Wood for raised beds

KeenOnGreen

We have just finished clearing our new allotment and need to build our raised beds.  The two options are (untreated) scaffolding boards, or planks which have been tannalised.  There seems to be a mixture of both on our plot neighbours.  Any recommendations for which would last longer?  The treated planks are actually cheaper than the scaffolding boards, but scaffolding boards look quite robust.  Whichever we get, we will line the inside with membrane.

Obelixx

In my last garden, I couldn't find scaffolding planks when we built our raised beds so I bough ordinary planed pine planks and treated them with Cuprinol.  They lasted years but eventually rooted.  As they did, we used treated roofing timbers.

The veg plot was, itself, a leveled patch of ground held up at the house end by a railway sleeper wall which we lined with black plastic to prevent chemicals leaching into the soil and also to protect the wood from moisture in the soil.  That was 20 years old when we sold it and still in very good nick.

Lizzie27

We used treated decking boards, lined inside with Terram (root proof fabric) half way up.
They're now 2 years old. Previously though we re-used old painted skirting/floor boards from the old house and they lasted for years before rotting.

KeenOnGreen

I'm still undecided.  The scaffolding boards that I see used look very robust, but they are not treated.  Cost might be the deciding factor, as we have a huge plot, and we will save hundreds of pounds if we go for the cheaper option.  Lining them with fabric/membrane does help to preserve them longer in our experience.

jenny794

I don't like using any chemical treatment on the boards in my veg patches. The chemicals must leech out and get into what you are growing and then eating. I am no chemicalphobe but I think it makes sense to be very cautious around your veg. There are some modified woods that don't have any residual compounds that can leech out. Accoya is the best - it is basically pickled wood so it does not absorb water hence no rotting and decay which gives it a much longer life than other softwoods. Its long lasting and safe for your food. 

NannyTreacle

We used decking boards from screwfix on allotments last year 10x2.4 meter boards £59.99 now £72.49 just checked https://www.screwfix.com/p/forest-patio-decking-28mm-x-2-4m-x-0-12m-10-pack/8004k  and i remember we got free delivery.

made 4 x 2.4 meter beds plus 1.2  meter ends for two of them,  my husband found wood for the ends of other beds. We bought two packs rest on allotment no2 (only half plots on our site) Hopefully they will last a few years. Picture allotment no1 taken on a sunny day in April 2019.  Potatoes are up and broad beans. Weeds were lurking!!