roof sheathing: anyone ever use pressure-treated plywood?

[bucktaker]

kinda late to your party but why arent you using galvanized posts, galvanized zee purlins, ??? On Norris Lake most roof systems are this way. I will be building one my self over my boat slip It will be 18'x32 gable roof
Pm me and we can share dock building tips

 

[Tollster]

The hardest part with plywood would be carrying it through the woods. Once at my stairs, it can slide on the railings while I walk down.

I do think I have found a good metal roof solution that will only cost a couple hundred more than asphalt, including freight. So I am going in that direction now. It would be 26 ga PBR panels 3' wide, which will weigh about 21 lbs in the length I need (they can custom cut to exactly what is needed, so I will order them to get a 2" overhang past rafter tails).

I am seeing mixed information about metal roofing on treated wood purloins, so I left a voicemail with the metal supplier to get their take. I am thinking I could put a strip of roofing felt down between the panels and each purloin and then use galvanized screws. But if that is still not recommended, I can probably go with regular wood on the purloins and not have issues (rafters and all else would still be treated).

If you can fairy it from the launch with your boat, it may make things a lot easier, same thing withs tools and what have ya

 

[sld]

Non-treated wood that is coated with a good stain / protectant will last a long time on the underside of a roof. Heck, most car washes around here have regular pine rafters exposed and they do fine. The key is the wood has to have a chance to get airflow and dry out. Trapped moisture is what is bad.

 

[EddieWalker]

Without seeing any pics of what you are doing, I would be very hesitant trying to work from a barge or anything floating in the water. How deep is the water around the dock? I've had good luck just putting a latter on the floor of the lake and climbing up it above the water. I've also built platforms around the sides of the dock off of the piers in the water. On every job, there is always that desire to find the easier way to do it, but I've found that those easy ways always seem to take longer and involve more effort then just sucking it up and getting it done. For me, I'll just haul everything to the job site from my truck. I've watched a crew of five guys working on a dock right across the water from where I was working, and just marveled at how much effort they put into getting their trailer full of wood right down to the edge of the water. They used different trucks and then brought in a tractor the second day. I was done carrying just as much wood by hand in half a day.



Eddie

 

[s219]

kinda late to your party but why arent you using galvanized posts, galvanized zee purlins, ??? On Norris Lake most roof systems are this way. I will be building one my self over my boat slip It will be 18'x32 gable roof
Pm me and we can share dock building tips

The main pier is built with 12" diameter treated pilings, driven 12-15 feet into the seabed, then the rest is underwater or above water supporting the pier deck and boatlift/roof. I have about 7-12' depth at low tide and 9-14' depth at high tide. The pilings are on the order of 30-40' long, and some impressive pieces of wood. So that's what I have to work with for posts. They are not perfectly lined up or perfectly round, or even perfectly straight, so my first task was to setup carrying beams and header beams and get the headers as straight and parallel as possible side to side. I just finished the last steps of that last night:



At this point I can start cutting rafters and laying them out.

The literature for the roofing metal suggests that 24" spacing for rafters and purlins is acceptable for uplift loads, but many of the roofs here use 16" spacing for both (which seems overkill). Some engineering analysis I'm looking at seems to indicate I can do 24" but insert an extra rafter at each gable (12" spacing there) and an extra purlin at each eave (also 12") to handle the most severe wind loads.

As far as static/snow/live loads, 24" spacing of rafters and purlins is more than enough, so it's really just the wind uplift that may drive me to narrower spacing or a couple extra rafters/purlins on the edges.

I was planning to nail the purlins to rafters with my framing nailer and 3-1/4" ring shanked galvanized nails (two nails per intersection) but may consider screws as that would increase the pullout resistance a bit more. Either that or add hurricane clips to every other purlin/rafter intersections as a backup.

 

[s219]

Without seeing any pics of what you are doing, I would be very hesitant trying to work from a barge or anything floating in the water. How deep is the water around the dock? I've had good luck just putting a latter on the floor of the lake and climbing up it above the water. I've also built platforms around the sides of the dock off of the piers in the water. On every job, there is always that desire to find the easier way to do it, but I've found that those easy ways always seem to take longer and involve more effort then just sucking it up and getting it done. For me, I'll just haul everything to the job site from my truck. I've watched a crew of five guys working on a dock right across the water from where I was working, and just marveled at how much effort they put into getting their trailer full of wood right down to the edge of the water. They used different trucks and then brought in a tractor the second day. I was done carrying just as much wood by hand in half a day.

View attachment 390107

Eddie

I tend to agree; I carried all the lumber for the beams down by hand, knowing it would take several hours (unfortunately it was a humid 100F day, but I drank plenty of water and took lots of breaks). I just got down to business and got it done.

For the rafters (which will be 2x6 @ 8') I will precut them and notch the birds-mouth up in my workshop, and attach a top gusset plate to each rafter. Then carry the pieces down to the dock in another 1-2 hour marathon. After a break, I can begin to glue/screw the gussets together, and stack the pre-assembled rafter pairs (essentially simple trusses at that point). Then the next phase will be to lift them into place and nail, one at a time. I'll worry about squaring them all up when I start putting up purlins, as long as I know the wind will be calm.

Then I'll carry down all the purlin lumber, and nail those up while squaring all the rafters. I plan to pre-mark all the rafters and purlins so that they are easy to line up while I'm in the air. Once the framing is squared up, I can slide rafter ties across the header beams and nail into place on every 2nd or 3rd rafter pair.

One side of the boat slip has a 16'x16' deck with plenty of working space and room for ladders. But the other side is only a 3' wide "finger" that also has steps and a lower platform. Once rafters are up with their 20" overhang, I won't be able to work on that side of the pier unless I put up staging. But I am pretty sure I can lift the metal roofing panels up from the deck side and over the ridge to the finger side.

I figure I can nail temporary "stops" on the bottom tail end of every rafter to act as a "catch" and straight-edge reference for the lower edge of the metal roofing panels. I'll be sure to line up the rafter tails with string when installing, so that they are all inline and give me a good straight edge for the roofing panels.

Since the metal is 26ga PBR panels, they will support my weight. So between the purlins and the panels, hopefully I can do most of the screwing from up on the roof and not need access from below with ladders. We shall see. I will likely pre-drill the screw holes to speed up the screw driving up on the roof. AS long as I am 100% sure of all the purlin spacings, it seems like I could pre-drill screw holes in the panels while they are stacked on their pallet.

 

[jimpen]

I'm not sure what part of Virginia you're in. I would suggest using something like these hanging brackets to put the rafters on. They should hold up to high winds. And probably help prevent damage if your in a hurricane zone.

At less than $2 a piece they shouldn't really effect the budget.

 

[bucktaker]

OK I see the pilings now. Mine is a floating dock that is anchored with cables to the shore and a sunken anchor in the lake. Around here it seems that the roofing systems are a galvanized 14 guage 8 or 10 inch Z purlin with a metal roof over that. I will see if I can come up with a picture. commercial marinas are built the same way

 

[s219]

I'm not sure what part of Virginia you're in. I would suggest using something like these hanging brackets to put the rafters on. They should hold up to high winds. And probably help prevent damage if your in a hurricane zone.

At less than $2 a piece they shouldn't really effect the budget.

Those are joist hangers. For rafters, we normally use little hurricane straps that help resist uplift. Before that, people would just toenail the rafters in, which is almost no help against wind!

I will probably use blocking to attach rafters. Block nailed down to header beam, then rafter nailed sideways into block. I just hate toenailing if it can be avoided. Then add the hurricane straps, which are face nailed to rafter and header.

 

[EddieWalker]

Sounds like you have a solid plan. The one thing you didn't mention and you haven't done on your beams yet was diagonal bracing from the post to the beam. Creating that little triangle in both directions will make a huge difference in cutting down movement. Every structure moves, the goal of every builder is to minimize that movement. Over time, movement will cause nails to come out, and screws to work their way loose. I never use nails on anything that is exposed to the elements because of how quickly they work their way back out. I also like to run my screws in at different angles for that extra bit of strength in locking everything together.

Eddie