Its exterior and interior door frames are also steel , as is the front door , which has been processed to resemble walnut .
The house 's most distinctive feature is its internal frame , which is constructed entirely out of steel beams .
feature 's exterior and interior door frames are also steel , as is the front door , which has been processed to resemble walnut .
The house 's most distinctive feature is its internal frame , which is constructed entirely out of steel beams .