1 October 1977
Brothers Ib Henrik and Torben Rønje found Rønje Bros, which has now developed into Sjælsø. Both brothers are state-authorised estate agents. From the start, the company specialised in the building of single family homes.

1980s
With the brothers as partners, the Rønje Bros estate agency was formed parallel to extensive construction work in the Sjælsø Huse and Sjælsø Enterprise companies.

1986
The company abandons the market for single family homes and instead turns to the business market, a step and total concept which Sjælsø Gruppen has since developed and refined.

1988
The estate agency business is divested. Focus is now solely on business in Sjælsø Gruppen and thus on property development.

Up to 1992-1993
Besides project development Sjælsø Gruppen activities now also comprise property investment and contract construction.

After 1993
The company abandons the role of estate agent and now alone focuses on its role as property company and on project development. Its core business is the provision of turnkey business projects to tenants and the subsequent sale of projects to investors.

1998
Sjælsø Gruppen A/S is listed on the stock exchange and acquires some 4000 new shareholders and an increased capital base, thus laying the foundations for new expansion and continued rapid growth.

2002
Sjælsø Gruppen A/S changes strategy as a consequence of lacklustre developments in the business market. In the following years, the company changes focus to home building and acquires centrally located and attractive plots mainly in and around Copenhagen. Sjælsø Gruppen A/S implements a large number of home development projects with great success.

2006
The company acquires Ikast Byggeindustri (IBI) and thereby establishes itself in the other Nordic countries, and also embarking upon international expansion.

2007
Sjælsø Gruppen A/S opens an office in Warsaw and quickly gets down to work on business, retail and residential projects in Poland.

Flemming Joseph Jensen succeeds Ib Henrik Rønje as president and CEO.
The company ceases to go by the name of Sjælsø Gruppen A/S, but is from now on marketed under the "Sjælsø" brand.

2009
Sjælsø completes a rights issue in order to strengthen the company's capital base. Ib Henrik Rønje and Torben Rønje resign from Sjælsø Gruppen A/S' Board of Directors. Furthermore Ib Henrik Rønje resigns from his position in Sjælsø in order to fully focus on Copenhagen Towers.