What timber for building a flower box?

[flowerjoy]

Hello, I've been reading the useful messages - I hope you can help me also.  We are building 3 flower boxes 200 off the ground and 400 of soil and 500mm long.  We will cover inside with plastic and place a draining pipe out of box into the garden so there is no drainage on to the porcelain tiles (in courtyard).  We would like to know (with weight in mind also) of a nice looking timber for front and sides (rear can be sleepers). Merbau was mentioned but then I read of tannins staining  (the tiles).  What other wood can be used please that is not hellishly expensive?  Thank you. 

[JacobZ]

Hi @flowerjoy,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you join us.

There are a variety of timbers that you could use in this application depending on the characteristics that you are after.

Merbau would be an aesthetically pleasing, cost-effective option if you could protect the tiles. This could be done with GRUNT Black 140um Multi Use Plastic Film, which can also be used to line the planter boxes. Tannin leaching typically lasts a few months when exposed to rain, so it would eventually reduce to a point where you can comfortably keep them on the tiles without protection.

Some visually appealing, hardwood timber options, that unfortunately still leach tannins, but at a lesser rate to Merbau, are Blackbutt and Silky Oak. They are often available in Bunnings stores but are subject to availability in your area. If you were looking for these options, I would suggest contacting your local store to check availability, or to special order. These timbers would still require protection for the tiles but often produce less tannins than Merbau.

If you would completely like to avoid tannins altogether, you would need to look at H3-treated pine, which can either be painted or stained and varnished to create a look suiting your style. 

A good option if you'd like to stain and varnish the timber is 90 x 22mm Decking H3 Treated Pine.

If you'd prefer to paint the timber, 92 x 18mm H3 Treated Pine FJ DAR Primed LOSP would be a good option for you.

Let me know what you think and if you have any further questions.

Jacob

[flowerjoy]

Hello Jacob, thank you for your prompt reply.  I was leaning towards the H3 treated pine which I would paint, however, I have read the ERMA report by Dr D. Read discussing the public health issues surrounding the use of copper chromium and arsenic CCA treated timber.  CCA is a mixture containing copper chromium and arsenic which is injected into the wood (as you would know).  Arsenic is a known human carcinogen - would it not be prudent to just ban these products instead of making excuses.  As the 'healthy' wood is expensive, I will put on hold my decision to use wood and find out what other products I can use to make flower boxes (unfortunately).  Thank you again for your help.  

[JacobZ]

Hi @flowerjoy,

Unfortunately, due to the exposed nature of the timber, some form of pesticide and fungicide treatment is required to preserve external timber. 

Other treatment options can be used such as LOSP or Micropro. You could also use a composite product such as Ekodeck to give your flower boxes a timber look without the upkeep.

Let me know what you think.

Jacob

[flowerjoy]

Hi Jacob,  I've been reading about Ekodeck but can't find any mention of whether this product is strong enough for flower beds which will be 200ml off the ground and 400ml high with soil & about 60 - 75 cm long.  Also, can Ekodeck be joined with L3 treated pine at the back?  Thanks.

[JacobZ]

Hi @flowerjoy,

I can say from first-hand experience that Ekodeck is very strong. 

Having built decks out of it and packing a huge amount of decking orders over the years, I have no concern whatsoever with its weight-bearing capacity at this size as long as the frame is well-designed and adequate fixings are used.

There's no concern with attaching Ekodeck to treated pine as long as adequate fixings are used.

Did you have a particular design in mind? I am happy to have a look and give you some advice if you'd like.

Let me know.

Jacob