The founder and chief executive of the instant messaging app Slack has said the company plans to expand its Dublin office in the future.

Stewart Butterfield said that right now the company is constrained by physical space and the heated property market has made it very competitive to get leases.

But he said as soon as the company can find a bigger office space it will be expanding and hopes to have 120 staff in Dublin this time next year.

He said the labour market here is also competitive but the company is used to competing in San Francisco, and is fortunate to be in the position right now where it is still considered cool, which makes it easier to recruit staff.

Watch the full interview with Stewart Butterfield here

Mr Butterfield, who also founded the image sharing website Flickr that was sold to Yahoo in 2005 for $25 million, was in Dublin to speak at Web Summit.

Slack is one of the fastest-growing technology companies in the world, and is valued at $2.8bn.

The company makes software that allows organisations to communicate internally using internal messaging.

It currently has 1.7m daily active users and a year ago had just a sixth of that number.

Mr Butterfield said in his view it is overstating it to say instant messaging is an email killer.

Email is a great lowest common denominator tool, he claimed, as it crosses organisational boundaries well.

But inside organisations it’s a terrible way to communicate, he added.

Asked about any future plans for an IPO or sale, Mr Butterfield said right now the company is focused on growth, but an IPO seems the most likely option going forward.

He added that it is going to be a long time before the company could consider floating on the stock market, as it is very hard to predict where it will be in the future.