* Sector set to slump after lifting British Q3 growth
* Construction sector shares underperformed for past year
* Analyst says no visibility for investors until H2, 2011
* Social housing cuts largest blow to construction so far
By Lorraine Turner and Caroline Copley
LONDON, Nov 9 (Reuters) - Scaffolding and hard hats may be less visible in the UK next year as steep government cuts and a possible break in fiscal stimulus puncture a construction sector that has driven economic growth in the last two quarters.
Housebuilders, which make up about 15 percent of the sector, will be hit by the usual autumn pick-up in trading failing to materialise, and building activity could come to a near-standstill until the middle of 2011, warn analysts.
Uncertainty surrounding the UK's spending review has weighed on shares in the sector, which have underperformed the FTSE midcap index over the past 12 months even if the sector surprisingly propped up recent economic growth.
Construction output surged 8.6 percent in the second quarter and the sector accounted for a quarter of Q3 economic expansion.
But sentiment is at lower levels than the official figures suggest, with activity already slowing more than expected in October to its weakest point in 8 months.
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(For a graph plotting the construction PMI against GDP, see:
http://r.reuters.com/fas43q)
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"When you look at new orders in construction they don't seem to be supporting the sort of level of activity that we've seen in the last two quarters into the next two quarters -- in other words construction activity is going to tail off," said Trevor Williams, senior economist at Lloyds Banking Group.
Public spending cuts, uncertainty over fiscal stimulus and a lack of visibility is keeping investors at bay as analysts forecast 18 more months of pain.
"We had such a strong second and third quarter, with retrenchment on the public sector side and a stabilistation in private sector activity, we think the combination of the two means that we will fall back into recession next year," said Kelly Forrest, senior economist at the Construction Products Association (CPA).
Analysts agree that the middle of next year will be crunch time for contractors, and investors will get a much clearer picture of the winners and the losers.
"It's going to be a tough sector over the next two years...it's a big cloud on the horizon so why do I (as an investor) get interested in this sector when there is growth elsewhere," said Howard Seymour, analyst at Numis Securities.
"To me, second half of 2011, first half of 2012 is going to be the time when the trading is worse," he added.
THINK BIG
Companies will be able to mitigate some of the anticipated downturn through heavy cost-cutting to maintain margins as well as diversification into growing areas such as nuclear and utilities and competing for big-ticket projects such as London's Crossrail.
Large, diversified contractors such as Balfour Beatty, Carillion and Kier may emerge as winners, while traditionally pure UK contractors, such as Morgan Sindall that have focused on public work will suffer.
One of the biggest blows to construction is the government slashing its budget for social housing in half. More than half of contractors reported a drop in public new housing work in the third quarter, according to a CPA survey .
"They've said they'd like to deliver 150,000 affordable homes over the spending review period, but our analysis suggests that this is going to be very difficult," said Forrest.
The travails of social housing maintenance and building firms such as Connaught and more recently Rok, which announced on Monday it will go into administration after a series of profit warnings, have set alarm bells ringing in the construction sector but this is not necessarily an indicator of things to come for the larger contractors.
"You are progressively going to see the winners and losers, but I don't necessarily think that as you've seen in support services, you're going to see things explode," said Seymour.
Mortgage approvals fell to their lowest levels in seven months in September, as tough credit conditions persist and may even get worse.
In its latest report Investec downgraded all the mainstream housebuilders, citing a deterioration of the housing market and "serious risk of a double dip in house prices and land values."
Only 100,000 houses were built in 2010, down from the average run rate of 170,000 homes, and analysts expect the number to stay static into 2011.
"House builders have been really careful about restricting the supply of houses onto the market and I don't really see that changing," said Panmure analyst Rachael Waring.
"We're really looking at May or June next year before house builders could start opening new sites," she added.
(Editing by Sitaraman Shankar)