This is a very loose term, and covers a wide variety of building styles, some of which are well-established and unlikely to cause lenders to seek additional information. However, some kinds of non-traditional construction (some types of reinforced concrete, for example) have proved problematic, sometimes affecting the structural integrity of buildings.
Lenders will have different policies about which types of non-traditional construction they see as suitable for mortgage purposes. In addition, they will often take account of other factors that might affect the future marketability of the property when deciding whether to lend on a specific property of non-traditional construction.
If you want to buy a property of non-traditional construction, it is sensible to check the usual lending policy of any lender you are considering making an application to. If you are using a broker, they can often help you with this. You should also be prepared for the lender to want additional information including, potentially, specialist reports on any unusual property type.