PostgreSQL/PostGIS Geom to JSON with Inner Join to another table

I am currently producing JSON from a database successfully using the following query:

SELECT row_to_json(fc) FROM ( SELECT 'FeatureCollection' As type, array_to_json(array_agg(f)) As features  
FROM (SELECT 'Feature' As type, ST_AsGeoJSON(lg.geom)::json As geometry,
row_to_json((SELECT l FROM (SELECT extent, activationid) As l)) As properties  FROM hat.projectsgeom  As lg  
WHERE activationid = 'HOT-0001' AND agency = 'HOT' AND type = 'activation') As f )  As fc;

However, I am stuck when I try and use INNER JOIN to another table.

This is my attempt so far ..

ERROR: relation “activations.activationid” does not exist

LINE 5: INNER JOIN ( select * from hat.activations.activationid) zz …

SELECT row_to_json(fc) FROM ( SELECT 'FeatureCollection' As type, array_to_json(array_agg(f)) As features  
FROM (SELECT 'Feature' As type, ST_AsGeoJSON(lg.geom)::json As geometry,
row_to_json((SELECT l FROM (SELECT extent, activationid) As l)) As properties FROM hat.projectsgeom  As lg  
WHERE activationid = 'HOT-0001' AND agency = 'HOT' AND type = 'activation') As f )  As fc
INNER JOIN ( select * from hat.activations.activationid) zz ON (hat.activations.activationid = hat.projectsgeom.activationid );

I have tried a number of variations, I think this is close, but I cannot get a result ..

What do I need to change in the second query to get the Inner Join to work properly and return all fields form the second table?