| . 1 . 2 . >> |
| Author |
Message |
travellerw
Member
|
# Posted: 25 Jul 2021 12:05am
Reply
Ok, I'm looking for input. Purchased some land and will be building a cabin (structure at least) before the snow flies. My wife and I have gone through a bunch of designs and think we finally agree and settled on the design below. 16' wide and 28' long. One thing that will change is the outer walls with be 10ft tall, but the loft floor will remain at the same height to gain some headroom in the loft
Now, here is the problem. My wife DOES NOT want a post running from the ceiling to the floor. She wants the ceiling to be completely open. Collar ties are OK, but otherwise open. So I know that in the loft area, the floor of the loft acts as a rafter, but there is 14ft were there is no loft or rafters. I'm unsure how to engineer that. I was thinking triple 2X10 (or 12) with beams in the gable ends to carry the load down (yes with beams over the windows). However, not sure that is sufficient or I would need a lam beam..
Thoughts?
Cabinfull.png
| 
Cabinmain.png
| 
CabinMain2.png
|  |
|
|
Brettny
Member
|
# Posted: 25 Jul 2021 06:33am
Reply
You dont need to carry any load down on the gabel ends if you use horizontal beams at the top of the walls. If you try to carry the load down at the gabel walls you need to do that over the loft also or move your staircase out of the center of the loft.
Your going to have prety decent headroom by the looks of it in the loft. I originally had my stairs coming up in the center but decided to move then to the side as headroom is prime space in a loft and didnt want to take it up with the entry to the stairs.
|
|
travellerw
Member
|
# Posted: 25 Jul 2021 10:41am - Edited by: travellerw
Reply
Hmm not sure I understand. Are you saying I could use a heavy beam along each of the 28ft walls to prevent push out where there is no loft? The snow loads are a real concern here (3ft is not uncommon).
As to the ladder. It will be movable on a bracket like the one in this picture. It tucks up against the wall and the kitchen cabinet when not in use. Its one of the reasons we will make the walls taller. That will allow it to tuck up tight to the wall.
|
|
Brettny
Member
|
# Posted: 25 Jul 2021 03:07pm
Reply
Sorry no the correct wording is rafter tie. In your situation it would go ontop of the 10ft wall connecting both 10ft walls. I dont believe they need to be every 16in but that depends on what your code allows and what the dimentions of the top plate are.
|
|
travellerw
Member
|
# Posted: 25 Jul 2021 03:54pm
Reply
Quoting: Brettny Sorry no the correct wording is rafter tie. In your situation it would go ontop of the 10ft wall connecting both 10ft walls. I dont believe they need to be every 16in but that depends on what your code allows and what the dimentions of the top plate are.
Sorry I must not have been clear. That is exactly what we are trying to avoid. My wife does not want any rafter ties in the open area. Of course the loft floor becomes rafter ties in that area, but over the other part of the building she doesn't want anything. She also does not want a supporting post running through the middle of things.
|
|
Brettny
Member
|
# Posted: 25 Jul 2021 06:07pm
Reply
You really have no other option than to use a ridge beam then. Unless you can some how use cables and shes ok with that.
|
|
Brettny
Member
|
# Posted: 25 Jul 2021 06:12pm
Reply
Actualy you dont need any support for a scissor truss but would limit head room in the loft.
|
|
ICC
Member
|
# Posted: 25 Jul 2021 06:19pm
Reply
A snow load like that needs rafter ties or a ridge beam or switching to factory made trusses.
Also the loft floor joists as you describe, will not be an approved method under most building codes. That method will place rxtra bending force on the 10 foot wall studes especially with potential high snow loads.
When you see wide open cathedral like ceiling spaces you are often looking at non-engineered construction. Pretty much all the upscale homes magazine examples are engineered with details you cannot see the pictures.
|
|
|
travellerw
Member
|
# Posted: 25 Jul 2021 07:28pm
Reply
Quoting: ICC Also the loft floor joists as you describe, will not be an approved method under most building codes. That method will place rxtra bending force on the 10 foot wall studes especially with potential high snow loads.
Can you explain why you think that? I have an approved plan as long as I do a complete 2nd floor (where the floor joists act as ties). In that design, its 2X6 walls with 2X10 floor joists. The joists are resting on sistered 2X4s glued and screwed to the 2X6, with the 2X10 screwed to the 2X6 as well..... but my wife would like a lofted area in the living room to give it an open feeling. Not sure why that wouldn't be an approved method. The design show we would be over 50#/sf live load (local code is 22#/sf), so we are over double code.
I know I will probably have to get an engineer, but I'm hoping to get some thoughts and insights before I go that route. I appreciate any responses.
|
|
travellerw
Member
|
# Posted: 25 Jul 2021 07:44pm
Reply
Quoting: Brettny You really have no other option than to use a ridge beam then. Unless you can some how use cables and shes ok with that.
This is exactly the type of comment I was looking for. My wife really likes that idea. We have some 316 stainless cables that are from a sailboat we lived on for 5 years. It would be really cool to incorporate that into our cabin. I gotta go do some thinking about that now!
|
|
ICC
Member
|
# Posted: 25 Jul 2021 10:24pm
Reply
I may be at a disadvantage here as I see you are in Canada. I live in the US and have been involved in construction here in the western US for a long time. But the rules can be different in Canada.
If I understand what you are proposing, the walls will be framed with 10 foot tall 2x6's. The loft floor will be placed at a height of 8 feet. That will leave a 2 foot stub of wall above the loft floor joists.
A gable roof is a very strong roof when it is built built with the rafter ties forming a triangle with the pair of rafters. The lower chord, the rafter tie. is also tied (nailed) to the top plates of the long side walls, restraining the wall tops in place. Without a rafter tie for each pair of rafters, nothing restrains the wall tops from spreading outwards. The walls where the lof is located would be restrained by the loft floor joists which are lower in the wall. Those stubs of wall studs sticking up are not meant to have lateral forces applied to them.
We (my brother's licensed contracting firm and I) have worked with a few professional engineers over the decades. This question of a "dropped loft floor" design comes up constantly. I have asked many of those engineers if this is good practice. None, not one, has ever stated it was good design when asked. They would not sign off plans to be built this way because it is not a structurally sound design.
US building codes specifically state that each rafter pair must have a rafter tie located across the wall top plates and connected to the rafters in accordance with a nailing schedule. Things could be different in Canada; I do not know.
FYI, IF the snow load was 45 PSF, my calculator shows that each rafter would exert a 360 lb horizontal force where it attaches to the wall top. That is calculated on a 16 ft wide bldg with a 12/12 pitch roof and rafters spaced 24" apart. If the roof is steeper the lateral load is reduced; build a 6/12 pitch roof and the lateral load will double, compared to a 12/12. Where I am. snow can vary from light, dry powder to wet and sticky. Three feet of the wet sticky stuff produces a load greater than 45 PSF.
You mentioned "an approved plan as long as I do a complete 2nd floor (where the floor joists act as ties)."
You are modifying it and that negates the approval. So, yes. you should get an engineer involved, especially if there are inspections and permits involved. If this is in an area with lax enforcement you could build whatever you want, but it might not be a safe structure.
You also mentioned the use of screws. Screws are not usually used by engineers or architects in structural design unless they are specifying a particular structurally rated screw that has been approved. Is this the case? If so, I trust the design if done by and stamped by a licensed professional engineer. If a DIY design, I remain a cautious skeptic. But then , that is my nature.
Cables or steel rods can be and have been used for restraining wall framing. We did remedial work on an old church here many years ago. The open cathedral ceiling looked great, but the walls were spreading. An engineer designed steel rods to span the width. One of the elements of that design was to have properly sized steel plates to spread the load out on the walls. Incorrectly sized anchors could have traded the old problem for a new one. Hire an engineer when stepping outside the conventional and proven methods.
Rafters with a ridge beam removes the side wall horizontal loads and transfers 50% of the total roof load to the gable ends supports. That would need a beam to be sized for the snow load and proper support columns in the gable end walls with appropriately sized foundation supports.
An alternate to rafters would be trusses. There are trusses that are sometimes called attic trusses. They could be used for the loft and an engineered series of beams, or rods or cables used across the open area. Attic trusses are somewhat limiting to the width of the loft floor usable space.
|
|
ICC
Member
|
# Posted: 25 Jul 2021 10:25pm
Reply
Just a head ups re the posted image. It is so large that it can make it difficult to read this thread on a small screen device.
|
|
jsahara24
Member
|
# Posted: 26 Jul 2021 09:01am
Reply
Have you looked into Scissor trusses?
|
|
snobdds
Member
|
# Posted: 26 Jul 2021 10:40am - Edited by: snobdds
Reply
deleted...
|
|
Grizzlyman
Member
|
# Posted: 26 Jul 2021 09:32pm - Edited by: Grizzlyman
Reply
I just finished a similar build with 10’ walls , and loft over half- similar to yours. Mine was 22’ wide by 20 long. Just finished weeks ago.
My wife also did not want rafter ties. I told her jokingly “sorry, blame physics†with the understanding that it is necessary.
After “seeing it†and having several 70lb 14’ 2x8 rafters hanging above my head as I hauled another one 16’ in the air on a step ladder….and then seeing how much more solid they become with the rafter ties added and blocking it became obvious that it was necessary.
That, and it looks fantastic with the rafter ties. Seriously - it looks almost better with them than without. I used 22’ 2x8s for rafter ties and love the look. That and since they were 10’ up they’re well above you… my wife even agreed she was worried that they’d be hanging close to you but that’s not the case with the 10’ walls.
Also- for what it’s worth- and I’m 100% serious here- I built 10’ walls and though it does look great if I did it again I would 100% just do 8’ walls. Frankly- IMHO it wasn’t worth it. With the loft and the cathedral ceilings the extra wall height was really not necessary. It kind of gets lost in the cathedral as opposed to adding to it- just my opinion having been in it now.
As far as the work required for 10’ walls:it doesn’t just add 25% more complexity- it’s about 50-75% more complexity when you start to figure that you can’t reach the top with a hammer anymore, and are 2’ higher on a ladder, or have to lift OSB 2’ higher, need more sheets of osb, gable walls are now 16’ balloon frames instead of 14, roof ridge board in my case was now 16’ in the air instead of 14’, walls are heavier, etc, etc, etc… I overcame all these challenges just fine- but frankly wasn’t worth the added effort. Just my .02!
|
|
gcrank1
Member
|
# Posted: 26 Jul 2021 10:07pm
Reply
So, if Im envisioning the ties right....it is kind of a pergola effect?
|
|
Brettny
Member
|
# Posted: 27 Jul 2021 05:46am
Reply
If you want loft head room and 8ft walls you can do a gambrel roof. It will ad a bit of complexity to the roof framing but your also not working on a very steep roof on half of it. Working on the nearly vertical section of the roof you can stand on the top plate or work on a ladder. It's way easier to work on over say even a 6/12 pitch where you need to be tied on. Even a 4/12 metal roof you slide off.
|
|
Grizzlyman
Member
|
# Posted: 27 Jul 2021 10:05am
Reply
Also- not to beat a dead horse here…. But if I understand your plans you’re putting a loft on top of 10’ walls. That means that by the time you account for the 2x10s and plywood your loft will be 11’ off the main floor… that’s really high.
Lastly what is going to be supporting the loft in the open section above the kitchen? That’s a 16’ unsupported span. I believe that would necessitate a 12x2 floor unless buying very specific grade 2x10s… but I’m not a lumber expert!
Just trying to be helpful!!
|
|
snobdds
Member
|
# Posted: 27 Jul 2021 10:36am
Reply
Quoting: Grizzlyman Also- for what it’s worth- and I’m 100% serious here- I built 10’ walls and though it does look great if I did it again I would 100% just do 8’ walls. Frankly- IMHO it wasn’t worth it. With the loft and the cathedral ceilings the extra wall height was really not necessary. It kind of gets lost in the cathedral as opposed to adding to it- just my opinion having been in it now.
See I think it was worth the hassle of building tall walls to get the biggest benefit of a loft. I went with 12 foot walls and have the loft at 8 feet, giving me 4 feet of knee wall before the roof, which is 10/12. It's as roomy as any full sized room. I didn't have a lot of room to build out, so I went up.
As far as rafter ties goes, I didn't want any in my main room. I had to have an engineer and architect get creative with the rafter ties, but having an open area next to the loft is awesome. We put them on the outside of the main building that tied into roof and overhangs. It was a real challenge to build, but it's a very usable cabin with not much wasted space. Plus it holds up to 20 feet of snow every winter, so it's really strong too.
|
|
NorthRick
Member
|
# Posted: 27 Jul 2021 05:14pm
Reply
Quoting: travellerw This is exactly the type of comment I was looking for. My wife really likes that idea. We have some 316 stainless cables that are from a sailboat we lived on for 5 years. It would be really cool to incorporate that into our cabin. I gotta go do some thinking about that now!
That's what I was going to suggest. Steel cables or rods across the open area at the tops of the walls.
|
|
gcrank1
Member
|
# Posted: 27 Jul 2021 06:01pm
Reply
We dont have a loft, and do have 2 central ridge support posts and some rafter ties for the not so many metal roof rafters (with perlins for the metal).
And I have added some 'interior perlins(?)' between those rafter ties that are not attached, that is, I can move them about to hang stuff from, like our self contained 'Edison bulb' look LED lights to have light right where we want it. Point is, it is really nice to be able to hang stuff, useful and/or fun and interesting, from crosswise pieces above.
|
|
travellerw
Member
|
# Posted: 27 Jul 2021 10:32pm
Reply
Holy crap.. I love the comments and they have given me a ton to think about. I will respond to a few before thinking though.
1. I have looked into Gambrel and am still on the fence. The one truss place I called said they would not build them if it was for human habitation. Plus, I'm pretty sure they still need rafter ties as they are a rafter system. A cool look and added space in the loft, but complex and not sure if they are actually certified for human buildings up here.
2. The plan was to build 10ft walls but put the loft at the 8ft mark, so it won't be that high. Still on the fence about this as research shows some engineers are reluctant to sign off on that design. However, I do have an engineered design with a full second floor designed like that.. So it seems its not a cut and dried argument (Grisslyman's picture looks like its built like this as well).
3. A 2X10 can span 16ft unsupported. It will actually be shorter due to the 2x6 wall construction.
4. I really have to rethink the the rafter ties based on Grizzlyman's photo. They really don't look that bad, and could be usefull for hanging lights. However, I'm not sure how they would look if you drywalled the roof above them and left passing through the drywall. Someone correct me if I'm wrong, but I think they could even be installed higher as code allows them to be 1/3 up the rafter?
Now some background. The property is located in a very rural county that really has no rules about "agriculture" buildings. Since the land is considered undeveloped farm land, its pretty much open game. However, with the cost of building things nowadays, I really don't want to gamble and am doing what I can to meet standard urban codes. That said, I am building it on a floating foundation as there is no way to get equipment there feasibly. Not to mention the frost line is like 10ft so a hoe would be required. Possible, probably, practical, no.
8ft walls with a gambrel roof and rafter ties 1/3 up over the open section seems like it might fit the bill. Except for the "human habitation thing" (plus I think it would really suck to put roofing material on that). I guess I have more research to do.
|
|
travellerw
Member
|
# Posted: 27 Jul 2021 11:10pm
Reply
Ok.. One last thing after a little thinking..
A Gambrel roof seems like a HUGE waste of very expensive sheeting for a 16ft building. Since the walls will technically be 16'3" that would put the dimensions of the roof at 6' 2 5/8".. Meaning I would be throwing away almost 1/2 a sheet of sheeting for every second sheet.
Am I missing something?
|
|
Brettny
Member
|
# Posted: 28 Jul 2021 06:17am
Reply
I havent used the gambrel calculator for a 16ft wide building but you wouldnt throw out what's left of a sheet. You would use it on the next roof section. Also if you need certified plans I suggest you start by talking to an engineer that can build and stamp plans for you. All the brain storming in the world wont help if you need rafter ties for the tall ceiling to work.
|
|
travellerw
Member
|
# Posted: 28 Jul 2021 03:38pm
Reply
Quoting: Brettny I havent used the gambrel calculator for a 16ft wide building but you wouldnt throw out what's left of a sheet. You would use it on the next roof section.
It would leave me with a piece that is like 21 inches high. If you used it on the next roof section you would have an unfinished section of like 5 inches. Even playing around with slopes, it doesn't change the measurements much (like 1-2 inches depending). Not good practice to fit little pieces like that on a roof (at least to me). So I'm left with all those 21 inch pieces which I could use for gussets, but there is more material than gussets.
Anyway.. I will be talking with an engineer, but I would like to have my own drawings to give to him. Of course he will redraft it, but it will give him something to work off of!
|
|
NorthRick
Member
|
# Posted: 29 Jul 2021 04:06pm - Edited by: NorthRick
Reply
If it were me, I'd stick closer to your original plan: 10-foot 2x6 studs with the loft at 8 feet and let-in a board for the loft joists to sit on. Install a regular roof and don't mess with gambrel.
That's sort of what I have going on. Except my loft joist run the long way (16') and are on joist hangers. I also have a center post supporting the loft and the ridge beam. Also, I went with 12' studs for more room in the loft.
|
|
WILL1E
Moderator
|
# Posted: 30 Jul 2021 08:58am
Reply
NorthRick gotta love them Xtratufs!! I get weird looks when i wear mine around here in WI. Another reason i need to move to Alaska so i fit in better 
I'm in the same boat as travellerw, but i like NorthRick's idea of doing 12' walls and a gable roof!
Quoting: NorthRick Except my loft joist run the long way (16') and are on joist hangers.
What was the deciding factor for you to do this way? Just curious, not criticizing.
|
|
NorthRick
Member
|
# Posted: 30 Jul 2021 12:42pm
Reply
Quoting: WILL1E What was the deciding factor for you to do this way? Just curious, not criticizing.
Shorter distance. The cabin is 20' wide and 32' long. The loft is half the distance of the long dimension, so 16'. If I ran the joists the other way, they'd be 20' long.
The roof is supported by a ridge beam (a big glulam beam) and so I don't have the issue of the rafters trying to spread the walls out.
|
|
WILL1E
Moderator
|
# Posted: 30 Jul 2021 01:08pm
Reply
Got it!
|
|
travellerw
Member
|
# Posted: 4 Aug 2021 05:18pm
Reply
Ok.. after some thinking and more thinking.. I'm still undecided..
I have been thinking about a Gambrel roof and I like the idea (as does my wife). However, it dawned on me that I have no idea how I would vent that! I'm thinking I would use 2X8s instead of 2X6 and do a 2" overhang over the top plate for a thin soffit. Then use baffles that ran up to a top ridge vent. R21 insulation with vapor barrier on the on the underside of the rafters. Sound feasible?
|
|
| . 1 . 2 . >> |
