Wear and Tear Allowance

Hello, Can we claim wear and tear allowance on all furnished lettings or is there any restriction? What if, claiming the wear and tear allowance increases the loss? For example, rent received for a furnished room is $3,000 and expenses $4,500. In this case, can we still claim the 10% wear and tear allowance (it will increase the loss if we claim it)? Awaiting a reply. Any insights will be helpful. Thanks.