How to build a timber ramp over stormwater pipe?

[Jerrod]

I want to build a timber ramp over a stormwater pipe that crosses a concrete pathway next to the house. The ramp needs to be 850mm wide (it is not possible to make it any wider than 850, and I don't want to make it any narrower). The top of the stormwater pipe is 225mm above the path. So the ramp needs to go from 0mm (path level), up to at least 225mm, then back down to 0mm.

I was thinking of using some 200 x 50 H4 treated pine sleepers (cut on an angle and stacked on top of each other) to support some merbau decking boards.

I understand that decking is usually laid over joists at 450mm centres.

If I space the sleepers apart at 450mm centres, the merbau decking will have a 175mm cantilever (or overhang) on either side. I've never read of a deck with cantilevered decking, but since this ramp is quite low and the overhang is only 175mm, I thought that might be OK.

Am I wrong here? Is there a risk of someone standing near the end of a merbau board and it collapsing?

I could modify the design so that it uses three sleepers (instead of 2) to support the merbau decking. This would result in an overhang or cantilever of only 100mm. But maybe that is still too much? Three big sleepers seems like overkill for such a low ramp.

What if I put a galvanised angle bracket under each piece of decking, on the outside of each sleeper, to reduce the overhang distance a bit? (eg a Carinya 75 x 50 x 20 x 4mm Galvanised Angle Bracket would reduce the overhang to 100mm with 2 sleepers, or to 25mm with three sleepers).

The Sketchup image shows a section of the pipe crossing the path, as well as some dashed lines (guides) indicating where the sleepers would go, at 450 centres, starting from the centre of the ramp. 850mm is the total width of the ramp.

There are some metal standoffs supporting the stormwater pipe and keeping it off the path. Their locations (which are already set) make positioning the sleepers a little more tricky. They could be repositioned if necessary, but I'd prefer not to.

The ramp would have a gradient of 1:12 (or maybe 1:10) on either side.

[Jason]

Hi @Jerrod,

Welcome to the Bunnings Workshop community. We're so pleased to have you join us and trust you'll get loads of help and inspiration from our wonderful members for all your projects.

Could we please trouble you for some photos of the area? It might help members to better understand what you are working with. I'm certainly having a little bit of trouble understanding your set-up, and immediately wondered why the stormwater pipe isn't just underground?

Once you've shared some images, I can tag some helpful members and our resident Bunnings D.I.Y. experts to assist. 

Many thanks,

Jason

[EricL]

Hello @Jerrod 

Your ramp idea is excellent; However, I propose changing your sleeper layout to three sleepers instead of just two. This will give you full support along the entire length of the ramp and there will be no weak spots wherever you step. I've placed a sample image below to give you an idea of how it can be done. I suggest putting a gap of 350mm between sleeper's end to end. In order for the sleeper to clear the top of the ramp it will be necessary to add 25mm of timber at the top. Just keep in mind that whatever timber you use it must be at least treated H3 in order to withstand outdoor use.

To extend the life of the sleepers, I propose using CAgroup 50mm x 20m Bearer Protector G-Tape, this will prevent water from sitting on the on top of the sleeper. Also please note that the cut section of the sleeper must be sealed again using TWA Woodcare 300g Ecoseal Tanalised Timber Treatment. Please make sure to wear personal protection such as appropriate clothing, gloves, goggles and a paint rated mask when using this spray.

Please note that I also suggest putting noggins between the sleepers for extra support and to prevent them from shearing. Please note that measurements are for reference only, please adjust them to your needs.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

[Nailbag]

Hi @Jerrod 

This is a great project and well thought out. The design plan that @EricL has drawn up is excellent. He also obviously has some very clever technical drawings software that makes following his concept very clear. I would consider a few minor changes. Use single sleepers checked out to accomodate the pipe. Factor in that you will need some form of fixing timbers for a top board. If you have a reciprocating saw, you could make the cut out to that shape but only possible if the pipe could be removed and slid into position through all 3 frames. And finally, use a 140mm wide board for the top then 90mm wide ones down the ramps.

Nailbag

 

[Dave-1]

Good Morning @Jerrod 

I was reading through your idea and a story came to mind... When I was 12ish I built a bridge over the creek behind the house. I went with narrower spaced rails as my piers could only be so wide due to resources. Fast forward to someone using the bridge and not knowing the boards were cantilerer and trying to take a stolen motorbike over it... It didnt make it Saved the bike for my neighbours but lost the bridge type deal. So @EricL's suggestion is definently the way to go.

Without seeing how your land slopes/level it is, I will throw in something to consider.

I built myself a culvert for my stormwater in my front yard, I did consider a pipe but somehow I just ended up usiong stuff I already had. Plus I didnt want it to clog up.  Culvert for stormwater is my project. It has held up nicely in the past year with minimal maitenance being done on it.

So my suggestion is instead of rams up and over maybe build up teh ground if possible for a longer slower ramp and then drop down. I have dragged many loads of rocks ect via the path and even tho I stretched the slope as long as I could it still can feel a little steep.

Dave

[Noyade]

Hi @Jerrod.  I know you did say wood - but I'll toss a steel suggestion in as well.

Heavy steel plate that you regularly see on driveways - it would have to be cut by an engineering shop.

Bridge the pipe.

Weld and anchor the sections together.

Last forever.

Won't rot.

Take enormous weight.

Easy to clean under.

Just out on the bicycle and had a Sydney Harbour Bridge thought.

Cheers.

A very rough sketch....

[Jerrod]

Thank you @EricL that sounds like a good suggestion. I guess the reason I didn't want to use three sleepers was because I was originally thinking to make the ramp a much more gradual slope, like 1:10 or 1:12 (probably because I read all these websites about designing for wheelchairs etc, since I couldn't find any general ramp information back then). Putting in a third sleeper would increase the timber requirements quite a lot.

In fact, the picture I had in my head when I first considered building this ramp was a much steeper ramp like the one in your 3D diagram, which has a slope of 1:5 or 1:4. With such a short ramp, using a middle sleeper would be a simple addition.

The fact is that these two ramps are at the side of the house. The only time we ever go there is to raise or lower the exterior sun blinds in summer, and occasionally throughout the rest of the year to remove any weeds that have sprung up. So we don't really need a super deluxe, 1:14 ramp with handrails, grip tape and disco lights. We just want a ramp that will prevent us from tripping over the PVC pipe.

I'm not sure which ramp slope I should go for - something between 1:4 and 1:14 seems to be the range. A 1:14 slope would result in a 3.5m long ramp, which is excessively long, just to walk over a single PVC pipe. But is 1:4 or 1:5 sufficient? It looks OK in your Sketchup model.

Thank you for your suggestions of tape, sealing the cut timber and the noggins. And also for the links to specific products - very useful. I'd never heard of that spray before.

Thanks @Nailbag - I have recently been thinking of building a little box over the pipe itself, similar to your drawing. Then I could attach each side of the ramp to the box using galvanised gate hooks and eyes. That would allow disassembly of the ramp if the pipe got blocked. I still haven't drawn it up yet, but that's the general idea.

[EricL]

Hi @Jerrod 

The picture I've done is based on a 1meter length ramp and your provided height of 225mm. It would be technically too steep for a wheelchair user, perhaps a 2meter length ramp on each side would be more viable. I suggest doing another design and calculating the materials you'll be needing to assemble it. You'll then be able to tell if the project is within your projected budget. Generally speaking, the sleepers along with Pine decking would probably be more affordable rather than using Merbau. 

If you need further assistance, please let us know.

Eric

[Jerrod]

Hi @EricL 

Here is my 2m long ramp design. I've included noggins and a 400mm long sliver of extra sleeper on top, to reach the maximum height of 250mm. If I make it any less, there will not be enough wood to support the last piece of decking timber. Even now it might not be enough.

I'd be interested to hear your suggestions and feedback. I don't have to make it 2m long. This ramp is not being specifically designed for wheelchair usage. I'd be just as happy to make it 1m long or 1.5m long. That would certainly make construction easier.

I looked at the cost difference between merbau decking and treated pine decking and it didn't seem big enough to justify switching to pine. Although maybe all the hand sawing would be easier with pine. Does merbau last longer than treated pine decking?

(I do hand sawing because I prefer it. The only power saw cutting I do these days is using my jigsaw, recipro saw or oscillating multi tool. I'll be hand planing the end grain to get precise fit, using a shooting board. I might get a mitre saw in the future but no immediate plans yet.).

[EricL]

HI @Jerrod 

That looks fantastic, I love your idea of adding more timber at the top to make it go over the pipework. This should be more than enough to hold the weight of an adult crossing. Plus, the step up and down won't be so abrupt. The merbau decking panel is much better than the pine decking panel. 

If you need further assistance, please let us know.

Eric