Usually the appraiser notes the report or makes the value subject to a specific repair or just makes a comment that the carpet is dirty or soiled. If the carpet is destroyed where there are areas that the carpet has excessive wear and it could be construed as a health or safety issue, the underwriter can require it replaced. If it's a conventional appraisal, most generally it would not have a significant effect on value knowing the buyer is buying it as it, or the appraisal could estimate the cost to replace the carpet. If you are wanting to finance using either a FHA,USDA, or VA home loan, I have seen the underwriter require the carpet replaced unless it had areas that the cement floor was exposed. If you are selling your home, be prepared as the buyer may request the carpet be replaced.