A paver patio, walkway or retaining wall is built to last decades, but a New Hampshire winter is the hardest test it will ever face. The damage rarely comes from one big storm. It comes from water sneaking into joints and soil, freezing, thawing and freezing again, with deicing salt making the cycle worse. Here’s what actually helps, based on guidance from the Concrete Masonry & Hardscapes Association (CMHA, formerly ICPI), UNH Extension and NHDES.
Why Concord winters are hard on hardscapes
Freeze-thaw is the real enemy. Using NOAA daily records for Concord Municipal Airport from 1991 to 2020, we counted the days where the high climbed above 32°F and the low dropped below it. Concord averaged about 110 of those days a year, with the busiest stretch running November through March (roughly 18 in November, 17 in December, 13 in January, 16 in February and 21 in March).
Every one of those days is a chance for meltwater to soak into a joint, a crack or the soil behind a wall, then expand as it refreezes. Pavers themselves are tough. Concrete pavers made to the ASTM C936 standard need at least 8,000 psi compressive strength and no more than 5% water absorption, and they’re tested for freeze-thaw and deicing salt durability. The weak points are usually the joint sand, the base and drainage, and how the surface is treated all winter.
Before the first storm: get the basics right
- Fix lifted pavers now. CMHA recommends repairing heaved or lifted units with more than 1/8 inch of lippage before winter, because plow blades and snow blowers catch raised edges and chip them.
- Top up joint sand. Joints that have washed out let more water and salt into the bedding layer. Refilling them (or using a polymeric or stabilized joint sand) helps keep water out.
- Check drainage. CMHA recommends paver surfaces slope at least 2% so water and deicer run off instead of pooling. Puddles in October become ice sheets in January.
- Clear wall drains and weep holes. A retaining wall needs water to get out from behind it. If the gravel drainage zone or outlets are clogged, saturated soil freezes and pushes on the wall. Leaves and mulch packed against outlets are a common culprit.
- Consider sealing. A sealer isn’t required, but CMHA notes it can further cut down on water entering joint sand.
If a wall is already leaning, bulging or has blocks shifting, have it looked at before the ground freezes. Our retaining wall team can tell you whether it’s a drainage fix or a rebuild.
During winter: snow removal that doesn’t hurt your pavers
- Shovel or plow first, salt second. CMHA’s guidance is to remove snow mechanically and save deicers for ice from freezing rain or refrozen melt, not to melt whole snowfalls.
- Plow on a diagonal. Working diagonally to the joints makes it less likely a blade catches a paver edge. Plows and blowers with skid shoes that keep the blade slightly above the surface help too.
- Use plastic or rubber-edged shovels on patios and walkways, and don’t chip ice off with a metal edge.
- Clean up slush and leftover salt. Once it’s loosened, push it off the surface so salt doesn’t concentrate in the joints.
Picking the right deicer for pavers
Not all ice melts are equal on concrete. The CMHA’s position on concrete pavers is:
- Rock salt (sodium chloride) is the least damaging to concrete and should be the default.
- Calcium chloride is fine used sparingly when you need faster melting in colder weather.
- Avoid magnesium chloride and CMA (calcium magnesium acetate) on concrete pavers, because the magnesium can chemically degrade concrete.
- Follow the label dose. More salt doesn’t mean more safety, just more damage and runoff.
Keep in mind that rock salt slows way down in deep cold. NHDES notes salt is largely ineffective below about 15°F, so on those mornings, sand or grit for traction is the better tool. (On permeable pavers, CMHA recommends jointing aggregate instead of sand so the joints don’t clog.)
Don’t forget the plants next to your hardscape
Salt that washes off a patio or walkway ends up in the beds beside it. UNH Extension warns that salt spray browns evergreen needles and that salt in the soil keeps roots from taking up water, which stunts plants. NHDES adds that salt scatter can kill landscaping and that New Hampshire already has more than 50 waterbodies impaired by chloride.
A few simple habits help:
- Aim salt at the walking surface, not the edges of beds.
- Don’t pile salty snow on shrubs, perennial beds or the top of a retaining wall.
- Wrap salt-sensitive evergreens near driveways in burlap.
- Water beds deeply in spring to flush salt out of well-drained soil.
If a bed took a beating, our landscaping services crew can replace damaged plants with tougher choices in spring.
In spring: inspect and repair early
When the snow is gone, walk your hardscape. Look for sunken or lifted pavers, empty joints, white efflorescence or flaking, and any change in how a wall lines up. Small settling is usually a quick reset; ignoring it lets water in for another season. Spring is also the time to rinse leftover salt off surfaces and out of beds.
Need help this winter?
Globe Green builds and repairs paver patios and walkways and retaining walls across the Concord area, and our snow removal crews plow commercial lots and HOAs in the region plus residential driveways in Concord. Call (603) 420-7771 to set up a fall walk-through or get on the plow list.
FAQ
Will rock salt damage my paver patio?
Rock salt (sodium chloride) is the least damaging deicer for concrete pavers, according to the Concrete Masonry & Hardscapes Association. Use only the label amount and clear away slush and leftover salt so it doesn’t build up in the joints.
What ice melt should I avoid on pavers?
Avoid magnesium chloride and calcium magnesium acetate (CMA) on concrete pavers, because the magnesium can chemically break down concrete. Calcium chloride is acceptable when used sparingly.
Can you plow a paver driveway?
Yes. Pavers can be plowed like other pavement, but plowing diagonally to the joints and using skid shoes to keep the blade slightly raised reduces chipped edges. Fix lifted pavers before winter so the blade doesn’t catch them.
Why do retaining walls lean or bulge after winter?
It’s usually water trapped behind the wall that freezes and pushes on it. Keeping the wall’s gravel drainage and outlets clear helps, and a wall that’s already moving should be checked by a pro.
How many freeze-thaw cycles does Concord, NH get?
From 1991 to 2020, Concord averaged about 110 days a year where the temperature crossed 32°F, based on NOAA daily records for Concord Municipal Airport. Most of them fall between November and March.
Should I seal my pavers before winter?
Sealing isn’t required, but it can reduce how much water gets into the joint sand. Refilling worn joints and making sure the surface drains matter more.