Got some firewood in North West London from chopping down a couple of large-ish Lailandi. Don't know what sort of firewood it makes. I can trim it and chop it up ready for collection. Be glad to get it taken away. If anyone has any good ideas on how else to advertise it I'd be glad to know. I'll try freecycle too. I'd prefer it went to one of you chaps with your fancy clean burning wood boilers than just someone who wants to send the energy up their Victorian chimney.

thanks Biff. I was going to keep some of the bigger, straighter bits for fence posts and things - and maybe for something more artistic like a Pergola. But there'll be quite a bit left over for someone to burn too.
If its allowed to dry out would the resin cease to be a problem?

I cut down some Leylandii last year. Largest was about 250mm diameter,(remember they were sold as hedging plants for suburban gardens, I fell for that one!). I thought I'd keep some large pieces for features in my loghouse.

No. Leylandii hartwood is naturaly durable. The tree is a hybrid of the Alaska yellow pine and the Monteray cypress. They both have a cocktial of chemicals that are toxic to fungi and the creatures that turn timber to compost. With small section timber there's a lot of the less durable sapwood, but I'd still not use any preservative. Just plant some more Leylandii so there's plenty of new timber to build a new pergola when the time comes.