Ask HN: Arguments for/against web templates

I am a civil engineer (hydrology). I've learned enough CSS, Js, PHP and MySQL on my own time to build what I want, how I want. My employer is interested in a website to handle floodplain queries. I'm comfortable with the project (especially since we are not an IT shop, and I was not hired for web dev, it's understood it could take some time). I've worked with geospatial data in OpenLayers and am learning the spatial functions in MySQL. My concern is: since we are not an IT shop, it seems likely someone else here will suggest using a ready-made template. My gut reaction is: I'd spend more time learning what the template was doing than I would if I just built from the ground up. So I am asking for arguments for and against using a web-site template for a geospatial database. Thanks for any help.