Australia's multi-billion dollar building sector is facing significant change at a time when activity has started contracting because of the slowing pace of activity in the home building sector.

Boral is restructuring and CSR has moved to sell sugar and focus more on building products.

Boral shares remained suspended yesterday to allow the issue to be done to big shareholders at $4.10.

CSR's share price drifted down by 2%, or 4c, to $1.72.

CSR shareholders meet in Sydney today for the company's 2010 AGM.

Last night the Australian Shareholders Association called on chairman, Dr Ian Blackburne, to quit because of the company's recent losses.

That call will fall on deaf ears, but shareholders will want to know more about what they will get from the $1.6 billion to be received from the sale of its sugar business, and what it plans to do to expand further in building products.

In its presentation on Tuesday to analysts, Boral showed one slide with a helpful breakdown of the size of various markets in Australia in the construction sector.

These included construction materials, clay bricks and other products, timber and plasterboard: the total value in 2009 was estimated at more than $22 billion.

That's impressive and dominated by Boral, CSR, Hansen (UK), Brickworks and several smaller players, such as Adelaide and Brighton and the big Swiss group, Holcim.

These businesses dominate segments like cement, road building materials, quarrying, concrete, plasterboard and bricks, so acquiring one another won't happen because of competition problems.

The ACCC has made it clear in the past seven months that it will limit competition reducing acquisitions.

But an industry slowdown could force other companies to follow Boral into restructurings, or even sales of assets to new buyers from offshore, if they can be found.

Both Boral and CSR are big in home building products, such as bricks, tiles and ready mixed concrete.

But Boral also has grown aggressively in bulk building materials for the contracting and engineering sectors (aggregates, quarries, cement and concrete).

The biggest spend in this week's announcement was the commitment of around $200 million for a new super quarry south of Sydney, near Marulan.

It will eventually replace Boral's fading quarry at Emu Plains, in Sydney's far west.

The changes are part of new CEO, Mark Selway's attempt to put his stamp on the company, but they will be done at a time of mixed fortunes for the sector.

The slowdown in home building, thanks to higher interest rates, is offsetting solid growth in contracting and engineering and infrastructure, much of it financed by government.

The June Performance Of Construction Index (like the PMI for manufacturing) yesterday surprised with a sharp fall.

The index fell 6.8 points to 46.4 from May, according to the survey by the Australian Industry Group and Housing Industry Association released yesterday.

A reading below 50 shows the industry is contracting.

That was the fastest rate of contraction seen in the index for 10 months.

The six interest rate rises (which have slowed demand for housing finance) and the fall in demand for new houses with the ending of the first home buyers' grants seem to have hurt some section of the construction industry.

The fall came from the first contraction in demand for homes in 10 months.

"The housing outcome together with the continuing weakness of the apartment sector reinforces other signs of flat household spending," said director of public policy at the Australian Industry Group, Peter Burn.

"With employment and new orders falling in other sub-sectors, June marked a turn for the worse for the construction sector as a whole."

A measure of engineering work rose 10.4 points to 52.9 in June and commercial work advanced 1.3 points to 51.8.

Apartment building rose 2 points to 44, but was still very much in the doldrums.

Australian Bureau of Statistics for engineering construction work in the March quarter showed a mixed picture with public finance spending up, offsetting a fall in private spending.

The ABS said that seasonally adjusted estimate for the value of total engineering construction work done rose 0.3% in the March quarter, to $19. 833 billion, with the seasonally adjusted estimate for the value of work done for the private sector down 1.5% to $11.90 billion, and the value of work done for the public sector up 3.1%, to $7.93 billion.

That's another example of the way federal and state government stimulus spending has helped the sector.

Private capital spending figures from the ABS tell us there will be a surge in construction and engineering work in the current financial year.

But the outlook for housing depends on interest rates, confidence, jobs and bank lending.

Later today we will find the jobs market remains solid.