How to build a wooden walkway 1.2m wide?

[Rick3]

Can I get away with two parallel 90 x 45 bearers1.2m apart(the width of the walkway) supported by short posts every meter along the length. Deck will be 90mm wide Merbau deck boards. Walkway will be only slightly above grade.

 

[Rick3]

I figured out that I can’t span a decking board 1m unsupported so I will have to run another bearer and line of posts down the middle. 

[JacobZ]

Hi @Rick3,

A warm welcome to the Bunnings Workshop community and thank you for your question.

Merbau decking is designed to be supported by joists spaced 450mm apart. With your design, even with the additional bearer running up the centre, the decking is spanning more than it's supposed to.

Have a read through How to understand deck span tables for a bit more information.

If you can provide some details on the overall length of the pathway, I am happy to help with a redesign that is in line with the recommended spans.

Let me know what you think.

Jacob

[Rick3]

Hi Jacob,

I really appreciate your response. You can gather I am very much a novice but have some recent experience extending an existing deck and repairing two existing decks that had rotted out. 

This project is just a walkway, not a deck, so I was wondering if the spans are fully applicable as it will not be loaded other than a couple of people walking along it?.  

Based on your input, given the maximum unsupported span is 450mm (I assume we refer to the span of merbau decking board), then it appears it would be most practical to make the walkway about 1m wide with 3 parallel bearers as I showed which will directly support the decking boards.   This would provide about 450mm between supports (with about 50mm overhang at each side).  I assume there is no need for additional joists in this case? Does this make sense or is there a better way?

The walkway will be about 21m long. Is there a better way than what I suggested above?

Thanks again Jacob,

Rick

[JacobZ]

Hi @Rick3,

No worries at all, everyone has to start somewhere. The recent repair work and extension will surely give you some great experience to look to when you start this project.

All span limitations related to decks will apply in this situation. Walkways, boardwalks, ramps and decks are all governed by the same principles and limitations on their materials. The principles developed for building decks ensure that wherever a point load is applied, it is adequately supported. Regardless of how they are used, they need to be capable of supporting a point load in all locations where they will occur. 

With this being said, adding the additional bearer and moving the two outside bearers in is a perfectly reasonable way of making sure your walkway is supported in all locations.

You will need to add some noggins along the length of the bearers at roughly 2.4m spacings. The main reason for this is that decking boards are not capable of bracing lateral forces which will come into play if the bearers are not attached to each other with framing timber. 

As they will not be there to support weight, you can use smaller materials such as this 70 x 35mm Outdoor Framing.

Let me know what you think and feel free to ask any further questions you have.

Jacob

[Rick3]

Thanks once again for great advice.  To make it simple I will do this job in 3m sections which I will reproduce 7 times to make the 21m long walkway.  I need to stick with a 1.2m wide walkway so my thinking is as shown below. Do 1m x 1m spaced tuff blocks with 3m long main bearers (A) connected and cross bearers also sitting in the tuff blocks.  I would do the bearer down the middle as noggins between each cross bearer screwed to the cross bearers.  The question is can I get away with this or do I need the central bearer to also sit on tuff blocks?  If this is no good I would likely go with your suggestion to have 3 main bearers with noggins every 2.4m or so along the length

[JacobZ]

Hi @Rick3,

Unfortunately, your design would not be suitable because in this scenario, the noggins, which are labelled "B" are being supported by joists, which have been mislabelled as bearers. 

Have a look at How to understand deck components, which should help clarify what characteristics define each structural member in a deck frame.

In this setup, you have three distinct types of framing members -

• Red - Bearers - Structural members that sit on posts or pedestals
   
• Green - Joists - Structural members that run between and are supported by bearers
   
• Yellow - Noggins - Non-structural members that keep the joists straight and add rigidity to the structure.

The basic issue with this setup is that a joist can't support another structural member. In this layout, the noggins are being treated as structural members.

I've had a good think about the best way to design things to minimise the number of posts and there really is no other way to do it. You're going to have to add posts along the central bearer run. 

Let me know if you require any clarification, I'm happy to assist further if required.

Jacob

[Rick3]

Thanks again Jacob,

Just one point of clarification regarding the joists in green in your diagram.  Can't I have these sit on top of the tuff blocks also and so treat them as bearers? Alternatively, if tuff blocks wont accommodate this, could I use wooden posts instead of tuff blocks that are large enough to have bearers run on top in two directions?

[JacobZ]

Hi @Rick3,

Yes, you can set the joists on the tuffblocks, which would make them characteristically a bearer, but then every noggin would need to be attached to them with joist hangers and connector screws to make it a structural connection and capable of supporting a load. If you run three bearers, there is no need for any joist hangers anywhere in the build.

I have done the math on previous projects and found that the cost reduction from having fewer posts/pedestals is more often than not made up for in the cost of additional joist hangers and hardware. This combined with the time it takes to install the hangers makes the additional posts, in my opinion, a better option.

Ultimately the choice is yours and I am happy to assist with whichever design you'd like to go with.

Jacob

[Rick3]

Thanks once again Jacob, very helpful to say the least,

I will go with 3 bearers, with a 1.2m wide walkway and 50mm overhang on each side. This means the bearers will be 480mm apart which I assume is ok? or if not, I can reduce walkway width slightly or increase the overhang to allow for a 450mm bearing spacing?

For the noggins, I assume I just use bugle screws to fix these in place?

Now for the posts.  The surface I will be putting this path over, is an existing path made of crushed granite.  This provides a very stable, well drained surface albeit with grass growing in it. I had in mind rather than using tuff blocks, using H4 treated 100 x 100 posts buried so they are slightly above grade, set with quick set.  I was thinking that 200mm high posts in this case would do the trick (with say 150mm below grade).  Your thoughts would be much appreciated?

Finally, the existing path follows a gentle slope.  I had in mind having the new walkway run with the exact same slope rather than making it level. This means I will use the current path level as my guide to set the posts.   Any issues with this?

Best regards,

Rick