How to build a raised garden bed with seating?

[nvelaga]

Hello experts, 

I am total beginner and planning to step up my DIY journey.  

I am planning to setup a raised garden bed with seating options in couple of places. Along with it i am planning to install part of my back yard with decking ( deck with will be partly on concrete slab ). I have attached my plan and the sample raised bed i am considering. 

I am looking for suggestions on how should i plan the project , tools needed and procure materials ? I am finding lot of information over internet and its confusing. 

Thanks in advance

 

[nvelaga]

thanks @JacobZ ,

if we need to use posts, does these suffice ? 100 x 100mm 2.4m Post H4 Treated Pine Sawn CCA - 2.4m , i think we need to cut them into half. 

Let's say i have used, retain-it posts. Is it easy to cover those with merbu cladding ? 

[JacobZ]

Hi @nvelaga,

If you need to use timber posts, anything that is H4-treated will work. The posts you have linked to are a good option, but they will not be the same colour as the sleepers. You can use a sleeper as a post, you'll just have to dig the hole wider to accommodate it.

If you use the Retain-It posts, cladding them with merbau will hide them extremely well and is a great way of doing it. There might be a very slight bulge where the merbau crosses the posts, but you can cut a shallow rebate in the back of the merbau board before attaching them to remove this bulge. 

Let me know if you have any further questions.

Jacob

[nvelaga]

Thanks @JacobZ , i am thinking to use the posts inside as shown in the community project - so that posts will be inside and hidden. 

Would you be able to guide me on below 

1. Timber screws that are needed 

2. Does 600 mm depth sufficient ? 

3. Do we need to coat those posts with rubber paint ? 

4. Diameter of the post hole ?

[J-P]

@JacobZ Would 3m sleepers hold without budging with just 2 retain it at the end?

[JacobZ]

Hi @nvelaga,

You can certainly mimic the style of anchoring @lcantem used in their Pallet timber raised garden bed. The one thing I would consider if you chose to use these posts is that you will have trouble concealing them with a decking board used as capping timber. If you are fine with this, then go right ahead.

You can use either galvanised batten screws or galvanised cup head bolts to attach your sleepers to posts. Bolts are usually a better option as they can be tensioned far more than a screw can.

600mm of depth for your posts will be sufficient. 

It's a good idea to coat your posts in a rubber membrane such as this Gripset Betta 1L Waterproofing Membrane Bitumen Rubber. It will add a layer of protection that will increase the longevity of the posts at a relatively low cost.

Post holes should be large enough that there is at least 100mm of concrete on all sides. With a 100x100 post, it should be 300mm in diameter. If you use a sleeper as a post, it should be 400mm in diameter.

Let me know what you think.

Jacob

[JacobZ]

Hi @J-P,

Yes, 3m sleepers can be used with Retain-It posts at either end when used in lower-level retaining structures such as garden beds, but you may experience some warping over time. Thicker 75mm hardwood sleepers will handle the pressure much better than thinner pine sleepers. You can also add a mid post to reduce the potential for warping over time.

Let me know if you have any further questions.

Jacob