Morgan Sindall subsidiary Lovell has won a £40 million deal to improve 6,300 homes in North-west Wales.
Lovell was chosen by social housing provider Cartrefi Cymunedol Gwynedd Cyf for the four-year programme in Gwynedd.
It will carry out a range of modernisation work to bring the housing association’s stock up to the Welsh Housing Quality Standard.
Work will begin in April and include improvements such as the installation of kitchens, bathrooms and heating systems as well as roofing and structural work.
CCGC chief executive Ffrancon Williams said: “This is only the beginning of our huge investment programme, and we are keen to maximise the benefits to the economy in Gwynedd.
“Recruiting locally and providing training opportunities are key when we appoint contractors, Lovell is already proving that it is committed to recruiting in Gwynedd and to working with businesses in the area.”