[robomartin]

> I need to build shelving units for a warehouse

I have to say it is hard to beat commercially available warehouse-grade shelving systems for this application. I'm not sure I'd consider a DIY solution unless I had nothing better to do with my time and the wood just happened to be laying around. You can go on eBay or Craig's list and find the kinds of shelving systems you see used by Home Depot for pennies on the dollar. Hardly worth the effort to build. Focus on your business.

I only see two scenarios under which building your own furniture makes sense:

  1- You want something that simply isn't available off the shelf.  
     Example: a custom entertainment center.

  2- You want to learn about woodworking.

I've done lots of #1 both for myself and as third party projects to earn money and fund other activities.

I find myself doing a lot of woodworking under the pretense of learning (or, more appropriately, teaching) these days because I am teaching my older kid how to build things. For example, a few months ago we built a custom wooden standup paddle-board. We started with cheap lumber purchased from Home Depot and ended-up with a beautiful fiberglassed wooden board that does pretty well at the lake. He learned a ton through that experience and we spent hugely valuable time together.

[superuser2]

My dad has gotten pretty decent at making furniture, and already owns tools for fun. He makes things himself in part because he likes it, and in part because he wants high quality craftsmanship, which comes much cheaper when you are the craftsman.

If you want IKEA-level furniture, it will never make sense to buy your own, but good handmade furniture gets expensive fast.

[AlexMuir]

You're right about the specialised stuff, and it's fairly cheap second hand. The warehouse is more a playground than functional though - I've set up a woodworking shop in a quarter of it, I have an area for mechanics and some desk space. I'm quite happy making things just for a break and because I enjoy it - I don't have kids yet, but I can't wait to teach them how to make things. Thanks