Feb 1, 2011

Protecting Brick Pavers and Steps from Winter damage

Options for protecting your paving stones and steps from de-icing materials

I was recently contacted by a civil engineer in eastern Pennsylvania about solutions to protect interlocking pavers and modular retaining wall blocks & caps from the ill effect of de-icing materilas during the winter months. Below is his email and my response for helping his clients protect their investment in high density concrete pavers & blocks.

Civil Engineer:
I enjoyed finding and reading your blog today.  I am a civil engineer in eastern PA and so I spec a lot of modular retaining walls, but have never seen a contractor provide the detail and information that you do for post-installation maintenance.
I did have one question that i would like to pick your brain about, if you have the time.  Quite a few of the people who install these also salt the modular retaining wall steps over the winter and I've seen them crack, chip and deteriorate even sometimes after just one or 2 winters.  Is this normal and should I warn them about salting the stairs?  Because it seems that affects the block more than the temperature variation.
My Response:
Good to hear from you.  I am assuming you are referring to commercial or municipal applications which use alot of rock salt during the winter.  There are a few things that I believe will help this problem. Modular retaining walls & caps are denser than poured concrete so there absorption rates are less.  Assuming you are specifying a quality product, it should considerably outlast poured concrete but corrosive materials will still break down their structural integrity or surface.

The first and easiest step would be for them to reduce the amount of rock salt used. I know liability is a factor but excessive use of rock salt will break down any concrete product. Also, the use of liquid de-icers are showing better results too.

The second option is for them to use a calcium chloride based product or similar "ice" melt (white pellets), NOT rock salt.  I know this is not usually reasonable with municipalities. Residential applications can easily switch to this option. This option is more expensive but preserves the life of the concrete products and is better for the surrounding landscaping.

Another option would be to seal the high density concrete pavers, walls, & caps with a water base paver sealant.  This is a tricky situation in commercial or municipality applications.  The reason is that the areas need to be cut off from access for prep cleaning, sealant application, and curing.  If you do in sections, the result of  the sealer may show some noticeable differences due to weather & temperature conditions during appliapplicationo, the sealer will initially be slick which can create some liability issues if wet. This sealant will wear in over a few weeks.  Residential applications can easily be controlled. 

One last option that comes with an initial large cost but is greatly recouped over the years is the use of heating coils. There are several options of heating the paving stones & modular retaining wall system and I can not claim on being an expert on their use but only on their results.  When you consider the cost savings of salt application (labor & product) and long-term replacement cost versus the added electric bill (or natural gas) and initial installation cost, melting snow & ice with an effective heating system makes financial sense.

The Step treads should be modular retaining wall cap units that are adhered to the wall blocks that create the rise.  These caps units can be pre-sealed weeks before installing them since they do not require any compaction. These cap units take the brunt of traffic and weathering.  Modular retaining wall & cap units do not have the same density as the paving stones.  The faces of the wall units used for step rises can also be pre-sealed if the project is not too large. Pre-sealing paving stones is not feasible.  Pre-sealing will add to the installation cost and needs to be included in the initial bidding specifications. Keep in mind that good paver sealants in normal conditions only last 2-3 years and will need future application.

I also need to stress the use of a quality product.  High density & low absorption rates are critical.  Unilock, Inc is one of the best throughout the Midwest and your area. They have plants in New York and I am sure they are distributing in your area. There are many other good paver & wall block manufacturers and if you are considering one, check there independent test results for density (psi) and absorption rates. Cover yourself in the initial specifications by specifying minimum rates.

The damaging effects of Winter, frost heaving & de-icing materials, are one of the main reasons interlocking pavers and modular retaining wall systems were created. But the biggest threat to the structural integrity of concrete products are de-icing materials.  De-icing materials, especially rock salt, can penetrate the concrete products and begin to etch & deteriorate the surface, therefore speeding up the ill effects of weathering. The options above will help you avoid future repair & replacement costs from the effects of Winter.