Olympic detox: best practice for bouldering on sandstone in Font, 70km south of Paris

Font is home to myriad giant, sandstone boulders, in all sorts of tempting shapes inviting you to grab them with both hands, and feet. But as a soft, porous, sedimentary rock, we need to avoid climbing on it when it’s wet because you can slip off and/or erode the holds very easily. Sandstone does have a harder, outer crust which we want to keep in place to protect the even softer rock underneath, so there’s a code of best practice to follow.

The advice for climbing on the Font sandstone boulders is the same as that for the Southern Sandstone in the UK. Help us to protect this fragile rock and preserve it for many more years of enjoyable climbing. Here are our essential tips for bouldering on sandstone:

Sandstone bouldering best practice

1 Only climb when the rock is completely dry, this could take 24 hours or more, but the waiting time depends on the amount of rain and how much sun reaches the boulder to dry it out. Different areas of the rock may dry quicker than others, but sandstone is weakened when damp, so be patient.

1 Use a large bouldering mat to reduce erosion on the ground below the rock, and to protect yourself when you fall.

2 Clean your shoes before you do a new project or route. This not only stops you from slipping but minimises any sandpapering effect of the loose sand rubbing on the holds.

3 Only brush holds lightly with a very soft dustpan brush not a toothbrush or regular bouldering brush as these are too harsh for sandstone and will damage it.

4 Leave any vegetation on the rock like plants or moss in place, these are important for biodiversity and wildlife and need to be respected. Some sandstone sites are conservation Sites of Special Scientific Interest (SSSI) with the flora and fauna there protected by law.

5 Use as little chalk as possible, not only is this cheaper for you, but it saves the rock. Too much chalk builds up and impregnates the sandstone, encouraging future climbers to clean the holds more vigorously which over time will erode them away, making the boulder problem first harder and then unclimbable.

6 Avoid placing tick marks in chalk to highlight holds for the same reason as above, the less chalk used on sandstone the better. It also spoils working out the route for future climbers if they can see exactly where all the holds are immediately.

7 No chipping ever - chipping means hammering and chiseling new or deeper holds into the natural rock. We like to think this one is obvious as it goes against the challenge of bouldering and climbing!

We need your help

If you see people not observing this best practice, if you feel it is safe to do so, please approach them in a friendly way to explain how best to protect the rock, without aggression or talking down to them - they may be newcomers to climbing or outdoor climbing, unaware of these guidelines. Share this information here with them by showing this page on your phone too.

For more information on sandstone bouldering and climbing click here.

Extra tips for top roping on sandstone, outside of Font

1 Use a thick, static rope with about 3% stretch rather than the usual dynamic stretch climbing rope with 10-15% stretch on it. This avoids a cheese-wire effect on the soft rock which creates rope grooves.

2 Consider using a square or rectangle of old carpet to protect the rock from the rope from eroding a groove over the edge of the top of the rock, near the top rope clip.

3 No dogging! It’s not what you’re thinking - in climbing dogging refers to the belayer holding a fallen climber at the same height while they attempt and fail a hard move over and over again. This erodes sandstone so it’s not acceptable on this type of rock.

4 Once you’ve completed the route, top out (climb right over to stand on top of the crag). Then gather in the ropes from the top of the crag and throw them carefully back down, rather than abseiling back down. This avoids cheese-wire effect wear to the rock from your full weight on the rope. Instead, walk back down using a descent route.

Yikes! It broke!

Holds do break unexpectedly even if you have followed all this advice, and (in England and Wales) the BMC is can perform a repair on these areas to protect the softer sandstone underneath. Please contact your local BMC Area Rep with the location of the broken hold and exposed area so we can get our team of skilled volunteers to restore a synthetic, harder outer layer using materials like cement, shellac furniture polish (resin), PVA glue and wood hardener.