replacement then CMA deicers are a real bargain. Luckily CMA deicers are becoming less and less expensive as municipalities and other large users of deicers are purchasing larger quantities each year. They are doing this because they are finding that using CMA deicers cuts maintenance cost on roads, bridges, and other structures.

Before I totally decided to use CMA as the deicer on my deck I had a few more questions to answer. Here they are:

1. How is Calcium Magnesium Acetate made? CMA is a combination of dolomitic lime (limestone), magnesium and acetic acid the same acid that is found in vinegar.

2. Is CMA safe around children and pets? In many tests CMA has proven to be as safe as common table salt to children and pets.

3. What temperatures does CMA work in? CMA works best above 15 degrees Fahrenheit but will work down to temperatures of -20 degrees or lower. (Check the manufactures label and recommendations.)

4. What is the environmental concern when using CMA? CMA like all deicers does have some concerns. It has been shown to deplete oxygen in water, but far less than urea based deicers. In many test CMA has shown to be the least harmful of all deicers to water quality.

5. What does CMA do to floors and carpets? Like most deicers CMA is water soluble so it will clean up easily and does not harm most floor surfaces.

6. Does CMA harm vegetation? CMA of all the deicers is one of the least harmful to most vegetation.

There is one last thing to consider with all deicers when used on decks. Make sure you check that the deicer you select doesn’t include dyes that could discolor the wood. I ran out of CMA deicer and substituted a deicer with potassium chloride that contained a green dye; now I have some permanently green stained wood in portions of my deck. Of course read and follow all the instructions on the packaging.