Providing drainage holes below the bottom of timber, and spacing the timber up a bit from grade would both be good practice. AITC-104 Typical Details and Details to Avoid is a good resource for decay protection...
It's the superinsulated passive house foundations that are going for the thickest foam layers. 6" is light for some of those jobs- they're going for "thermal isolation" more than "thermal insulation". Agreed that it's similar to a cold storage facility... what would you do for that sort of...
Hi folks,
I'm a structural engineer, specializing in timber and used to designing pretty simple frost-wall foundations up in the tundra of New England. I'm looking to design more haunched-slab or raft-slab foundations at residential scale, both for warmer climates and for...
My understanding is that supporting timbers from points other than the bottom is a tricky art... NDS has rules for notching at supports, but glulams are only permitted to be notched to a tenth of the depth at most in the NDS. There are tricks like using fully-threaded screws as reinforcing, and...
jayrod, you make a good point- glulam mfg tells me that 12% MC is average out of their doors (and we should be able to keep it that way), which is better than I had in my head. We typically assume wetter stock, but this project won't be sitting around in anybody's yard for long. Unfortunately, I...
bones- I imagine one could get lamstock dried more, and that's an option on the table. The challenges there are keeping it dry until the building is finished and the cost of that special treatment. I'm holding out hope that the project team can come up with some shrinkage-tolerant details.
HotRod, thank you for diving in deeper here! I am looking at exactly that pickle, in which the steel and glulam both support the slab. I'm not familiar with compressed joints, is that something like https://wbacorp.com/products/bridge-highway/joint-seals/ ?
HotRod, I like the idea of an adjustable saddle. Building manager could advance jackscrews a bit seasonally for the first few years of occupancy until the timbers come to equilibrium. I'll propose that as an alternative to making them deal with the full deformation in the slab.
Across the pond, we're used to seeing 15-17% MC for glulams, which is typically not a problem because everything moves more or less equally. My concern here is the intersection of timber and steel and what that sudden discontinuity will do to the floor above (and some other components like...
molibden, if I'm understanding you correctly, you spec your glulams to be dried to 12% or lower? It makes sense that the mfg could put the lamstock in the kiln longer and be laying up at 12% instead of 15% MC...
Agreed, I'm generally using saddle-type hangers and paying attention to slotting any bolt holes that aren't right near the bearing surface to avoid creating cross-grain tension stresses with shrinkage. AITC 104 (Typical Construction Details and Details to Avoid) is a nice resource for this...
Hello all! Long time reader, first time poster.
I'm looking at a connection in which a deep (36") glulam timber tees into a W beam, with steel deck and slab over both. By my math, this timber will shrink by roughly 5/8" from its as-manufactured moisture content of ~15% to in-service MC of ~8%...
