Shophouses are not as straight forward to value as each shophouse has different gross floor area and the location of each shophouse matters too.
Nonetheless, the following are some macro trends which may be of benefit to you to give an idea of the market trends for each individual asset class.
The Trend Is Our Friend
Should I buy 99 Year Or Freehold Shophouse?
Which Districts Shophouse Should I Buy?
What Is The Performance Of Shophouse Rental?