Using Treated Pine - What is the "H" rating?

I needed to purchase some treated pine for 2 different projects. One was for some internal framing, which I wanted to protect against termites, and the other was for a gate post which would be outside and in the ground.

After talking with my local timber merchant I found I needed "H2" for the internal and "H4" for the outside gate post.

Here is a list of the different "H" ratings and their applications:

"H1" : To be used indoors, above the ground. Not resistant to termites.

"H2" : To be used indoors, above the ground. Resistant to termites.

"H3" : To be used outside, above the ground. Resistant to termites.

"H4" : To be used outdoors, in ground or ground contact. Resistant to termites.

"H5" : To be used outdoors, in ground with water contact. Resistant to termites.

"H6" : To be used when in constant contact with salt water.

Hope this clears things up a bit when deciding on the timber you need for your next DIY project. Make sure to ask your timber merchant for a more in depth description and application for each type.