Every year I see more and more people removing three, four or five feet of snow from the bottom edge of the roofs on their homes. People need to know that, in a winter like this, if you do this you are going to have problems and may cause serious leaks into your house.

First let me share some basic information.

An unfinished attic should be as cold as the outside temperature. Homes built in the past 30 or 40 years have nice wide eves with vents and a ridge vent to keep the attic cold and prevent heat from reaching the roof. Some of the older homes, small capes and such, don’t have that venting and, though insulated, there is heat lost that reaches the roof.

When there is a foot or so of snow on the roof, the heat lost to the attic space will melt the snow next to the roof. Water will run down under the snow that is acting like insulation until it gets to the edge where the snow ends and then that water starts to freeze. That is what causes ice dams.

If the roof was done, say, in the past 15 or 20 years by a good roofer, he applied some ice and water shield on the bottom three to six feet of the roof under the shingles. That product seals around the nails and probably 98 percent of the time does not allow water to leak in. So ice on the bottom of a roof is no longer a problem.

Now, if you remove those three to six feet of snow along the lowest edge of the roof, when the water under the snow on the upper part of your roof runs down it will start to freeze where you removed the snow. So now you have an ice dam three to six feet up on your roof and there is no ice and water shield there to protect the roof.

The best rule to follow is the all-or-nothing rule: Remove all the snow, top to bottom, or none. And when I say “remove all,” don’t scrape down to the shingles. You can leave a few inches if possible and that will allow any melting to freeze and you won’t damage your shingles.

And always shovel down from the top, so you won’t get under the shingles, lift and tear them. I can tell you, trying to repair shingles during this time of year is not fun.

Just so you know, I have been roofing, both full-time and part-time, for 50 years.

So, just because you see your neighbor take those three feet of snow off his roof edge, please don’t do the same. And if you do have a leak from ice dams, remove the snow and the leaks should stop.

Moe Galarneau is a resident of Auburn.