In The Boarding House, Mrs Mooney has found it necessary to leave her abusive husband and has managed to get a separation order from the church after he chased her with a meat cleaver. To provide for herself and her children she sets up a boarding house which she runs "cunningly and firmly." Her boarding house does have something of a reputation and the lodgers even call her "The Madam" which obviously has connotations for what may be going on there.
Even Polly, Mrs Mooney's daughter "her the run of the young men" who board there as there is little scope for her to marry well and her mother is intent on helping her to make a better life. It is her way of going about it that may be questionable but, in her own way, it really is the best she can do for Polly. She does not want her daughter to be left in a predicament similar to her own.
The boarding house then provides the backdrop to a desperate time when love and marriage where not necessarily commensurate with each other - the one did not depend on the other. Promiscuity is effectively encouraged in the interests of making the best choice from a poor lot. The boarding house is a microcosm of society - as seen from Mrs Mooney's eyes and others like her. It is a sad fact that her position and Polly's search for security and a better future are the result of the baseless society in which they lived. Bob Doran is also a product of his society, trying to be decent, wanting to do the right thing but overpowered by his confusion.
The boarding house and its context thus symbolizes the fruitless cycle of life in Ireland at the time.