On 26/04/2017 15:44, The Natural Philosopher wrote:
On 26/04/17 15:15, Stephen wrote:
Hello,

I am interested in making raised beds in the garden. I have not done
this before, so I have a couple of questions:

I am thinking of using wood due to cost, i.e. it is cheap. I see some
people use pressure treated decking boards like these:

http://www.wickes.co.uk/Wickes-Premi...-2-4m/p/101000

Is this the best timber to use?

wood will last about 5-7 years before it rots Whatever wood you use .

That isn't quite true if you use opepe. Sea defences often use it. it
can survive naturally in very hostile environments without treatment.

http://eastbros.co.uk/timber-species/opepe

Hell to work with since you have to drill and bolt everything together
it shatters if you try to nail it. The fences at my parents were made of
it 50 years ago and show no signs of deterioration apart from the
surface having turned grey with age. They were bargain offcuts from the
dye industry filter makers. Only wood that could stand the environment.

Buried it does eventually rot but very slowly and takes 20-30 years.

Is there a danger of the preservative leaching into the soil? I was
hoping to grow some vegetables to eat and do not want to poison
myself!

Some web sites suggest putting a plastic sheet between the wood and
the soil to prevent this contamination but other web sites do not
mention it; is it necessary?

Probably not necessary to prevent leaching but keeping the wet soil away
from the timber will extent the life of the wood considerably.

What is the best way to screw four pieces of timber together to make a
rectangular raised bed? I was thinking that I would need to sue a
piece of 2x2 in each corner and screw into these. Half of the 2x2
could be buried in the ground to anchor it.

However, is anchoring necessary: will the weight of the soil no hold
it in place?

It won't blow away if that's what you mean, but the weight of soil
inside will try to bend the planks outwards when you fill it.

Do I need to 2x2 at all, as I have seen some beds where the ends have
been butted together and just screwed through.

Use at least 3x3 fence post lengths at the corners.
2x2 will snap and/or rot away completely inside a couple of years.

Dig the posts in a decent depth too - do not underestimate the weight of
soil that needs to be held back (depending on how raised the bed is).

What is the best way of doing things?

Concrete blocks or bricks, and mortar

+1

--
Regards,
Martin Brown