Yes, pipe; no, standard Romex. However, you may certainly create such a circumstance if you do it excessively over a short period of time. Normally, two parallel runs perpendicular to the ceiling joists would be used. If you need to run them parallel, just run them a few inches down the side of a joist. This is okay as long as you don't put any weight on the wire while it's up there.
Romex cable is designed to be buried in the ground. If you want to run it up on a wall or across a ceiling you have to buy special cable that is designed for this purpose. This is called "ceiling-hung" or "wall-mounted" cable. It's more expensive but it can be done with code approval if needed.
Here are some things to remember when working with overhead cable:
1. Use heavy-duty connectors on cable going into junction boxes. Do not use standard twist-on connectors because they will not hold up to constant movement up in a ceiling cavity.
2. Don't cut any corners here - get a professional electrician to install your system. Often times these jobs get overlooked due to their appearance or lack thereof, but they are not something you should try to do yourself. You could end up with a dangerous situation if you're not careful.
Yes, you can usually cut through joists, but you will also need to add trimmers and headers to the structure. As shown above, the trimmers run the whole length of the joists that are in place. Because they are simply 2x4s, the ceiling joists will not be able to support much weight. You should also note that if any of the trimmers' ends are less than 1/2" thick, then they cannot be used as header supports because they won't have enough surface area for proper bonding with the 2x4s below them.
If you were to use these trimmers as header supports, then there would not be enough material left over for the next ceiling joist. The solution here is to either add more trimmers or remove some of the existing trimmers to make room for new ones. Either way, you will need to trim some of the existing trimmers off so that they are within the 12-14" range required by code.
Once you have trimmed all the trimmers to size, you can install new ones and then repair or replace any that have been damaged during construction. It's important to remember not to use trimmers that are thicker than 3/4" for structural members over 11 feet long because they would prevent you from adding ceiling joists that are only 3/4" thick.
The best way to cut down large branches that might block your doors and windows is with a tree spade.
To withstand the horizontal stress in the existing state, the ceiling joists operate as horizontal ties. There are only four options for removing the ceiling joists and retaining the present roof structure. Because the connections are so important and frequently under-planned, they should be developed by a structural engineer. The options include: replacing the old ceiling beams with new ones of equal or greater size; adding additional support to the roof structure; removing the roof structure and replacing it with new material.
The first option is to replace the old ceiling beams with new ones of equal or greater size. This is usually the preferred method because it is efficient structurally and keeps damage to the building to a minimum. However, this is not possible if the ceiling beams are damaged or missing completely. If this is the case, then adding additional support to the roof structure is necessary. It may be possible to use salvaged or recycled materials in constructing new ceiling beams to match or contrast with the rest of the building.
The second option is to add additional support to the roof structure. This can be done by installing more supporting members under the existing ceiling beams or by adding new beams of equal size to the original ones. If the original ceiling beams are too small relative to the current support system, then they should be replaced with larger ones. Be sure to check with a structural engineer before making any changes to your ceiling structure.