# Building Berms



## wppjeff (Sep 23, 2009)

I've helped build a few berms in the past, but I'm looking for some solid do's and don't on berm building. Has anyone seem any good threads or articles about this? Or have any personal experience info? Thanks!


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## dburatti (Feb 14, 2004)

Since no one has responded yet...

First, use good dirt...a mixture of clay and loam. You want it to pack but not crack when it dries.

If you can help it, don't put the berm where it'll hold water. Try to allow any water caught by the berm to flow out one end. If your berm catches water, build up the ground a little next to the berm to push the puddle away from it so bikes won't ride through it if they're on the bottom edge of the berm.

The shape should consist of a constant radius. You don't want it to kink, or tighten, as it progresses. If the radius opens a bit toward the end, that's acceptable in situations if it aid the flow of the trail.

Depending on speed, you probably won't need a three foot high berm. Start with one 12" to 18" high, ride it to check flow, and add more dirt as needed.

If you don't have a lot of dirt, you can rake your organic material to help fill in under the berm. You can also use rocks & logs, though be aware of deterioration affecting the berm after a while.

Cupping: You probably don't want the face of the berm to be flat. You'll want it cupped a bit, and cupping shape depends on speed of riders and height of the berm. 

That should be a good start.

D


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## wppjeff (Sep 23, 2009)

Thanks for the help. There isn't much dirt, so I was going to wheel in some sand bags. I'm not sure if that would be legit because of the bags, but they seem to be biodegradable enough to not cause any problems. Thanks again! :thumbsup:


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## tflounder (May 12, 2008)

We have sandy conditions here as well. The main thing is to establish a firm base that will not shift. Sandbags will work - we use gravel/rocks as a base and then apply a thin coat of sandy soil. The gravel is shaped into the curve so that the berm ends up in the middle of the trail. The sand is applied to hold the gravel in place and to establish a smooth ride. During dry periods the sand may loosen and collect at the bottom of the berm - simple raking can remove any excess sand that collects.


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## perttime (Aug 26, 2005)

I am not really into building trails... more like directing things in a way that allows a trail to form... so, if the ground is not totally flat, you could probably find some existing ground features to exaggerate, instead of randomly deciding you want a berm "here", and building it all up.


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## hankthespacecowboy (Jun 10, 2004)

You'll never build a berm too big...


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## bitflogger (Jan 12, 2004)

hankthespacecowboy said:


> You'll never build a berm too big...


I've seen time and energy wasted on berms to nowhere or that don't work. Also more berm than is needed or not enough in the right places.

I suggest having an approximate line cut and ridden in some cases and then one will know best where to build and how much.

I have also seen a lack of consideration for drainage where having an approximate line and watching what happens with rain ahead of time helps.

Measurement tools also help. I have locked horns with volunteers and professionals over this and time proved me right to use tape measure, clinometer, stakes and flags.

Yeah, I can spoil the fun but I've been doing trail building, watershed remediation and landscaping longer than a lot of my trail helpers have been alive and I'm also in a position where I report to and hear from land owners and the public.


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## Irishbuddha (Feb 25, 2004)

bitflogger said:


> Measurement tools also help. I have locked horns with volunteers and professionals over this and time proved me right to use tape measure, clinometer, stakes and flags.


Can you provide a little more info on measurements? Is there some rule of thumb for speed and radius? What tools are you using to establish the radius? Any quick and dirty tricks?

Thanks!


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## cmc4130 (Jan 30, 2008)

i spent 20+ years riding bmx (and skateboarding) before switching to mtb 4 years ago. i LOVE berms. i dream about berms. berms are both science (physics) and art.

in general, you need a big radius to soak up high speed. look at Downhill runs and BMX tracks. for slow speed and a berm you want to "whip" out of (like backyard pump track) you want a tight radius.

maybe you should take some pics of the spot you are looking at and describe the gradients etc....

*bikemojo thread: "nice berm"*
http://www.bikemojo.com/speak/showthread.php?75951-nice-berm

*Ridemonkey.com > Biking Forums > BMX & Dirt Jumping > Berm styles.... Ribboned / Banked / Bowl-cornered / RAY'S style...* 
http://www.ridemonkey.com/forums/showthread.php?t=216752

*Ridemonkey.com > Biking Forums > BMX & Dirt Jumping > 270 berm thread.... post up*
http://www.ridemonkey.com/forums/showthread.php?t=214931

*Ridemonkey.com > Biking Forums > BMX & Dirt Jumping > pump tracks *http://www.ridemonkey.com/forums/showthread.php?t=217062


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## bitflogger (Jan 12, 2004)

Irishbuddha said:


> Can you provide a little more info on measurements? Is there some rule of thumb for speed and radius? What tools are you using to establish the radius? Any quick and dirty tricks?
> 
> Thanks!


I spoke about slope, fall line and drainage as much as or more than anything. I use a tape measure, clinometer and I'll wrap bright flag at same distance from each other around a pair of stakes of same length. I also use pin flags and marking paint.

I don't have any firm answers regarding radius and that's why I prefer to have the corridor or general line done first. I learned that one after seeing people make what I'd describe as berms to nowhere and have to work out making them functional later.

My not being so quick to just start digging spoils the fun for some but I'm in the circle who reports to land managers and the non-riding public and prods to get things done.


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## cmc4130 (Jan 30, 2008)

*Bermed corner photos?* 
http://forums.mtbr.com/showthread.php?t=381772


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## dburatti (Feb 14, 2004)

If you're corridor is relatively clear and the ground free of trip hazards, you can approximate the speed you'll have and the arc you'll need by running that piece of trail. Just remember to put your hands on your invisible handle bars and make a sound like a motorcycle.

Seriously, running trail to check flow does work well in a lot of cases.

D


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