How do you guys feel about mass timber for a 13-story project in Ohio?

You’re looking at a minimum of 12 to 16 weeks for finalized shop drawings before that CLT even hits the CNC machine. If your MEP guys are used to figuring it out in the field with a core drill and some rebar mapping, they're in for a rude awakening. We usually try to get our trade partners to sign off on the 3D coordination model at least four months out. Any change after the factory cuts the panels is a nightmare becuase field-cutting CLT often requires a structural engineer’s stamp and a lot of manual labor with specialized saws.

For the smaller stuff like electrical conduit or 2-inch piping, you can sometimes get away with field drilling if the engineer gives you a safe zone map. But for the big ductwork or plumbing stacks, those penetrations need to be factory-cut. We’ve had success using **BIM coordination** to the extreme—literally modeling every single hanger and sleeve. If the MEP sub isn't 100% on board with the digital twin, you’re going to have a lot of expensive mistakes that involve custom steel reinforcement plates and field-applied wood treatments. Regarding the base plates, putting them on elevated steel pedestals is definitely the right call. I’ve seen guys try to just use a high-strength grout bed or shims, but the moisture wicking from the concrete slab is no joke during the construction phase before the building is dried in. Wood is a sponge. If that glulam column sits in a puddle for three weeks after a heavy rainstorm in Columbus, you’re dealing with mold and checking before the dry-in is even finished. The **stand-off base** keeps the end grain high and dry, which is the most vulnerable part of the timber. Also, keep an eye on your firestopping. Since the CLT acts as the floor, the thru-penetrations need specific UL-listed assemblies that are diffrent from concrete. Most of the time it involves an intumescent wrap or specific mineral wool setups. It's a completley different workflow than just slapping some red fire caulk in a sleeve.

That four-month lead time for the shop drawings is wild. I’m just starting out, but I can allready see our MEP guys panicking when they realize they can't just 'find a spot' on the fly. If we do end up needing a small field cut for a stray conduit, what tools are acutally used? I'm worried about splintering the finish if we just go at it with a standard hole saw. Also, are the local inspectors usually up to speed on those UL firestopping assemblies? Since mass timber is still pretty fresh, I’m nervous about getting flagged for something that woud've been a non-issue with concrete.

For small field cuts, ditch the standard hole saw. Use a high-quality Forstner bit or a carbide-tipped hole saw if you want to avoid massive splintering on the exit side. For the bigger 'oops' cuts, I’ve seen crews use those Mafell chain beam saws—they’re pricey but cut CLT like butter and keep the edges clean enought for an inspector to acutally sign off on. Also, make sure your site super is religious about sealing the end grain. Even with those steel standoffs, moisture travels up the fibers via capillary action. A good wax-based sealer on those column ends saves a massive headache with checking and swelling later.

One thing you gotta watch out for is the acoustic treatment. Since the CLT is your finished ceiling and floor, you can't just hide the sound matting under a carpet and call it a day. We had a project where the vibration from the HVAC units on the roof resonated thru the entire timber frame because we didn't use the right isolators. It sounded like a drum. Also, regarding the moisture—get yourself a couple of industrial-grade moisture meters. Don't just trust the 'eye test' on the glulams. If those things get over 16% moisture content during the build, you’re gonna see some serious checking once the HVAC kicks on and dries the building out.

Don't sleep on the UV protection while the frame is exposed. If those glulams sit in the sun for weeks before the curtain wall is on, they’ll tan unevenly and leave you with 'ghosting' where the lifting straps were. I’ve seen crews use a temporary breathable sealer to keep the wood from graying out or getting water stains.

Also, double-check your tolerances on the Rothoblaas or Simpson hardware. If the steel base is even a hair out of plumb, driving those 12-inch self-tapping screws is going to be a massive headache. There's zero room for error compared to the wiggle room you get bolting steel to steel.