There's a new box on the tick-list of the trendy South-east homebuyer. As well as the river view and parking space, there's a box saying "moorings".
Thames-side moorings used to be rare and unwanted, but the creation of small marinas means that some 20 major mooring sites now exist on the Thames from Abingdon and Oxford, through the commuter- belt of Windsor and Walton-on-Thames, Surrey, before the grittier confines of Brentford and Hammersmith. And there's no shortage of demand for private moorings near a sailor's home.
Greater personal wealth and the creation of lighter and easier-to-handle vessels means that vessel ownership has risen steeply since 1995. Developers have started to add berths to upmarket apartment schemes, especially in sought-after locations such as the Thames.
Central London's newest moorings are at the Riverside Quarter development in Wandsworth; 12 houseboat moorings were put in place at the start of this year. The location and facilities - mains water, electricity, pumped drainage, two telephone lines per berth, satellite TV links and parking space - mean that these sell at premium prices of £6,000 to £7,500 per metre (Humbert Leisure, 020-7629 6700). "Interest has been strong and we're going to best offers on some of them shortly," says John Mitchell of Humbert.
There are pontoons for those wishing to rent berths for no more than seven nights during a four-week period. If landlubbers want to settle for an apartment overlooking the water, they are on sale at £305,000 to £1.3m (Savills, 020-7409 8756).
In Fulham, the Imperial Wharf complex from developer St George will have a pier where residents can keep boats. Apartments start at £400,000 and rise to £4m for a penthouse (020-7610 9693).
If you want a new property that is more individual, you will find the going tough. There is a three-bedroom contemporary apartment with moorings at Strawberry Hill in Twickenham at £995,000, or £3,900 per calendar month to rent (FitzGibbon Residential, 020-8940 9920).
There are traditional period houses with Thames-side moorings, but you'll have to go to the fringes of London or outside it completely. Even then, don't expect bargains.
One of the least expensive examples on sale is a three-bedroom cottage at Eton in Berkshire with a small fixed landing stage and mooring rights, selling for £850,000 (Savills, 01753 834 600). But a larger Thames frontage will guarantee a seven-figure price tag.
At Bray in Berkshire, the five-bedroom River House, with a paved terrace and lawn leading down to a 145ft Thames frontage, is on sale at a cool £1.5m (Hamptons International, 01494 672 969). Just down the river is Doanee, an Edwardian house with contemporary interior. But it's the 105ft Thames frontage with steps leading to moorings and a boathouse that account for much of its £2.7m asking price (Savills, 01753 834 600).
At Wargrave, you'll find Elmwood, a modern thatched four-bed house with 128ft Thames frontage including a slipway and deep mooring - all yours for £1.85m (Savills, 01491 843 012).
Nicholas Brown of Knight Frank's Henley office says: "Moorings can add between 20 and 30 per cent to the price of a property if the right buyer comes along. River authorities are cautious about allowing more moorings to be built, so there's a finite number and sailing enthusiasts are willing to pay. I sold a house with mooring for £6m: without it, the price would have been £4m or so.
"The view from any house that has moorings is inevitably beautiful, and it's wonderful to be able to jump in a boat and go to a pub down the river for lunch. But in the summer the area can be busy and privacy is sometimes a problem. This can limit the buying audience."
And then there's the risk of flooding. Although most period houses on the river are elevated, and new homes with moorings will not get planning permission in flood-risk areas, insurance companies can be wary.
"Flood prevention measures have increased markedly across the UK in recent years, and we factor that into our assessment of the history and vulnerability of an area to flooding," says a spokeswoman for the Association of British Insurers.
"There are scare stories about properties not being insurable, but that's very rare. Floods get a lot of publicity, but actually they're exceptional. Anyway, properties with moorings are more likely to have owners who are aware and take precautions."Reuse content