Question

There was no space in the drawing room. - Drawing room - uncountable
The sand on the beach was clean. beach - uncountable
Ruman met with an accident. Accident - uncountable
Are the above are correct?

Answer 1

The first and third are correct.

In the second sentence, "sand" is uncountable, but "beach" is countable.

Examples:
There are fewer public beaches in our state than in the state south of us.

There are more public beaches in California than in some other states.

There is less white sand on this beach than on that island's beaches.

Again ... it depends on meaning and how the word is used in a sentence.