It can be up to 30% more cost efficient for local authorities to build their own social housing rather than buy ready built 'turnkey' units according to an official assessment.
And new builds delivered by local authorities were also on average 9% cheaper than those by Approved Housing Bodies according to a spending review by the Department of Expenditure and Reform.
The review examined social housing build programmes in Dublin city, Fingal, Cork county, Galway city, Kildare and Mayo last year.
It found the average cost of a direct build by local authorities to be €230,000 compared to the cost of a turnkey, averaging €258,000 and rising to €300,000 in the Dublin areas and Kildare.
It cost Approved Housing Bodies more to build - an average of €258,000 - and they also had to pay more for turnkey homes - an average of €305,000.
The review concluded that in particular areas like Fingal and Dublin city it worked out better to build than to buy.
However, in Cork county and Kildare, where there was low output, there was little difference.
The review said that efficiency depends on location and delivery mechanism and called for more availability of data to help develop a strategy.
Overall, it found that some local authorities such as Meath, Louth and South Dublin deliver around 70% of additional social housing through the build programme, while for others such as; Westmeath, Offaly and Tipperary, it is less than 25%.
Usually, it is one third direct build and two thirds turnkey.
Local authorities typically build three bed houses while Approved Housing Bodies usually provide one bed apartments as nearly half of those on the housing waiting list are single.
In some Dublin areas social housing accounts for the majority of all new builds.
In the Dublin 1 area, which is the North Inner City, it was 62% last year, while in Dublin 10, which covers Ballyfermot and Cherry Orchard, it was 100%.