# Building jumps with logs and dirt



## Blue Sugar (Feb 16, 2004)

We just got permission to build a jump line at our local park and I now have to figure out what to build them with. LM wants "natural materials"- in other words no processed lumber. we have plenty of downed trees and I'm thinking about laying logs down and covering them with dirt. I figure we could use different size logs to shape the jumps. I realize it's a method not without problems but it would be by far the most expedient way to go. Does anyone have experience doing this? Thoughts?


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## Taroroot (Nov 6, 2013)

In our neck of the woods, logs become termite and rot farms in short time. Last maybe a couple years or so.


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## Torgy (Mar 8, 2016)

Any large stones you could make use of instead of logs?


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## JustMtnB44 (Nov 8, 2004)

That method only works if the logs are extremely rot resistant wood. We don't have much of that here in Western PA where I am so we use as many large rocks as we can find and then dirt for the rest. If that means using a wheelbarrow to move material, we do that. The most expedient way is almost always the way that will have you repairing what you built in a few short years.


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## MX9799 (Feb 11, 2018)

It works OK. I've done it on my own private trail here at my house since i don't have a whole lot of dirt and/or rocks to work with, plenty of trees and logs, and any dirt I do get I have to hand dig.

It will pack down after some use, so be ready to throw some more dirt on it soon after the bikes start hitting it. In my experiences it seemed like the faces got steeper as the dirt packed into the underside face of the log. Once it's good to go though, it should stay solid until the log rots away. Just know from the get-go that in the future the jump will get a lot smaller when the log rots, and be ready to rebuild the jump when that happens. Mine have been going on two years using green cedar logs and they haven't started rotting yet. My jumps aren't huge jumps though. They're just small roller type jumps maybe 18" tall and the filler log was about 12" in diameter.


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## jeremy3220 (Jul 5, 2017)

Not an expert but ideally you'd use something like cedar and leave ends of the logs exposed so they can dry. If you just completely bury random deadfall expect it to rot very fast.


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## Sparticus (Dec 28, 1999)

I used to use logs years ago, don't do it anymore. Here in Oregon it's tempting inasmuch as we have lots of downed trees so plentiful organic building materials. But we also receive a lot of rain. There's nothing wrong with a log + dirt jump except for this: it won't last.
=sParty


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## Harold (Dec 23, 2003)

what I do on my backyard trail is not necessarily going to be the same as what I do on public trails.

backyard trail - sure, I'd use logs as fill. but I'd stick with something rot resistant (in my area, it's mostly black locust that's the rot resistant wood of choice).

public trail - nope. I'd do the harder work and obtain more dirt or rock to make my jumps more solid.


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## TimWebber (Jan 29, 2016)

I dont use logs as "fill" because they will rot and the jumo will slump. I do use logs as a "frame" to support the dirt for jumps. In this area its mostl white spruce whixh is fine for five plus years if its not started to rot. When the frame material does fall away, the edges of the jump start to wear. No biggy tho, make another frame if its eroding faster than you like.


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## Dirt Engineer (Sep 12, 2012)

Rocks and dirt only. Especially if you're doing this on public land. Wood will always eventually rot away no matter what species it is. May take longer but will be worth it in the long run.


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## .WestCoastHucker. (Jan 14, 2004)

as a seasoned dirt jump builder, i never use anything other than dirt in the jump. stuff inside makes the jumps fall apart much faster and maintenance more difficult


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## roughster (Dec 18, 2017)

Yeah dirt jumps in a Jumpline in a park, rocks and dirt only. Jumpline on a trail? Assuming you’re not in a super wet environment, absolutely! As they degrade sometimes the jumps improve lol! (Get more “lippy”). If it’s a trail you will be doing annual maintenance anyways so when a log rots out and requires replacement or extra fill dirt, no big deal!


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## raisingarizona (Feb 3, 2009)

I suppose it's ok if you are good knowing that these structures are going to need to be rebuilt not too far down the road. This is where trail builders have to weigh in the pros vs. cons when making these decisions such as how much maintenance is acceptable or within reason, who's going to do that maintenance and how much more tread construction will be in this areas future? If this is a community trail system that's limited to X amount of miles then regular maintenance on features may not be a big deal, if theres plans for a fairly vast and extensive network you are going to want to be honest with yourselves on how many unsustainable features you really want to build. It's the old maintainable vs. fully sustainable thought process. Some of the previous posts are saying i's a no go or it's totally ok but it's unfortunately not that simple. This is why the IMBA has stressed the importance of sustainable treal design, if you want to be building more new stuff and continue to expand your network you don't want to get bogged down with maintenance projects every season and that's why it's often better to take your time and build features that will stand the test of time. You can see in plenty of places where jumps and features have gone the way of the Dodo bird because there isn't the resources to keep them properly maintained. Hazard County is one that immediately pops into my mind as an example.


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## roughster (Dec 18, 2017)

raisingarizona said:


> I suppose it's ok if you are good knowing that these structures are going to need to be rebuilt not too far down the road. This is where trail builders have to weigh in the pros vs. cons when making these decisions such as how much maintenance is acceptable or within reason, who's going to do that maintenance and how much more tread construction will be in this areas future? If this is a community trail system that's limited to X amount of miles then regular maintenance on features may not be a big deal, if theres plans for a fairly vast and extensive network you are going to want to be honest with yourselves on how many unsustainable features you really want to build. It's the old maintainable vs. fully sustainable thought process. Some of the previous posts are saying i's a no go or it's totally ok but it's unfortunately not that simple. This is why the IMBA has stressed the importance of sustainable treal design, if you want to be building more new stuff and continue to expand your network you don't want to get bogged down with maintenance projects every season and that's why it's often better to take your time and build features that will stand the test of time. You can see in plenty of places where jumps and features have gone the way of the Dodo bird because there isn't the resources to keep them properly maintained. Hazard County is one that immediately pops into my mind as an example.


Perfect post on this topic, cheers!


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## alex-henson (May 6, 2016)

Yes maintenance is key as noted above. There are a series of jumps a few guys built where I ride last year. Lots of downed wood inside. They look terrible, and now a year later essentially abandoned, are degraded and scarred the heck out of the area, and most unusable. The kind of stuff that if I were not a mtber, I would see and start to hate mtbs.


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## roughster (Dec 18, 2017)

alex-henson said:


> Yes maintenance is key as noted above. There are a series of jumps a few guys built where I ride last year. Lots of downed wood inside. They look terrible, and now a year later essentially abandoned, are degraded and scarred the heck out of the area, and most unusable. The kind of stuff that if I were not a mtber, I would see and start to hate mtbs.


Have you considered fixing them?


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## alex-henson (May 6, 2016)

roughster said:


> Have you considered fixing them?


Yes. I do bits of work on each ride.


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## roughster (Dec 18, 2017)

alex-henson said:


> Yes. I do bits of work on each ride.


Then why are they a mess a year later if they were abandoned? This is the part of the trail building conundrum I don't get. So many people want to help build "new" trails. Very few, if any, want to take the initiative to maintain what they have. I know why, because it has to be a conscious decision of working versus riding, and most people choose to ride.


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## alex-henson (May 6, 2016)

roughster said:


> Then why are they a mess a year later if they were abandoned? This is the part of the trail building conundrum I don't get. So many people want to help build "new" trails. Very few, if any, want to take the initiative to maintain what they have. I know why, because it has to be a conscious decision of working versus riding, and most people choose to ride.


Getting kinda OT there buddy. I'm not trying to complain, just saying the op why they might consider not using logs under dirt: it has the possibility to be extremely unsightly, it requires maintenance, and if you abandon it someone will not be happy to clean your garbage.

But to answer your question...

It's still there because nobody has cleaned it up. I do bits and pieces when I pass through but am not wholly responsible to clean other people's piles of garbage.


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## roughster (Dec 18, 2017)

Sorry don't mean to get off topic, but this point is salient to the OP's question. And to be clear, even 100% Dirt and Dirt/Rock combo features ALL require maintenance over time, period. Sure the interval _may_ potentially be longer for dirt/rock, but that also depends on the local environment, weather, presence of livestock, usage volume and patterns, etc. For examples, there is nothing more satisfying to a cow then walking all over a pure dirt jump / berm. NOTHING!

I am of the persuasion that we need to break the mental crutch of most MTB'ers that perfect trails are perfect forever and if not, it was the builders fault. We need to promote maintenance as just as glorious as new mileage. I see rider after rider go around branches and sticks in the local trails, complain about hoof prints while not doing a single thing about them. While I not only interrupt my regular rides to remove debris and fill in holes, I also specifically don't ride some sessions and just walk and clean the lines (we have livestock for a good chunk of the year) so it wouldn't even matter if they were concrete.

Sorry a bit rambling, *TLDR*: All trails require maintenance and fairly routinely even if built with 100% dirt and Dirt/Rock combo in a perfectly "sustainable" style.


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## alex-henson (May 6, 2016)

roughster said:


> Sorry don't mean to get off topic, but this point is salient to the OP's question. And to be clear, even 100% Dirt and Dirt/Rock combo features ALL require maintenance over time, period. Sure the interval _may_ potentially be longer for dirt/rock, but that also depends on the local environment, weather, presence of livestock, usage volume and patterns, etc. For examples, there is nothing more satisfying to a cow then walking all over a pure dirt jump / berm. NOTHING!
> 
> I am of the persuasion that we need to break the mental crutch of most MTB'ers that perfect trails are perfect forever and if not, it was the builders fault. We need to promote maintenance as just as glorious as new mileage. I see rider after rider go around branches and sticks in the local trails, complain about hoof prints while not doing a single thing about them. While I not only interrupt my regular rides to remove debris and fill in holes, I also specifically don't ride some sessions and just walk and clean the lines (we have livestock for a good chunk of the year) so it wouldn't even matter if they were concrete.
> 
> Sorry a bit rambling, *TLDR*: All trails require maintenance and fairly routinely even if built with 100% dirt and Dirt/Rock combo in a perfectly "sustainable" style.


Agreed. My example was a particularly bad example of unmaintained logs in dirt jumps requiring extra maintenance in the back end..... and probably not the best example. I'm sure logs could be used with reasonable results if proper care was taken, even if it wouldn't be my choice of building material.


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## aero901 (Apr 11, 2012)

Use all dirt or other non-organic material that will last, especially if this is in a public park. When it comes time to "fix" jumps that contain rotting logs, nobody wants to do it. Always better to put in more effort up front than taking shortcuts which will eat up more time/resources in the long run. See if the city will give you a truckload of dirt and someone to help spread it around with a machine.


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## jeremy3220 (Jul 5, 2017)

In my limited experience, dirt jumps require more maintenance than property built wooden jumps. Treated wood should last a few years with little to no maintenance. A dirt jump will wear/erode down noticeably within a few months. Obviously just using deadfall as filler isn't going to last long but building a wooden (treated or cedar) boxed landing then filling with dirt should last a while. My preference is all dirt but it's a lot of work.


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## .WestCoastHucker. (Jan 14, 2004)

aero901 said:


> Use all dirt or other non-organic material that will last, especially if this is in a public park. When it comes time to "fix" jumps that contain rotting logs, nobody wants to do it.


most of the time the maintenance requires pulling out the logs and rebuilding the jump anyway



aero901 said:


> See if the city will give you a truckload of dirt and someone to help spread it around with a machine.


 you'd be surprised how much dirt is already there on the ground. all it just takes a shovel to find it...


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