Well-known big household insurers will normally consider non-standard risks, but the special terms they impose are rarely attractive. This tends to be particularly the case with thatched homes - which are regarded as unusually hazardous fire risks.
Norwich Union, for example, will consider all unusual risks on their own merits except for mobile homes. For most houses of non-standard construction, it will impose a 10-30 per cent increase in premium. In the case of thatched properties, the average loading is 100 per cent.
Using specialists will normally prove more cost-effective. Some types of unusual house are peculiar to distinct geographical areas. Local specialists have thus been able to develop high degrees of relevant expertise.
The presence of over 50,000 thatched homes in Britain has, in particular, led to the evolution of a formidable array of specialist insurance agents. Among those to enjoy good reputations are CGA Direct (based in Horsham), John Albion (Sudbury), Reedways (Ilminster), Country Thatch (Colchester) and Thatch- owners (part of Fenchurch group).
Catherine Crook, at the National Council of Master Thatchers' Associations, says: "Thatch insurance has now become so competitive that the specialists are offering some really good deals out there."
"Speaking as someone who lives in a thatched house myself, it is definitely worth shopping around, even among the specialists. There are such a range of discounts and excesses available that it's very much a question of horses for courses."
The thatch insurance specialists, which will normally be prepared to reimburse switching fees, are commonly able to provide contents and buildings cover for 30-40 per cent less than the traditional insurers. In extreme cases, normally involving larger houses, they can cost under half as much.
Some of the thatch insurance specialists will also consider covering other types of non-standard building. CGA Direct is particularly notable in this respect. It can cater for virtually any kind of unusual house and has a specialist scheme for listed buildings that will extend to any size of sum insured.
"The problem with having a listed property is that some district conservation officers will insist that any repairs are carried out with traditional materials, warns Richard Playle, director of CGA Direct. "You might therefore find yourself having to have oak window-frames, even though a pine equivalent would look just as nice."
Independent Insurance, which is willing to consider virtually any unusual risk, is also likely to be worth consulting for listed or other non-standard properties. It has insured everything from converted windmills and water towers to Cardinal's Wharf in London.
The company prides itself on not being blinkered by traditional rating formulas, and pays particular attention to individual circumstances. It will often send a specialist consultant to look at a property and perform a detailed risk appraisal. The terms it offers may well be conditional on implementing specifically recommended security devices and risk-management methods.
A spokesman says: "We would probably only fail to insure if there was no one to oversee the welfare of the property, such as in the case of a run-down squat."
Independent is also particularly notable for its Home 80/Fifty policy, which offers the most competitive buildings insurance rates in the entire market (from 8.5p per pounds 100 sum insured). Only those over 50 with homes built after 1980 are eligible for this.
St Paul International, which has even insured a lighthouse since entering the non-standard household market this April, also uses a case-specific underwriting approach.
Where historic houses are concerned, the market is dominated by two specialist intermediaries. Gauntlet Heritage only deals with buildings worth more than pounds 250,000 and contents of more than pounds 75,000. Bain Hogg, on the other hand, will also consider smaller country cottages, with buildings from pounds 75,000 and contents from pounds 25,000.