I just bought a 2 br townhouse. 1 br measures 10x10 and the other is 10x15. Would the value of the property decrease if I converted these adjacent bedrooms into one large bedroom?

If there are only two bedrooms, you better keep it as two. Not much of a Market for One Bedrooms. Everyone now wants a Computer Room; or a Library; or a Guest Room, or a "future" Baby's Room or all four. I could be wrong. I was wrong once before . . . . I just can't remember when !

Not only will the value go down you would be creating a white elephant. When you end up selling, and everyone does eventually, not only will you have to deal with the lack of buyers for a 1 bedroom but the appraiser will have to compare yours with other 1 bedrooms.

Make that one more vote for keeping it at 2 bedrooms, you will bring more buyers in by listing it as a 2-bedroom and the functionality will fit more peoples' lifestyles.

I agree. Do not make it a one bedroom if you want to maximize the value. Invest in the kitchen, bath and fixtures.