Casting for any & all ideas about using timbers that are exposed in and out. Mostly windows (structural - ha, ha) between timbers and we need best solution/practice to provide rain barrier close to outside and air sealing line close to inside.
Wood is the absolute best douglas fir KD down to 12% - all 12" x 12" dimensions. Finish on timbers to be Sansin that will 'breath' a bit. Five (5) foot roof overhang helps a ton for this house on Vancouver Island.
We're planning an air cavity behind the outer window trim to provide low pressure relief from wind driven moisture; cavity also drains any moisture that does get thru. Drains are all 3/8" or better so water won't want to hang around.
Debating the merits of peel & stick around window against timber or are we better off without it (letting timbers breath)? Flashing below window sill catches whatever does get thru during a major 'moisture event' and drains down.
Air sealing line is rod & caulk around windows just behind interior trim lining up with rubber gaskets thru wood joinery.
It sounds, and is, really kind of complicated - but necessary to meet requirements of 10 yr warranty. Not exactly timber framing, but welcome to building in the new century.
Arch and engineer pushing for epoxy coating the end grain of all timbers (hidden in joinery), but I think this is 'kiss of death' for the long haul.
Thanks in advance. Perplexed,

Randy,

timber showing is a good approach.

What is the infill going to be??? That would help with answering some of your questions.

Randy

How is it going out there? Based on my experience repairing brick mold and window sills on older homes, I would be more concerned with the end grain wicking moisture than I would be of sealing end grain with epoxy.

mike

'Infill' is actually window units - everywhere (hundreds of them). The window frames & units are well thought out = air seal just in board of inner trim, sloped sill and flashed OK.

End grain wicking. The objective is to prevent rot, period. That happens with equil moisture content (EMC) at or above 20-25%, i.e. when water sits for quite a while. I'm wondering how the joint will deal with water after a moisture event (storm against side of building). Assume the exterior gets soaked - water then wicks thru the tight joint into the interface area. Storm ends, now what? Does water sit and start rot or does it migrate. I want it to go away and migration thru wood is OK because the moisture event won't happen often. To prevent massive end grain checks I want to slow down end grain response time to make it match the face grain response. Basically that means an end grain sealer like the common Anchorseal.
I don't see how epoxy on the ends would help anything, but it certainly makes processing a pain in the patooty.

Randy,

keep us updated on the epoxy vs anchorseal debate.

My thoughts are avoid the epoxy like the plague -- I've heard stories of epoxy repairs that seemed to cause further accelerated rot.

Got the mill going yet?

Gabel

Borate rods or paste in the joinery? Inside the joints it won't leach away in your grandchildrens lifetime unless there is water actively running through them.

Randy
Two thoughts come to mind....seal the joint with caulking...where the cheeks of the tenon contact the beam or at the housing/beam interface.
Or
drain the mortice by drilling a 1/2 inch hole diagonally up and into the mortice from the far side of the beam
or
I know this is three, but how about slapping on a piece of ice and water shield cut to the tenon end dimensions before inserting the tenon.

As for sealing up the "wall" GREAT STUFF" Foam! ;-p

Bob

Gabel - still dialing in the saw & testing surface finish. Nice machine! Way out there specs for finish quality. 4 diff blade makers, lots of adjustments on the saw, wood vert vs flat face, etc. You figure out the permutations. Looking good though.
Did the pickled peppers come from you? No one sharing them yet.

The borate paste is nice thought Don, as opposed to wash (which won't soak in with dry wood). Borate rods in the plans.
The peel & stick or caulk ideas contradict best practices in several ways. P&S does same as epoxy, locks any water in.

Current solution proposal - now includes Sansin SDF as endsealer, a balanced end sealer instead of 'lock down'.
Mockup joints being made now, I'll keep you posted.
Maybe I'll get another degree out of this &*%$# house and all the science we are putting into it. Certainly make a neat TFG Conference session if someone is interested.
I'm sure learning a lot.

Hi Randy

I've been watching this with some interest to see what specific recommendations the veteran members have.
Having done that I'll take a few shots from the hip
Regarding the epoxy I have listened to similar debates among shipwrights, the debate is that you either entirely encapsulate the wood or leave a side to "breath". I have listened to the debate but have never seen any empirical evidence esp. on the let it breath side.
Another material used by shipwrights is "bedding compound" think caulking in a pail; this is spread liberally in the joint before assembly the purpose being to fill all voids and deny water from the joint altogether. Obviously a static structure is not subjected to the same conditions that a boat is but it may be worth a visit to the local boatyard. Or at least this is sufficient excuse for Steve and Gordon to pay you to drool over pretty boats (tell them I said so)

(Warning: exposure to other obsessive wood freaks may be hazardous to your financial health)

Now from a longtime Northwest house carpenters/remodelers perspective...that would be me
Two pieces of wood joined tightly together and exposed to the weather WILL ROT. Water that gets between two closely mated surfaces will be held by surface tension, will raise the moisture level of the wood at the juncture and provide a home for our friend brown rot fungus.
Obviously you cannot build joinery that is so loose as to let water drain freely so I think you have to do your best to deny the water entry in the first place.
What I was taught regarding exterior details was to make the thing work mechanically as best you can and then supplement with caulking.
Detail so that you leave no exposed horizontal (flat, level) surface or one that drains toward the building.
Make drip cuts on the underside of exposed members.
Make drip cuts or a hollow at post bottoms and elevate if possible.
Caulk the tops and exposed sides but never the bottom.

And a few words on caulking...
Always use the best you can. I usually use a Sikkens or 3M marine product.
Allow space for a volume of caulking that can expand with the material. A thicker bead expands less as a percentage of its volume as the wood moves and so holds up longer.
All caulking fails. Better caulking takes longer to fail.

Have fun..

J.E.B.

I wonder how this worked out for Randy and the building? I am looking at some preliminary plans of a few walls of glass and posts. No, interface details yet.

This seems like a difficult situation. Lots of rain and humidity here too.