NS 16x24 Cabin

Started by ColchesterCabin, May 02, 2012, 05:40:57 PM

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ColchesterCabin

The joist spans for the second floor are 3ply 2x6 no joints. the foundation plans are all multiply 2x8 with staggered joints over pier. Sorry MD yes offset joints I meant to say staggered joints over a pier. Sorry for the confusion long day still tired out from the weekend putting in the piers. 

Hopefully sometime this week or next going to pour concrete 3500 psi  and set up for the May 20th long weekend here in Canada. I have a long weekend from work I may as well take som advantage of the situation and try to get the main floor done or a good start on it done, plus my brother is coming home from Alberta for my Gram's internment, I love to have more to show him for when he gets home. Plus have something lined up for him to do...lol  ;D
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Squirl


I took a look at your floor plan.  Am I correct that the first floor will not have any interior load bearing walls and that the second floor weight will be carried by girders to posts and then directly down to the foundation?  That is perfectly fine, but I am just trying to calculate the load distribution.

I do like the floor plan for the second floor.


ColchesterCabin

Thanks the second floor is supported on one end by the bathroom wall beside the stair case and on the other side by a 3 ply 2x6 over pillar to transfer the weight.... I would be very interested in knowing the math and weight load.

On the set of plans in process with windows and door placements, elevations and such the wood stove would be placed in the L of the stair case with a double lined flue running straight up and out the rook. I figure according to code here I have to go 3 ft above the highest point of the roof within 10 ft. So with only a 16 ft wide floor plan then the peak would be the highest point within 10 ft. I figured better draft with the flu running inside and straight up as opposed to out then cooling the flue as it rised outside the cabin. Plus protruding from the roof within a couple feet of the peak I would only have say 4-5ft of pipe to brace as opposed to upwards of 10 ft of pipe. We get a lot of snow at times up here so with the metal roof less chance of shearing it off with the snow/ice sliding off the roof in the winter. Does that sound like a fair assessment?
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Squirl

Ok, lets start at the roof and work our way down. For estimation purposes.

I will assume a gable roof on the resting on the 24 foot long walls. I read in on source that was not official that halifax has a gound snow load of around 50 pounds per square foot. So I will use that for the math.  I will use 10 psf for materials dead weight.  So you have 384 square ft X 60 pounds per square foot for 23,040 lbs resting on the 24 long walls.  That would be 11,500 lbs per wall.

If you rest the first and second floor weight on the piers and girders for center 16 long walls, then the 11,500 lbs from the roof plus the weight of the walls should be most of the weight for the 24 long girders.  The chart has a table for 50psf and a 20 ft wide building with just the roof and ceiling load.  Even though your building is 16ft wide, I think with the extra weight of the wall materials, I would round up to the 20 ft.  Because your largest span on these girders is 8ft, according the the chart, these girders should be at least 2-2x12s, 3-2x10's or 4-2x8's (it looks like a typo of a 6 instead of a 8 in the chart).

ColchesterCabin

Squirl that's awesome and mad math skills.  By the sounds of it according to the charts I could be a little light. I understand the math now but it seems that it doesn't account for the internal 7'l oad bearing wall or the 3 ply 2x6 beam (6x6 beam) carry the weight over the posts. Morale of the story is not all the weight is distrubuted over the external walls alone. The centre pillars and interanl walls have to be factored in the math, am I not correct?

I don't want to been a stickler I just want to make sure I am not under supporting my structure...
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Squirl

No my math so far was only for the external 24 long walls. 

Because your 2x6 floor joists will be running parallel to the 24 long walls and resting on the 16 ft long girders supported in the center, most of the weight of the first and second floors will not be resting on the 24 ft long wall. In a little while I will try to make some calculations of the load on the 16 ft girders.  They get more complicated.

As you can see from the charts and the math that spans over 6 ft becomes more difficult.  Also a common mistake that I have seen over the years is when people add a lot of center rows of girders, but don't realize that the entire weight of their roof with wind and snow rests on the outside walls.  The way you ran your beams and joists parallel and with center girders cuts down on the weight on the 24 ft long wall.

Squirl

From the code chart you can visualize sizing.  For a 16 ft wide building the beams can span slightly longer than the span listed in the 20ft column in the chart.  For a safety margin and ease of use, I tend just to round up to a 20 ft wide.  If you had run your roof and both floors on the just the outside to span the 8 ft you would need 4-2x12 girders and that would be the maximum distance you could span by code in a 50 lb snow load area. Because you hung your floors from the 16 ft girders, you can get that down to 2-2-12s.

Taller is generally stronger in beams. Notice from the charts 2-2x10s can span longer than 3-2x8s.  It is similar to the principle of I-beams or I-joists. In engineering taller and thinner can be stronger than shorter and fatter.

Additionally you can see why buildings are designed from the top down.  Girder and foundation sizing is dependent upon roof choice, second floor distribution, and first floor distribution.

ColchesterCabin

Well it has been pretty much a solid week of rain here. Around these parts the concrete guys don't pour on the weekends  and with this weekend being Mother's Day, looking like sometime next week before I can get the pillars poured.
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Squirl

Sorry I have been busy with work, I have had time to get the 16 foot girder calcs.
http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_5_sec002_par021.htm

The second floor girders will be supporting 1 floor only (the second floor).  The code has a chart column for a 20 ft wide building.  So the one at the top of your drawing (over the kitchen) will span around 9 ft. This will carry half the load off of each end of the beam, so I will estimate that the beam will carry a floor area of 8 ft x 9 ft or 72 square ft.
Now the code chart has a 20 ft wide column.  Which means the beams will have to hold half the weight (10 ft) times whatever span is listed in the chart.  In the chart 2-2x10s can handle around 70 square ft of floor and 3-2x8s around 72 square ft. 
So for the 9 ft span for the second floor, you would probably be close to code limits with 3-2x8s or 2-2x10s.

I did just notice that the span on the between the posts and the wall is 9', and the spacing on the pier foundation is 7-10" which means you will be resting most of the weight from your second floor on two concentrated spots not over the foundation.  Someone with more experience can let you know if it will be a problem.


ColchesterCabin

Squirl you and MD are the reason I started posting here. I think to solve the problem I just have to adjust the 3ply post to be over the peir. I think that was the intention but I'll check with my guy who planned it out so far... that way the post is over the pillar and the bathroom wall supporting the other half is over one of the center joists  running at the 16' length which should transfer everything equally.

That is an ecellent attention to detail. Have a beer tonight on me  [cool]
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ColchesterCabin

OK, this build is starting to have it's moments....lol Appearently based on the foundation plan posted previously you can not get stock brackets at the local lumber store do what I need them to do to. They have all sorts of 4x4 post to peir connectors, lots of straight support peices for all sorts of 2x lumber, however, what they don't have and can't get it pier brackets for the corners and ones for the intersecting 'T' connections required by the plan.



Luckily I have connections at a Mechanical shop here in town. If I get them the plans by the end of the weekend I should have them designed/engineered and built by Thursday so I can pour my concrete and get the foundation prep work done. Planning on applying some lumber this Saturday and Monday(long weekend here in Canada). A very small set back but I'm sure as I go there will be many more like this... I love this kind of stuff finding creative solutions to solve problems I didn't know exsisted up until last minute...
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ColchesterCabin

Just found out the brackets have been engineered and will be produced and ready for Wednesday now pending a break in the weather,,, looking like a Thursday pour of concrete.
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ColchesterCabin

Thursday May 17th,2012
Well today has been interesting as I sit here and unwind I wonder where the last three weeks have gone. Got to amdmit in three weeks with limited hours we have been able to accomplish alot. Today was concrete day! I feel I have to stop here and smile as I can't believe everything I have learned from both this forum and my building site. Got out to the property at around 9:30 after stopping at the concrete supplier and local lumber yard then a 30 minute drive. Off loaded the 2x8x16' for the outside of the main floor decking. Tomorrow I'll stop back and get the 2x6x8' floor joists and joist hangers. 



I saw a neat trick here on the forum for the concrete once the posts were poured. I took the blade out of my 18V Dewalt Recipricating saw and put it against the tube and pulled the trigger working my way around the tube vibrating the tube to get the air pockets out of the concrete. It even impressed the concrete delivery guy as even he hadn't seen it done that way before...

I decided that between at the bottom of my floor joists I would ripp down 1x3 strapping and nail to the bottom of my 2x6 floor joists then on top of that I am ripping down peg board gluing and and nailing on the outside. i figure the holes will provide ventilation as well as the holes should be small enough to keep critters out. Onto of the pegboard batt insulation, topped with vapour barrier and T&G Plywood for sheeting on top. There will be about at 12" space under the cabin so should have enough breathing ability. There will eventually be skirting around the base of the Cabin with vents.



For those of you here in the forum (MD, Don_P, etc.) does this sound like a workable plan?

P.S. Excuse the MSPaint drawings...lol!
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Redoverfarm

The peg board might not be your best choice.  Mice will whittle out enough to gain entry.  After all it is just pressed paper product.  Your better alternative would be hardware cloth or commonly known as rabbit wire.  Welded wire in 1/4" blocks.

If you are planning on adding the insulation prior to your subfloor you will be taking a big chance that it will get wet prior to drying in your cabin unless you are extremely fast.  Might I suggest at least Advantex which will give better protection than regular T&G subfloor.  Even then there will be some water penetration with your best effort.  Using a latex caulk on the seams will help as well.

If this is the route you are intending to persue you could use the hardware cloth by bending a 1" flange on each side and nailing them onto the inside of the floor joist, then lying your insulation upon that.

Generally the insulation is placed in the joist cavity after the roof is erected to prevent water damage.  But if you can keep it dry your way is OK too.   



ColchesterCabin

Redoverfarm.. I was wondering that which is why I posted about it. As for the insulation the sub floor and is going on the same day as the insulation is going in the joists. I was told that the vapour barrier goes to the warm side which would be right under the sub floor. I have already bought a 24x30 tarp at Canadian Tire today as it was on sale and I intend on wrapping the decking and stapling the tarp down as according to my schedule there will be about a 2 week window to get back to building again. Can I use the stapler to attach the hardware cloth? as that would be convient and simple way of attachment.

I hae never heard of advantex I have to look into that as well.
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Redoverfarm

Not real sure of the availability in NS but it is well worth the extra cost verses regular T&G either ply or OSB.  Here is a site for their product.  Might see a close distributor.  Carried here by Lowes and HD.  There is also a product called Surfloor which is waterproof subfloor as well.

http://www.huberwood.com/main.aspx?pagename=advantechflooring

If you have the room to use a hammer tacker it might work but generally you are limited to 1/2" staple in those as well as T-50 staple guns.  If you can find a crown stapler (air powered) it would work best if you have a compressor.  Another alternative is just 1" roofing nails.

Sorry for the misspelled Advantech. 

MountainDon

Ditto John on the floor insulation going in now being a gamble. I thought of doing that myself on our cabin but changed my mind and as it turned out is was a good thing I did. It got rainy and the heavy plastic, even though new, leaked enough to pass plenty of water. After it was dried in I could see where water had leaked through a few joints in the subflooring. The big advantage to Advantec is that it does not delaminate even if it pours rain for days.

Just FYI, foundation wood (beams) closer than 12 inches to the ground should be PT while floor joists are pgiven 18 inches.

As for the pegboard, it depends on whether or not the rodents are aggressively curious.  :-\
Just because something has been done and has not failed, doesn't mean it is good design.

ColchesterCabin

Thx MountainDon even at 12-18" the 2x material used in my decking is all going to be pressure treated. I can't seem to get a product like Advantech here that i can find right now. I was thinking...Is there something I could paing on the plywood to seal everything up to create the same effect? I was thinking of using a 1/2" pressure treated plywood...
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Redoverfarm

Quote from: ColchesterCabin on May 18, 2012, 05:19:40 AM
Thx MountainDon even at 12-18" the 2x material used in my decking is all going to be pressure treated. I can't seem to get a product like Advantech here that i can find right now. I was thinking...Is there something I could paing on the plywood to seal everything up to create the same effect? I was thinking of using a 1/2" pressure treated plywood...

I would not go with anything less than 3/4" on the subfloor.  Standard for the wall sheeting seems to be 1/2" and 5/8" for the roof sheeting. 

ColchesterCabin

What about an asphalt sealer like for driveways as it will be open for a while the fumes should never be an issue plus when I finish the interior laterit'll be covered over. OR whoudl the chemicals in the selaer react and do more harm then good?
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Redoverfarm

Quote from: ColchesterCabin on May 18, 2012, 06:23:13 AM
What about an asphalt sealer like for driveways as it will be open for a while the fumes should never be an issue plus when I finish the interior laterit'll be covered over. OR whoudl the chemicals in the selaer react and do more harm then good?

Don't think if it were mine I would go that route.  Instead I would caulk the seams, allow to dry then followed by using a good grade of exterior paint as a last resort.  Tarps & plastic will not weather very well if left for an extended period of time.  If you use a tarp/plastic I would tack down a 2X mid center of the floor and stretch the tarp taunt which would give some pitch for the water to drain off the sides/end. 

ColchesterCabin

Now RED that sounds like a great plan that I could manage. Thanks see the simple things one doesn't think of moving a mile a minute... :)
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hhbartlett

Quote from: ColchesterCabin on May 18, 2012, 05:19:40 AM
Thx MountainDon even at 12-18" the 2x material used in my decking is all going to be pressure treated. I can't seem to get a product like Advantech here that i can find right now. I was thinking...Is there something I could paing on the plywood to seal everything up to create the same effect? I was thinking of using a 1/2" pressure treated plywood...

You could use Thompson's Water Seal. Cheap and easy to put on, bonus being your floor will never rot from water leaks in years to come. I think if you use regular T&G plywood subfloor, with water seal, and a big tarp you'll be fine. I know they talk about Avantech on this forum but I've never seen it around here either. I'm guessing there's a premium price for it.

hhbartlett

Quote from: hhbartlett on May 18, 2012, 06:58:23 AM
You could use Thompson's Water Seal. Cheap and easy to put on, bonus being your floor will never rot from water leaks in years to come. I think if you use regular T&G plywood subfloor, with water seal, and a big tarp you'll be fine. I know they talk about Avantech on this forum but I've never seen it around here either. I'm guessing there's a premium price for it.

P.S. Bungee cord the tarp around your piers. Staples won't hold in a wind, but the tarps should have metal eyelets for bungee cord purposes.

hhbartlett

Quote from: Redoverfarm on May 18, 2012, 06:37:00 AM
Don't think if it were mine I would go that route.  Instead I would caulk the seams, allow to dry then followed by using a good grade of exterior paint as a last resort.  Tarps & plastic will not weather very well if left for an extended period of time.  If you use a tarp/plastic I would tack down a 2X mid center of the floor and stretch the tarp taunt which would give some pitch for the water to drain off the sides/end.

Part in bold = great idea.