Hello,

I have a question about the interface between a stem wall and a timber (post). Most of what I have seen in the field is either the blade or stud that has been embedded in the concrete during a pour. On the site I am going to be building, there is a seismic requirement so I wanted to be clear about that as well. I spoke with a GC who recently did a TF structure on a slab on grade and he used anchors drilled and epoxied into the cured slab. Upon the curing of the anchor/epoxy, he used “all threads” into the anchors and then the resulting stud was used with a TimberLinx. I never knew that this was a viable solution (it was designed and called for by the engineers). The idea that a post might not line up with a stem wall on raising day is something that has always haunted me. Additionally, I also want to re-iterate that my design will be reviewed and stamped by a PE, but I wanted to hear what the pros here have to say about a drilled/epoxied anchor versus one that has been set in place during the pour. Just looking to hear what folks have seen in the field and the possible advantages and drawbacks of each. Of course, any concrete sub needs to be held accountable and due diligence should always be applied when the mud is poured.

Thanks in advance.

Hello Steve,

I will endeavor here, sorry for the brevity of this post... At least for my typical post replies...

I am taking that by "blad or stud" you are referencing the "tenon" at the base of a post?

These are never embedded in concrete and the few times I myself have seen such take place it is the indication of a "novice" at best doing the work and/or a contractor that is ignorant of the proper methods or showing little respect for the craft and proper treatment of wood...

First, I meant not to sound condescending, yet seldom find the methodologies of "GC" to have much merit at all, and seldom give sound advice when regarding the proper procedures of timber frames. The method related is one of a form that some do manage to facilitate in a reasonable manner, yet I find typically there are much better modalities to apply in tectonically active regions. Both traditional (my preference) and modern methods exist with the first having a history that is well known going back millenia.

I would, before going further, suggest that no matter what method is selected that a PE be selected that is familiar with traditional Timber Framing (I can recommend one, but own my biases here is strong.) I bring this up as you had mentioned and "Engineer" and like many (not all) "GC" if they are not familiar with timber framing too often lack the knowledge and creativity to over "best practices" and usually fixate on what they know and understand.

As for the frame "lining up" on raising day, I can assure you if a well seasoned Timberwright is consulted to design and facilitate the project, such issues are rare if at all occurring...

I have used structural adhesives of all form and manner from polyurethan to advanced epoxies to only mechanical methods and...of course...only traditional ones that maybe only slightly augmented with modernity. With a proper PE, you will be in good hands I am sure...

I seldom use, do not like nor promote OPC cements and find there use more a "convenience" for contractors and the like than actual "good practice." All one has to do is look at the OPC infrastructure of modern times and see the many flaws and lacking durability of this material in so many ways...Our bridges, as just one limited example, are mostly falling apart when made with "modern cements/concretes," while something like the Brooklyn Bridge is still going strong after heavy use over its 150 plus year life...It is made of some wrought iron, stone and "natural cements"/lime mortars... I only bring it up for the sake of exploring all the option out there for a durable foundation...I own my bias on this subject, yet have many years of studying and examining this subject. I actually like the use of mortars, and cements, yet seldom (virtually never) see it done well or with the appropriate modalities and actual "good cement work" is virtually nonexistent. What we have is mediocre at best and only in use because of the industries that promote it and our own collective laziness to demand better from the industry...which is slowly changing...

Jay, I'm guessing that the "blade or stud" he is referring to is probably metal embedded in the concrete. Some sort of knife plate connection. A little clarification may help Steve.

As to your question, it usually is permissible to drill in and epoxy anchors after the fact. Sometimes this can be preferable as it seems like things get hectic on a concrete pour and sometimes anchors get misplaced or forgotten. There is a certain advantage in being able to able to leisurely layout and place anchors a day or two after a pour.
J bolts have a comforting physical aspect, but this is only as good as the placement technique. If the concrete is not consolidated around a J bolt properly there will be voids. This all comes back to your contractor of course and hopefully yours will be diligent. Overall though, I prefer to epoxy things in after the fact, it's much more controllable.
I think that it going to be quite possible to find an after the fact solution to meet your engineering criteria, but I'm sure your engineer will be able to say for sure.

That would make more sense Sean, and I hope that is the case. I have seen contractors "embed wood post" into slabs more than once unfortunately...

If this is the metal "moment connections" that many PE are recommending then the concrete contractor will really have to be "top notch" to get them in the correct location...

Regards,

j

Sorry for the confusion. I definitely was referring to the metal embedded into the concrete. Additionally, I am aware it is also best practice to never have a post sitting on concrete. I also understand that all posts should be sealed with anchor-seal. It would be great if a concrete contractor could get them in the correct location, but it just makes more sense to perhaps drill and epoxy them.