Property damage exceeding security deposit

[TaRa Mehta]

Hello all,

My tenant reported that the garage door wasn't working. This was a perfectly functioning garage door when I handed the property to her. To address this maintenance issue, I sent out a reputed garage door company to look at it.  They told me that the garage door is beyond repair because it has been hit by something - causing the damage. They sent me pictures as well. The door now needs to be replaced completely. 

The cost of replacing the door is far more than the security deposit. The tenant's lease is ending this month and I'm not renewing. How do I mention this to the tenant in a way that she's informed that I'm on to her (and this is not a "repair" issue) ? I'm concerned that if I bring up the matter of withholding security deposit to cover the costs , they might cause more damage to the house prior to vacating this month. 

Any suggestion is greatly appreciated.

Thanks !