To save money however, my builder elected to use 18 inch i-beams joists made of oriented strand board (OSB) instead. ![]() My architect and his engineer specified 18" deep open-web trusses spaced 16 inches on center. I will also have two large cast-iron bathtubs upstairs and wanted to be sure their weight, when filled, would not be a problem. Our new home - still under construction - is a 3200 sq ft house with a much more complex design with much larger rooms downstairs. Now the second example and the cautionary tale. The only holes drilled through our 12 inch joists are little tiny ones that accomodate electrical wiring. ![]() Again, no need to cut holes thru those 12 inch joists. Meanwhile, all our upstairs plumbing is centralized over a single "wet wall" so all the drainage pipes run straight down. No holes had to be cut thru the joists to accomodate the ductwork. Parallel ducts T out of the top of this to reach the rooms that are at the back of the house. A soffit over my kitchen cabinets houses a duct that runs perpendicular to the joists from the HVAC unit to the back of the house. The HVAC unit also sits in the middle of the house (behind and just to one side of the staircase) so the AC ducts run parallel to the joists (i.e., each duct lies between two joists) to reach the rooms on either side of the staircase. The joists between the 1st and 2nd floor run perpendicular to the staircase and the widest room they have to span is only 14.5 ft wide. It has a central staircase with rooms on either side. (I know b/c several years ago I repaired the sheetrock in the dining room after we had a leaking pipe.) However, our current house is a very simple rectangular shape of only 1900 sq feet. In our current house, the joists are 2x12 lumber. I suspect (pray) they confer with qualified structural engineers whenever they are designing anything out of the ordinary.īut, let me give you two examples and tell a cautionary tale. And frankly, I rather doubt most architects - who are only required to take a very minimal amount of physics to get their degrees - really understand span load tables either. I would NEVER trust myself to actually try to determine the proper size joists for a house without help from a structural engineer. I have an undergraduate minor in physics and despite having recently read far more about joist loads and span table that I ever wanted to, and I can barely comprehend the subject. This is NOT an area that a novice should be playing around in. The whole issue of space between the floors for can lights and ductwork is secondary compared to making sure that your joists will support the load that is put on them. ![]() That fact alone means you will need thicker joists. I would lay odds that you intend to have large open rooms downstairs. ![]() If you needed to span a room that is 20 feet across with lumber of the same quality, you might need to use 2x12s that were spaced no wider than every 12 inches. A good grade of 2X10 lumber might be used for joists spaced 16 inches apart where the longest clear span is no more than say 15 feet. It also depends on the load you will be putting on the joist, how widely you space your joists, and the type of wood your joists are made of. The necessary joist height (thickness) depends in part on the distances you are trying to span.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |