Money from the DUP's Tory deal needs to be quickly translated into construction projects in Northern Ireland, a senior economist said.
The building industry suffered a 0.1 percentage point dip in the first three months of this year and with predictions of slowing growth the £1.5 billion package needs to become reality, Ulster Bank's chief economist in Northern Ireland Richard Ramsey added.
Projects like the York Street Interchange allowing the free flow of traffic between three Belfast motorways have been given the green light after the UK Government said it will provide £200 million for infrastructure development as part of the DUP agreement.
Mr Ramsey said: "Construction seems to be having a dip in the first quarter.
"Infrastructure investment has fallen quite significantly and we have heard a lot about the Westminster deal, with the DUP getting their £1.5 billion that goes for infrastructure and investment.
"When you look at these figures that is much-needed investment."
An economic bulletin said output in the construction sector had fallen over the first three months of this year.
Mr Ramsey added: "These figures are highlighting that that (DUP deal) needs to be quickly translated from paper to quickly get that money into the projects and getting moving on the projects."
The York Street Interchange will involve an underpass and bridge and is designed to improve links between the M1, M2 and M3. More than 100,000 vehicles pass through it daily.
Mr Ramsey said there still were not enough houses available and the construction industry needed a boost.
According to the Northern Ireland Composite Economic Index, published on Thursday by the Northern Ireland Statistics & Research Agency, economic output increased by 0.3% over the quarter to March this year.
The increase was driven by the services sector.
The production and public sector jobs index have remained relatively static. Construction fell by 0.1 percentage points.
Northern Ireland's annual growth rate is similar to the UK as a whole but below the Republic of Ireland.
Mr Ramsey said the country's economic output was still less than what it was a decade ago.
He linked much of the fallen output to the housing downturn following the bubble between 2005 and 2007.
"It was the biggest downturn in UK history so it is still recovering from that.
"Our recession was deeper, longer and the recovery was weaker than the rest of the UK and that is due to the type of recession we had which was highly concentrated on the housing bust."