Stick framed cold roof

[Brilton85]

Hey all, so I joined a few months back and have really enjoyed what I have been reading. A bit of a primer, I am in the infant stages of planning my home. I am doing the Northmen Guild timber framing course in 7 weeks and one thing I know for sure is I won't be using SIPs. I want to have stacked, scribed walls that are then wrapped with stick framing to really lock in the heat in winter, like those in "Birth of a Wooden House" but I am worried that may create some issues with the roof.

I am getting hung up on a couple design issues in my head but the biggest is the roof. I don't really want trusses or a lot of large timbers in my roof and neither does my wife(the real decider of all these things). My plan was to build up the walls and gable ends with stacked logs(aforementioned style) and then stretch a laminated beam across to either end with 2x12 rafters comprising the roof structure to allow for a very open feel in the second story. We are also heating exclusively with a soapstone wood stove so to prevent drafts, we want the house as sealed up as possible as the winters in AK can get a little bonkers.

My question is basically this: with SIPs, a cold roof is basically required, no? With that in mind, is it good practice to run 2x12 rafters off the laminated beam and do a cold roof off of that? If it WOULD work, would it meet code? Keep in mind, with these soapstone wood stoves, more often than not, you have to keep a kettle of water on the stove because it dries the air so badly. So between that and all the exposed wood, I don't think water vapor is much of a threat in winter. But code is code. Again, I want the house sealed up as tight as I can but if I have to do bird block in the rafters then I need to do it. Where we live doesn't really have building codes unless you want it zoned residential instead of recreational but this whole simplifying journey I'm on is about excellence in the process more than just the ends, and I want to do it right.

I appreciate any advice you seasoned pros might have. Thanks.

[Brad_bb]

1. You can put your location in your profile and it will show up in each post.  It helps people answer questions with your conditions in mind.  I know you said AK in your actual post, but for future posts...
2.  I wouldn't call myself a pro, but I've been through a few builds now.  I like using SIPS on the roof.  They are excellent insulation and sealing, and get you under roof fast.  I don't like SIPS on walls because I've ended up changing electrical a lot as we go along.  You always find some stuff you forgot of didn't think of, or a better way, and modifying stick framed 2x6 walls that you foam is much easier than SIPS.  If you're worried about thermal bridging with stick framed walls I recently saw a new product that is and engineered stud that has foam molded in it to prevent bridging.
3.  I don't understand your laminated beam?  Is this like a tie beam?  Are they just on gable ends or spaced along the building?
4. You ask if it will "meet code" and later say you have no code?  Which is it?  That sounds like a question that can only be answered by knowing your municipalities codes and getting plan approval.  
5.  You mentioned "bird block"  I don't know what that is or why you'd need it?  Perhaps you can do a drawing of what you are thinking?  
6.  If you're taking a timberframe course, why not do a traditional timberframe?  In a typical bent, you'd have principal rafters, a tie beam, and either king or queen posts.  In that type of bent, you'd run purlins between bents and then run your timber rafters over those.  Like this:


 
In another design, you'd have all common rafters sitting on top plates and a ridge beam, like this:



 
The sips sit on top of the rafters.  One thing I've learned is to top the rafters at the wall's top plate.  Do not overhang the rafters (rafter tails).  The reason is that you don't want rafters poking through to the outside because it is really hard to seal where they come through, especially as the timbers dry and move.  It's better to stop them at the wall, sheath and insulate so your building is a tight envelope, then add rafter tails/overhang on the outside for looks or rain shedding  etc.  The photos above show overhanging rafters, which I'd never do again.  Very difficult to seal.  On subsequent timberframes, we did the rafters flush with the wall, sheathed and insulated, then added rafter tails/overhangs on the outside.
7.  I really like the SIPS on roofs.  Insulate and sound deaden very well.  I had them installed by a good SIPS installer. There are some tricks to a good quick installation as well as some specialty tools for preparation and lifting that my installer made himself, that makes the job go fast and is done well. Trying to install yourself with no experience would probably be a bit challenging.  
8. I've done cold roofs with all.   We have cold winters and hot summers.  A cold roof is an added layer of insulation and moisture barrier/removal tool.  My roofs have gone like this:
Sheathing layer on top of rafters (wood T&G in my case or drywall).  Then a layer of roof paper (UDL50 in my case). Then a horizontal grid of 2x4's going up the roof every 2ft.  This does two things, It supports the SIPS, and it creates a cavity to run electrical (conduit in my case) across and over the roof.  Then the SIPS.  Then another layer of roof paper.  Then a grid of vertical 1x every 2ft.  Then a layer of 1x horizontally every 2ft.  This is your cold roof space.  The first layer is vertical so if any water ever gets in there, it can run down the roof paper on the SIPS and out the bottom.  Here's what the cold roof grid looks like:


 

[Brilton85]

1. You can put your location in your profile and it will show up in each post.  It helps people answer questions with your conditions in mind.  I know you said AK in your actual post, but for future posts...
2.  I wouldn't call myself a pro, but I've been through a few builds now.  I like using SIPS on the roof.  They are excellent insulation and sealing, and get you under roof fast.  I don't like SIPS on walls because I've ended up changing electrical a lot as we go along.  You always find some stuff you forgot of didn't think of, or a better way, and modifying stick framed 2x6 walls that you foam is much easier than SIPS.  If you're worried about thermal bridging with stick framed walls I recently saw a new product that is and engineered stud that has foam molded in it to prevent bridging.
3.  I don't understand your laminated beam?  Is this like a tie beam?  Are they just on gable ends or spaced along the building?
4. You ask if it will "meet code" and later say you have no code?  Which is it?  That sounds like a question that can only be answered by knowing your municipalities codes and getting plan approval.  
5.  You mentioned "bird block"  I don't know what that is or why you'd need it?  Perhaps you can do a drawing of what you are thinking?  
6.  If you're taking a timberframe course, why not do a traditional timberframe?  In a typical bent, you'd have principal rafters, a tie beam, and either king or queen posts.  In that type of bent, you'd run purlins between bents and then run your timber rafters over those.  Like this:


 
In another design, you'd have all common rafters sitting on top plates and a ridge beam, like this:



 
The sips sit on top of the rafters.  One thing I've learned is to top the rafters at the wall's top plate.  Do not overhang the rafters (rafter tails).  The reason is that you don't want rafters poking through to the outside because it is really hard to seal where they come through, especially as the timbers dry and move.  It's better to stop them at the wall, sheath and insulate so your building is a tight envelope, then add rafter tails/overhang on the outside for looks or rain shedding  etc.  The photos above show overhanging rafters, which I'd never do again.  Very difficult to seal.  On subsequent timberframes, we did the rafters flush with the wall, sheathed and insulated, then added rafter tails/overhangs on the outside.
7.  I really like the SIPS on roofs.  Insulate and sound deaden very well.  I had them installed by a good SIPS installer. There are some tricks to a good quick installation as well as some specialty tools for preparation and lifting that my installer made himself, that makes the job go fast and is done well. Trying to install yourself with no experience would probably be a bit challenging.  
8. I've done cold roofs with all.   We have cold winters and hot summers.  A cold roof is an added layer of insulation and moisture barrier/removal tool.  My roofs have gone like this:
Sheathing layer on top of rafters (wood T&G in my case or drywall).  Then a layer of roof paper (UDL50 in my case). Then a horizontal grid of 2x4's going up the roof every 2ft.  This does two things, It supports the SIPS, and it creates a cavity to run electrical (conduit in my case) across and over the roof.  Then the SIPS.  Then another layer of roof paper.  Then a grid of vertical 1x every 2ft.  Then a layer of 1x horizontally every 2ft.  This is your cold roof space.  The first layer is vertical so if any water ever gets in there, it can run down the roof paper on the SIPS and out the bottom.  Here's what the cold roof grid looks like:

I will add my location as we haven't moved up there yet but we have property. 
Regarding question 3: the laminated beam would span the length of the building and secured into the gable ends.
Question 4: code isn't required to inhabit but affects how the property is zoned. So if you don't want to build to code, it's generally classified as recreational property and not a residence. I plan on dying there but should I have to sell, I want to get top dollar as a residence. 
Bird block are boards between rafters on the eaves with a hole drilled in them and netting over the hole allow air but prevent bird and bugs from making it in. My question is, if moist air can traverse through a SIP with the aid of a cold roof, would it traverse through a stick framed structure in the same way should it have a cold roof?
My wife isn't crazy about trusses and traditional timber frame ceilings. It's been hard enough to get her to agree to move. I'm not going to push it. 

Thanks for your reply. Trying to take in all ideas. 

[btulloh]

You can put any kind of finished ceiling under the trusses or rafters.

[Brilton85]

@btulloh true. But then why go through all the effort to make big beautiful trusses in the first place?

[btulloh]

To keep your wife happy?  :D

I guess you just go with regular ol' flat-bottom trusses and put drywall on the ceiling?

T&G on cathedral trusses or under the rafters?  

The cold roof question, or roof system in general is certainly worth designing correctly, but I'm not sure what options are available for the interior look other than finished ceiling or exposed members.  I'm sure you'll corral all the variables and end up with a good design and the visual you desire.  I'll be looking forward to following your progress and seeing the finished result.

[Brilton85]

@btulloh isn't it funny how we overthink things? Traditional trusses hadn't even occurred to me. I'll have to look more into that and see how we can incorporate those in to the design. She wants an open feel but with drywall ceilings, so this has been REAL fun to design with her. 😳

[btulloh]

Scissor trusses to split the difference.  Open feeling, not as much air volume to heat.

Over-thinking is never far off on the Forestry Forum.  I believe it is a prerequisite for membership.  

I would call what you're doing "getting it right".

[Brilton85]

@btulloh thanks! Between the two of us, our "must haves" are creating some fun design issues so I'm constantly going through the build process in my head and on paper as I learn more and more and want those issues ironed out as much as I can leading up to the build. I've been to several SIP homes and I'm not crazy about what I've seen so I'm opting to make the place far beefier than it needs to be for the sake both being in a seismic area, and the aesthetic I want. I'm kind of going for the "Viking lodge" vibe. My wife finds it trying to be away from big cities for a weekend but she always enjoys our trips to AK. 

[btulloh]

Sounds like a "Green Acres" situation.

Perhaps run it all by an architect/engineer when you've finalized all your must haves.

I just hope you'll keep us all up to date as the build progresses.

[Brilton85]

@btulloh Oh I will for sure. I'll need lots of help along the way. I figure I have it about 90% figured out but that last ten is a gulf. 

[Raider Bill]

 

 

 

 

I used trusses on mine. 6-12 roof and 4-12 great room angle. I like the look.
Was able to buy all my trusses for the price of one timber frame truss.

[Brilton85]

@Raider Bill the rest of the building is a timber frame? This is really simplifying a lot of my problems. 

[Raider Bill]

No it's ICF walls, insulated concrete forms. Basically, hollow foam blocks you stack then fill with concrete and steel.



 

 

 

 

 

[Brad_bb]

Are you sure your wife is really familiar with timberframing?  Have you walked through some timberframed homes?  Does she know how beautiful timberframe is?  They tend to feel really open!  Timberframes that use too much wood - wood on the ceiling, wood on the walls, etc tend you make things feel smaller.  I like a timberframe with white stained wood on the ceiling, or painted drywall for a light open feel.  


Houzz is a great place to look for design inspirations/pictures.  It's really a great tool to help you guys hone in on what you want to create.  You create your own albums and save the pictures you like.  You can then share the album with your designer or architect.  You can also print the pics so you can sit and talk about them and make notes on them.

I don't know what you mean about moisture coming through the sips.  That doesn't happen.  The purposes of the cold roof are 1. it provides a layer of insulation.  It's a roof on a roof.  The outer roof may get real hot or real cold, but the cold roof airspace keeps your sips from seeing those temps.  2.  Should there be any problem with your outer roof and you get a small water leak, the cold roof lets it run down and out the bottom.  Cooler air is drawn in the bottom as the air space heats up and the hot air goes out at the peak.  This draft will help dry or draw out any moisture.  If for some reason there were any  condensation like in spring or fall, it will draw that out.  3. A cold roof in combination with roof sips will really deaden sound as well.  If it hails, you will barely be able to hear it.  

I would not want to live in a place without a cold roof.

Oh and one thing I forgot to mention, a cold roof makes the outer layer cold in winter so that the snow on your outer roof is not melting and refreezing, creating ice dams.  You can still get ice dams on the south and possibly east sides from the sun, but you shouldn't get any melting from the roof itself.  Your sips roof seals and insulates really well so as not to have heat leaks.  The drafted air in a cold roof also keeps the outer roof cold.  A warm roof from heat leaks is a primary cause of ice dam-ing.  So up north, it's a must.  As I said, it also helps in the south in the summer.

[Brilton85]

Are you sure your wife is really familiar with timberframing?  Have you walked through some timberframed homes?  Does she know how beautiful timberframe is?  They tend to feel really open!  Timberframes that use too much wood - wood on the ceiling, wood on the walls, etc tend you make things feel smaller.  I like a timberframe with white stained wood on the ceiling, or painted drywall for a light open feel.  


Houzz is a great place to look for design inspirations/pictures.  It's really a great tool to help you guys hone in on what you want to create.  You create your own albums and save the pictures you like.  You can then share the album with your designer or architect.  You can also print the pics so you can sit and talk about them and make notes on them.

I don't know what you mean about moisture coming through the sips.  That doesn't happen.  The purposes of the cold roof are 1. it provides a layer of insulation.  It's a roof on a roof.  The outer roof may get real hot or real cold, but the cold roof airspace keeps your sips from seeing those temps.  2.  Should there be any problem with your outer roof and you get a small water leak, the cold roof lets it run down and out the bottom.  Cooler air is drawn in the bottom as the air space heats up and the hot air goes out at the peak.  This draft will help dry or draw out any moisture.  If for some reason there were any  condensation like in spring or fall, it will draw that out.  3. A cold roof in combination with roof sips will really deaden sound as well.  If it hails, you will barely be able to hear it.  

I would not want to live in a place without a cold roof.

Oh and one thing I forgot to mention, a cold roof makes the outer layer cold in winter so that the snow on your outer roof is not melting and refreezing, creating ice dams.  You can still get ice dams on the south and possibly east sides from the sun, but you shouldn't get any melting from the roof itself.  Your sips roof seals and insulates really well so as not to have heat leaks.  The drafted air in a cold roof also keeps the outer roof cold.  A warm roof from heat leaks is a primary cause of ice dam-ing.  So up north, it's a must.  As I said, it also helps in the south in the summer.

She's very familiar with them. She's just not crazy about them. My sticking point is heating it. We are heating with wood and with the floor plan we have in mind, it would be a lot of wasted in the ceiling. That's also the reason we are putting in a basement; for a cold sump to the median air temp on the main floor bearable consistent. But again, my question about a cold roof, is it something I can do and be within code on stick frame trusses in your experience?i want the design to balance my temps as much as possible since we will only have a stove, space heaters here and there and no AC, so the upsides of a cold roof are a no brainer.  Again, I don't HAVE to be within code but for the investment in time and money, I'd like to maximize my investment in terms of zoning and listing as much as possible. 

[Brad_bb]

But again, my question about a cold roof, is it something I can do and be within code on stick frame trusses in your experience?

Code is different everywhere and is dependent on your local conditions and local building requirements.  It's important to become familiar with the codes for your building site.  Codes do not tell you the best way to build, just the minimums they've set.  Often you want to be better than code requires.  

A cold roof, often called a roof on a roof, can be done on any type of construction.  Your insulated and sealed roof can be SIPS, or a stick framed and insulated enclosure. It could also be done over an attic space.  It will keep an attic space from getting too hot.  The farmhouse I currently live in has an attic with no roof insulation.  Instead the floor of the attic is insulated making the attic space the cold space.  The problem with a space like this is the attic gets terribly hot in summer, and any heat that escapes from the floor in winter will slightly heat the roof and can cause snow melting.  This may sound like a good thing, but it can be enough to melt but then conditions outside can refreeze it lower on the roof or in the gutter and rip gutters off when temps outside come up.  This is ice damming.  The point of a cold roof is to create conditions on the bottom side of the roofing that are the same as the top side to prevent ice damming.  It has the added benefit of reducing summer temps.  It's like you're shading your roof with another roof.  Hot air pulls in cooler air from the bottom of the cold roof to keep the temps of the insulated roof cooler.  

I like SIPS on a roof because they seal very well, the insulation is great, there's virtually no thermal bridging, and they are fast to install.  Thermal bridging occurs when heat is conducted through something with low R value.  An example is wood.  If you stick frame the roof, head can be conducted through the wood studs.  In sips that's nearly non-existent.

[ChugiakTinkerer]

Welcome neighbor!  What borough will you be building in?

[Brilton85]

@ChugiakTinkerer we are looking at Anchor Point at the moment. Land in anchorage/matsu is too expensive and I have known too many people from willow in my life for me to want to live up there. 

[Don P]

State building codes are actually quite similar. I think 49 states now use the ICC model codes as a basis and make small modifications.  For the vast majority of things they all stick to the model code. Building codes, that is to say codified (written) law, is about minimums. We jokingly say that a house built to code is as poorly built as the law allows. Generally though it means that if the designer actually understands and follows the intentions, you have a house that has been rationally thought through. Generally speaking and from a lifetime around carpenters, very few people that talk about building codes and say they build to code have ever opened the book. So start there, this is AK, it looks very much like my state code.
=Alaska&page=1]https://codes.iccsafe.org/search/?category[]=Alaska&page=1

Hmm, that isn't getting you quite there, on the left column of that page click category and scroll down to Alaska and click on that.

When someone states that something is required by code, politely ask for a citation, then look it up and read the cited chapter and verse until you understand it. I do not believe there is any mention of what you are describing in the code. Which is to say I know of no prohibition. Chapter 8 of the IRC deals with roof construction, R806 discusses roof ventilation, chapter 9 with roof assemblies.  From there look to best practices for your region and also your roofing products literature. For instance if you were in a wildfire zone this would be an inappropriate roof. More than a few times I've emailed the manufacturers tech assistance line and gotten good advice and a design they will stand behind. I've also had them stop a bad detail from being repeated. I suspect ChugiakTinkerer has some cold weather building resource links bookmarked from his build. buildingscience.com is a good resource I've used. Use vetted resources.

[ChugiakTinkerer]

@Brilton85,

I haven't explored the KPB Planning web site, but their local option zoning looks like a potential minefield if you aren't careful.

There are a couple of folks on the Country Plans forum who have built or are building in the Denali borough.  Depending on what your plans and needs are you might explore that area too.  Go further north and you are dealing with permafrost.  So staying on the Kenai Peninsula might be a good plan.

The Cold Climate Housing Research Center ( http://www.cchrc.org/ ) is mostly focused on housing in permafrost regions but has some innovative building techniques that are applicable throughout Alaska.

The Alaska Housing Finance Corporation also has some best practice information that may help you in building a house that will retain its resale value: https://www.ahfc.us/efficiency/research-information-center/manuals-forms-and-workbooks

[Brilton85]

State building codes are actually quite similar. I think 49 states now use the ICC model codes as a basis and make small modifications.  For the vast majority of things they all stick to the model code. Building codes, that is to say codified (written) law, is about minimums. We jokingly say that a house built to code is as poorly built as the law allows. Generally though it means that if the designer actually understands and follows the intentions, you have a house that has been rationally thought through. Generally speaking and from a lifetime around carpenters, very few people that talk about building codes and say they build to code have ever opened the book. So start there, this is AK, it looks very much like my state code.
=Alaska&page=1]https://codes.iccsafe.org/search/?category[]=Alaska&page=1

Hmm, that isn't getting you quite there, on the left column of that page click category and scroll down to Alaska and click on that.

When someone states that something is required by code, politely ask for a citation, then look it up and read the cited chapter and verse until you understand it. I do not believe there is any mention of what you are describing in the code. Which is to say I know of no prohibition. Chapter 8 of the IRC deals with roof construction, R806 discusses roof ventilation, chapter 9 with roof assemblies.  From there look to best practices for your region and also your roofing products literature. For instance if you were in a wildfire zone this would be an inappropriate roof. More than a few times I've emailed the manufacturers tech assistance line and gotten good advice and a design they will stand behind. I've also had them stop a bad detail from being repeated. I suspect ChugiakTinkerer has some cold weather building resource links bookmarked from his build. buildingscience.com is a good resource I've used. Use vetted resources.

All good points. Thanks for the links. We are ways out come any serious decisions but I like having realistic expectations as well as options. So this all helps.