6 Tips to Assess Wet Rock Before Climbing

Climbing Wet Sandstone Damages the Rock and Routes

Men bouldering at night with a headlamp on.
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Before you go rock climbing after it rains, you need to ask yourself a bunch of questions to determine if the rock is dry so that you won't damage or destroy routes and boulder problems.

Here are three questions to ask before climbing:

  • When can you go climbing if it has been raining or snow is melting off a cliff and the rock is saturated with water?
  • How should you assess the rock surface of sandstone formations to determine if climbing will damage the surface and degrade or destroy routes and boulder problems?
  • What are the factors that affect the drying of sandstone?

Climb Granite and Metamorphic Rock after Rain

Some types of rock, like granite and most metamorphic rocks, dry quickly after precipitation so it is easy to assess the rock surface and determine if climbing will damage it. These rocks are hard, erosion-resistant, and generally impermeable to water so rain runs off and the surface dries relatively fast, even on cloudy days. After it rains, it is always a good choice to go climbing on granite cliffs.

Porous Sedimentary Rocks Remain Wet after Rain

Sedimentary rocks, however, are porous and absorb water, leaving the rock surface and even the subsurface wet after heavy rains. It's a judgment call as to when to climb and how deep the moisture has permeated the rock surface. A quick but heavy thunderstorm will usually just wet the outer surface layer of sandstone since most of the water runs off the rock. In the case of an afternoon thunderstorm at Garden of the Gods in Colorado Springs, the east-facing cliffs are usually climbable the following day after baking in the sun through the morning. After prolonged rains, however, the rock surface will be wet below the surface, sometimes as much as two or three inches, so it is important to let sandstone dry completely before climbing on it.

Sandstone Loses Lots of Strength when Wet

Sandstone and other sedimentary rocks like conglomerate soak up moisture like rain and snowmelt like a sponge. The water, soaking the rock surface, dissolves cementing agents like clay, silica, and salt between sand grains, allowing the sandstone to lose as much as 75% of its dry strength. Another by-product of wet rock is sand. As the cementing agents dissolve, the individual sand grains are released from the rock matrix. That's why the surface of sandstone cliffs accumulates sand on handholds and footholds after the rock dries.

6 Guidelines to Assess Wet Rock before Climbing

If you climb on wet sandstone, you will easily damage the rock surface by breaking off flakes and edges, sometimes completely changing the character and grade of a climbing route or boulder problem. Follow these guidelines to assess wet rock and decide when you can climb without damaging the sandstone:

  • Assess the cliff and your proposed route by looking for moisture and wet rock. Look at the cliff base and staging area. Look for dark damp areas on the cliff face. Look at flakes and see if moisture is behind them. Look for fresh sand liberated from the sandstone on ledges and holds.
  • Consider the cliff area where you want to climb. What is its location? Does it get lots of sunshine that will dry the rock? Is it in the shade so the rock will stay damp for days? Are trees shading the route and keeping it from completely drying? Does a groove carry water down the cliff onto the route?
  • Wait at least 24 hours after rain before climbing. This usually applies to thunderstorms that drop quick heavy rain on a rock that is already hot and dry as in summer. Much of the rainwater usually runs off and soaks into the rock at the cliff base or on ledges and shelves. Most cliffs dry in 36 hours with plenty of sunlight. In winter you may need to wait three or four days for the rock to completely dry.
  • If the ground and rock at the base of a cliff or route are wet the day after a storm, then there is probably subsurface moisture and you shouldn't climb. Ditto if the trail to the cliff is wet and muddy.
  • Don't climb a route if any part of it, including the base, is still wet. If you do, you risk breaking off key handholds, damaging footholds, and wearing grooves with your rope in the sandstone. Also, remember that cams can fail in wet cracks so if you are jamming at Indian Creek, then make sure the inside of the crack is dry before placing cams.
  • Consider the weather conditions. Sandstone dries quickly on hot sunny days as well as on windy days. It will dry slowly if there is high humidity, overcast sky, little direct sunlight, and little or no wind. Remember that snow, which melts slowly off ledges, wets the rock and then freezes at night creating a soaked rock that is very susceptible to damage when climbed.

Read more about wet rock at When Can You Climb on Wet Rock?