I am an architecture student so I have built quite a few models using cardboard. As it happens my final thesis is also about using scale models in architectural design and presentation.
Cardboard is a great material. It exists in various thicknesses, it´s cheap and easy to work with. You can build very intricate detail using cardboard, provided it is thin enough. I used 0.5mm cardboard to build a 1:200 spiral staircase once.
However, the problem is (as previously stated) that it may warp if exposed to moisture from glues, paints etc. The corrugated kind (the material cardboard boxes are made from) is especially sensitive. What you can do to minimise the warping is to close the poures of the material by spraypainting it with a base coat.
Often it is the glue you use that causes the warping. This is due to the fact that normal white woodworkers glue has resin particles suspended in water. The water is soaked up by the cardboard which then warps as moisture is absorbed. What you need to do is use an adhesive that is not water based. Bookbinder glue is often recommended.
You should also consider that cardboard often is not thick enough for a wall in 1:35. Therefore, I would recommend using a polyurethane sheet which is layered between two sheets of cardboard, often used in large architectural models. If you remove the cardboard or sections of it, you can scribe patterns (bricks)into the polyurethane or make shell holes etc.