mud glorious mud....

..and the architect is the mud dauber wasp.

The colour of the tube depends on the source of the mud or clay the female wasp collects, scraping up soft mud with her mandibles a holding it between her front legs as she carries it to her chosen spot ( in this case Mum's garage!).
There she presses it into position and smoothes it out with saliva into a tube.
After 30-40 loads of mud are carried and smoothed to make the perfect chamber, she them provisions the nest with food for the young to feed on before laying an egg and sealing up the tube.
Meanwhile the bloke guards the cell to make sure no parasites take over the nest before the egg is laid and  tube is sealed.
A bouncer perhaps?