As Britain's construction industry reels from its sharpest downturn for seven years, it is companies that operate under longer-term contracts and have less exposure to London that are better weathering market uncertainty caused by the Brexit vote.

Builders' merchant Travis Perkins said on Tuesday the vote had created "considerable uncertainty" in the outlook for the building supplies market as it abandoned its target of increasing earnings by around a tenth this year.

The company's fortunes are closely tied to housing transactions and consumer confidence. Its customers range from big building firms to sole traders like plumbers and kitchen fitters as well as consumer DIYers, served through its businesses Wickes, BSS, Toolstation and Tile Giant.

The firm's announcement came as the Markit/CIPS UK Construction Purchasing Managers' Index inched down to 45.9 in July from 46.0 in June - the lowest reading since June 2009 and some way below the 50 mark that divides growth from contraction.

"It's just very difficult to predict what Q4, and Q1 and Q2 of next year looks like," said John Carter, chief executive of Travis Perkins, whose share price has fallen 19 percent since the June 23 vote to leave the European Union.

By contrast, construction company Morgan Sindall upgraded its outlook on Tuesday in its first update since the vote, saying it had strong visibility this year.

Its customers tend to offer longer-term contracts for bigger projects. They are government bodies who fund social housing, road projects or public space regeneration, education authorities planning new facilities and commercial customers who sign the company up for long-planned office refurbishments.

In the wake of the referendum shock, it is benefiting from what it described as a "high quality secured order book" worth more than 3 billion pounds ($4 billion). Around a third of that total is for the second half of this year, about another third for 2017 and the rest for beyond that.

"If we see any slowdown we'll react according. But we're not seeing anything at the moment in the markets we operate in," Morgan Sindall CEO John Morgan told Reuters.

Morgan Sindall's resilience in the near term echoes that of Kier Group, a company whose activities range from building power stations to outsourcing work for local councils. Kier said earlier this month that the vote to leave the EU had not affected its business.

LONDON FACTOR

Share prices of companies across the construction industry have been hammered down by the Brexit vote.

While Morgan Sindall and Kier have suffered, losing 16 and 15 percent respectively, they have fared better than housebuilders, which are more exposed to shorter-term consumer confidence.

Shares in Barratt, Persimmon, Taylor Wimpey and Berkeley are down 26, 20, 22 and 21 percent respectively since the referendum.

Exposure to London is also a factor for companies linked to the property market.

Much of the money in the capital's property market comes from foreign or domestic investors buying at the high end. They are more affected by Brexit-induced currency fluctuations and recent tax changes than in the rest of Britain where demand is mainly from British first-time home buyers and homeowners.

Only 10 percent of Morgan Sindall's housing business is in London and that part is not focused on the high-end sector, said the company's CEO. "People only talk about Brexit if we're here in London. Outside of London, it seems to be very much business as usual," Morgan said.

Bovis, which builds almost no homes in London, reported its reservation rate, where buyers pay a fee to take a property off the market, was flat in the first half of the year, suggesting little impact from the vote.

However London-focused estate agent Foxtons blamed a 42 percent drop in first-half profit on the Brexit vote, saying it led to a fall in transactions which is likely to last until the end of the year.