A UK investment firm has raised £650M ($810M) of equity to build a £1.3B ($1.6B) U.S. and UK portfolio in the fast-growing industrial outdoor storage sector.

NW1 Partners, which counts blue-chip UK real estate investment firm Delancey among its corporate backers, has raised £550M in the U.S. and £100M in the UK, React News reported.

It has already bought $250M of assets in the U.S. over the past 18 months and said it will ultimately look to build a portfolio worth around $1.4B in the country. It has bought assets leased to companies like FedEx, the company said.

In the UK it has already bought 10 assets and plans to buy 10 to 15 more to create a portfolio worth around £200M. NW1 is planning to make a similar investment in the Netherlands, which would represent the first IOS investment strategy in the country, the company said.

IOS has grown into an asset class valued at about $200B in the U.S., Bisnow reported in January, and NW1 said it is betting that the sector follows a similar pattern to other niche asset classes like student housing, rented residential and life sciences: First something becomes institutional in the U.S., then the UK and Europe follow.

Fund manager Realterm raised $532M in May to recapitalise a 61-asset portfolio across the U.S. at a valuation of $1.2B.

In the UK, investors like Moorfield and Blackstone have invested in the sector, and Cerberus is investing in IOS in Europe.

Industrial outdoor storage essentially does what the name suggests, providing outdoor storage space for machinery like truck or van fleets or manufacturing equipment. Investors like NW1 are taking the strategy of creating large portfolios of smaller assets, which are typically located next to larger industrial sites.