You build stuff. You build houses and additions and decks and kitchens. So why shouldn’t you sit down over a weekend and just knock out a company website?

One reason: mobile. Times have changed. According to a Pew Research Center Internet study last April (and these numbers only get higher this year), 55% of respondents said they use their mobile phone or other portable device as their primary source for access to the Web. Yes, their primary source for access to the Web.

That’s a big deal when it comes to website design shops, since they have to make sure a site looks just as good on a 27-inch screen as it does on a 3 1/2-inch screen. And that takes some skill.

If you’re wrangling your website yourself using one of those site-builder programs you get for free when you register your domain name, forget about mobile optimization. If you’re using static HTML to design your site, you’re going to need to build another, mobile-only, site to run alongside your primary site.

Now, I can build a house, but I probably wouldn’t want to live in it. And how that translates to you and your website is this: If you want brochure ware for a website that doesn’t convert, develop new business, or even show up in mobile search, then no problem, go in peace and build yourself a site.

But if you want a site that actually helps you sell your services, presents your company in the best possible light, and converts site visitors into clients, then you’re going to have to design it in a way that makes it easy for prospects to consume. And right now (and for the foreseeable future) that way is mobile, so think twice before you go it alone.