Editing Warhammer Terrain Guide (section)

===Buying from Games Workshop===
So, let's get it out of the way. Buying terrain from GW is rarely cheap. You can sometimes get a lot for your money if you're buying the big box sets they occasionally put out, but in general, if you're using GW terrain, expect to lay down a big chunk of cash for your table.

That said, GW terrain has a few major selling points to it. The first is aesthetic - naturally, terrain produced by the same company that makes Warhammer will fit perfectly with Warhammer. The second is quality. Despite what some say, GW terrain tends to be extremely high quality, extremely detailed, and in some cases, extremely customizable. The last and most important feature of GW terrain, however, is intercompatibility. Especially in the 40k line, the more GW terrain you buy, the more interactions you'll find with it. 

GW kits are all standardized in a few key places - their walls and floors all work in intervals of 5", meaning a Sector Imperialis building and a Sector Mechanicus structure have the exact same height on each level. The plasma pipes they sell are also the exact same length, allowing them to serve as columns or to run exactly along a given floor segment with no excess, and nearly every 40k terrain piece has properly sized mounting points for the plasma pipes. 

For another example, the Galvanic Servohaulers set contains a flatbed trailer that's designed to carry the large crane included in the set. However, that flatbed also has the exact grooves needed to carry a Munitorum Armored Container, or the Genestealer Cults' Tectonic Fragdrill piece. The Fragdrill even includes a small tow point designed to go on the back of a Goliath Truck and connect to the trailer, letting the truck tow around any of these three things.

More recent kits of course stray from that 5" floor height (since most infantry can barely move an inch after ascending or descending making climbing or descending multiple levels awkward), like the Battlezone: Manufactorum/Command Edition terrain floor interval is at 4" while remaining fully compatible with other imperial kits, the Warzone: Fronteris kit, which expands upon Moon Base Klaisus kits has a mix of 2", 3", and 5" terrain pieces, the former two of which can be combined to make a 5" building, also compatible with previous imperial kits, and the Ork terrain for Warzone: Octarius which reaches 3" in height with the two doubled up main structures allowing for a big rectangular building of scrap (4 instances of the same corner can also be combined into a building with a square footprint if you're into that).
Nothing of this is cheap of course, but if you're made of excess money, time, and space you can make a sweet interconnected landscape.