Arson, is not an offence. This may be surprising but the Criminal Damage Act 1971 actually abolished this as an offence, but continue to allow the term to be used when charging someone. In Scotland, Arson is known as wilful fire raising.
The CDA 1971 covers offences of damage to other persons property (including by fire). Arson can be broken down to two categories, arson with a potential financial gain and arson as a malicious act.
Commercial insurance policies do not usually specify or include the word arson. They provide cover for fire (amongst other perils) this means that any cause of fire is covered. For example, if a neighbouring property catches fire and this spreads, you are covered.
If you set fire to your own property, whether for financial gain or not, you are not covered. Insurance is there to cover unexpected eventualities. You would be covered though if a neighbour set fire to their own property and this, unfortunately, spread to your property.
The one thing to watch out for is your excess, this should be around £200 to £250.

