I have a question for those of you who are skilled in the design of floor structures, etc. I'm considering whether it's possible to equip part of my garage with a storage loft. Since I absolutely don't want any columns in the way, it would mean the loft needs to be supported by four columns, one in each corner. The loft should withstand being walked on, but it's okay if it sways a little. I can attach three of the loft's four sides to the existing garage walls for stability, but I think it's inappropriate to load the walls more than that?
The question is: Is it possible to build a storage loft measuring 6.0 x 2.8 m, 2.3 meters up, that rests only on one column in each corner? How would you do this in the cheapest/easiest way, and what dimensions are required?
It is probably not a problem. The dimensions depend on what will be stored in the loft, i.e., the load it will be subjected to and how much sway you can tolerate. How you anchor the loft to the garage walls depends on what material they are made of. If the loft only needs to withstand a lighter load, about 200 kg/sqm, beams of class C14 45x145 mm c/c 600 mm might suffice. 200 kg/sqm and no sway require C24 45x170 c/c 600.
I'm only considering light storage, but if 45x170 is enough for a stable floor, I might as well go with that.
The existing garage walls are constructed with 45x95 c/c 600 with OSB+gypsum on the inside. As mentioned in the original question, the loft is only intended to cover part of the garage, so it's only possible to attach joists to three of the walls. However, one of these walls consists of a garage door opening, so it probably won't provide much support. What kind of joist do I need for the long side where I have nothing to attach the flooring to? Is 45x170 enough for the long side where I can also attach to the wall? If it's possible to use posts to support the joists for the long sides, what dimensions should these be? Attached is a quick sketch...
The load-bearing beam running through the middle of the garage must be made of glulam. With the same load conditions as before, 90x225 is an appropriate dimension. It will be easiest if you let this glulam beam rest on 2 columns made of glulam with the dimension 90x90. It's possible to screw together columns from standard construction timber as well, but a glulam column has the same width measurement as the beam, which is practical. To prevent the entire construction from becoming too tall, you should hang the cross beams in the glulam beam either with joist hangers or let them rest on a support rule that is securely attached to the glulam beam.
On the other side, the construction can be simplified. The more support or attachment points you can fit, the smaller dimensions you can use. It mostly depends on how you want the wall to look.
