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Look forward to your build as it progresses. From the pictures it appears that this started in summer/late summer of last year. Can you work at the site now or is it snow covered?
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Is it me, or do your built up beams split between the posts?
Also, may I ask the size of the beams. They look like 3 built up 2x8's spanning a 10 ft? span. I am only going off of this because the beams look as tall as the posts are wide. Also you said it was a 34ft long, and I only see four posts.
Also the center posts look they are poured at ground level and the side posts are sunk below the frost depth?
I'm sorry if I'm misinterpreting any of this, but I'm trying to get a bearing from the pictures.
BTW w*
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I'm a little surprised that John's plans called for this.
Normally the conventional wisdom that I have learned from people on this site is that all joints on beams should split above a post. They become much weaker if not. I have seen this in real world situations were a beam breaks and collapses.
Also the girder sizing for a 10 ft span seams dangerously undersized. A 3ft 6 in. frost line is close to what I am dealing with in upstate NY, so I use the NY state building codes for girder/header sizing. I found them here:
http://publicecodes.citation.com/st/ny/st/b400v07/st_ny_st_b400v07_5_sec002_par013.htm
The maximum span for 3-2x8's is 6ft 5in. for a girder with a center bearing floor at 50lb snow load. I am using 50lbs, because that is what it is in my location with a similar frost depth. If you don't get much snow, you could probably go with 30lbs. That is without a break in the beam. Because you are adding a loft I would calculate it at 2 center bearing floors to be on the safe side with load, but that is just me. Technically, at that load 4-2x12's don't even seem to be rated to span 10 ft. I would add more posts.
Also with the center posts, I believe the fact that the side ones are sunk below the frost line, this could create a problem if they are not and there is frost. Even a few inches shift can easily crack mortar and drywall. I have had to fix this in many houses.
I am a not an expert myself. I have just had to fix certain problems over the years. Someone with more experience can easily jump in and correct any of my suggestions.
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Hi Charlie A,
I like the pictures!
I do however have a question,
what is you spacing between piers?
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Quote from: astidham on February 07, 2011, 05:13:38 PM
Hi Charlie A,
I like the pictures!
I do however have a question,
what is you spacing between piers?
I aimed for 10' (This was when I had planned a pole barn mind you). After digging there were rocks so big I did not attempt to remove them. So I believe the spacing between one set of piers is about 11'.
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I know it is a little late for adding more piers to your build,
You might consider making PTWF panels, and putting them between your existing piers.
below is a link example of what Im talking about.
http://countryplans.com/smf/index.php?topic=4640.0 (http://countryplans.com/smf/index.php?topic=4640.0)
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I see there has been some more added here since I started this post. I'll read it all later. For now...
That's a big undertaking for a solo build. It is very satisfying to look back and see what you've accomplished though. I've been lucky in haveing some help from our son on some of the parts of our build, not to forget my wife.
I like those five foot deep piers. They should not frost heave. They do remind me of the deep holes I dug back home in Manitoba when I was much younger. They also serve as a reminder to myself to not complain this summer when our plans call for digging some more pier holes here. At only three feet I should remember to not complain so much.
I sometimes tend to get wordy so please bear with me.
Not that it will help with this project, but perhaps some reader may benefit. I've built similar pier and girder foundations and have found assembling the girder 2x's right on the piers to work well. Some bar clamps help. It eliminates the task of having to move the very heavy girder as a one piece unit.
I'm guessing that you scaled this up from the Little House plans. There are some concerns when doing that. Squirl addressed some. Here are my concerns and ideas.
It is not clear whether or not the piers for the center girder are also dug down below frost level. They do appear to be at ground level. This might be of future concern as there may be differential frost movement between the deep piers and the surface blocks.
I'm guessing a little now. With an overall length 34 feet there appears to be maybe a one foot overhang at each end of the beam, sometimes called a girder. I prefer the term girder for beams that hold up structures. That would place the piers at ten feet apart, more or less.
As Squirl pondered, that is a long span for a triple 2x8 built up girder. Squirl referenced the NY state building code. It is based on the IRC by the looks of it. Many states use it and may make adjustments in some detailing but basically the structural portions are valid almost everywhere. I do not know what Canadian codes are based on but they are likely similar as this part of the codes are based more on structural engineering rather than being influenced by companies who want to see their products used. For reference anyone can view codes in a few places on the internet. They are normally available at any good public library. Click HERE (http://countryplans.com/smf/index.php?topic=6224.msg81129#msg81129) for an online source. There is likely some Canadian specific site but I am not aware of where right off hand.
The tables in section 5 pertain to floors. Table 502.5(1) is for sizing girders and headers. A one story structure with a loft will have more load on the girders than a structure with no load, but less than a two story. I'm sort of like Squirl in that I tend to be a conservative designer and would lean more towards the 2 story sizing than the one story.
Using the 50 lb.sq ft snow load from where I used to live the one story floor with center support indicates that piers for a girder made from three 2x8's should be spaced no more than 6'5" apart, just as Squirl stated. The two floor with center supports section indicates a maximum span of 5'9". So I believe it would be highly advisable to install more piers in between the existing piers; all with the deep footers.
However, I believe there is another area of concern and I'm not certain how best to handle it. The outboard ends of the floor joists appear to be cantilevered about 2 feet, much like the Little House plans. The big difference here is that the Little House ios designed using one piece joists, no joints in the center. With a cantilever of around two feet there will be uplift forces on those joist hangers. I'm not sure how they will perform in that mode. Best practice here would have been to place the girders directly under the side walls. Maximum cantilever without engineering is limited to the the depth of the joist. That is a 2x8, actually 7 ¼ inches deep, should be cantilevered no more than 7 ¼ inches. A 2x12, would be cantilevered no more than 11 ¼ inches.
I'm not a licensed engineer so maybe there is something I've missed and perhaps this is not as worrisome as it appears to me.
One more point; before getting any further along it would be good to install diagonal bracing between the piers and the girders and joists, in the "north-south" and "east-west" directions.
It looks to me like the joists were trimmed back to be just about the joist depth on the cantilever. Which should be fine.
(https://i1009.photobucket.com/albums/af219/countryplans/cant.jpg)
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Oh that's good. Looking at the first set of photos of the joists themselves and the T&G going down it appeared there was greater overhang. Sorry Charlie, I missed that, but let's leave the commentary as a reminder to anyone else reading. ok?
Sorry I missed on that. :-[ :-[
On the rodent proofing under the floor...
The US National Forest Service has an excellent rodent exclusion manual available online. Link here.
http://countryplans.com/smf/index.php?topic=2919.0 (http://countryplans.com/smf/index.php?topic=2919.0)
Aluminum screen will not keep out rodents. Even small deer mice chew through in no time if they feel like it. It would be better to use something solid like 3/8 CDX plywood or steel hardware cloth with ¼ inch mesh.
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Quote from: Charlie A on February 07, 2011, 08:14:03 PM
I was going to consider ply under the structure but i wanted the batts to breathe if need be. 1/4" steel cloth was a thought,
FWIW, I was concerned about 'breathing' too. We used mostly 3/8 plywood with a strip of the hardware cloth along each side, inboard of the girders.
What is this end? ??? Guest room (they won't stay long) or batteries, or ?
(https://i1101.photobucket.com/albums/g434/CharlieA2011/526.jpg)
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Quote from: MountainDon on February 07, 2011, 08:46:18 PM
What is this end? ??? Guest room (they won't stay long) or batteries, or ?
(https://i1101.photobucket.com/albums/g434/CharlieA2011/526.jpg)
LOL. I was going to stick the kids there when they are bad!
Its going to be a utility room. Batteries/inverter, water heater, electrical panel etc. I didn't want to look at all that stuff.
I thought batteries. I have built a "energy center" on the end of our cabin.
Are you insulating it? I went back and forth between yes and no for a long time.
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Lead acid batteries won't freeze when charged up. I forget the numbers, temperature and % of charge. I have them someplace? Freeze temp on a fully charged battery is very low though.
We use our place every second weekend at most in winter. I leave the charge controller to work its magic all by itself. I do pull the inverter breaker though to fully shut it down. The CC goes through a daily cycle, pumps 200 to 300 hundred KwH of power into the batteries; a brief bulk charge and then most of it in absorb and float. The batteries always check out as fully charged with the temperature corrected specific gravity when we arrive. The winter voltage reads a tad low compared to summer. I fitted more batteries than I would have if there was no winter involved, in order to cover the effective reduced cold weather capacity. Winter here means the occasional drop into the negative F degrees, but more in the 5 to 30 degreesF range. Last week it did drop to -15 F, a new low record at the cabin.
If I was going to be making much more winter use I'd likely insulate to retain the heat that charging and discharging creates. But when it sits there idle for weeks at a time there is very little heat generated. So it didn't seem worthwhile. If the use pattern changes I can change that though.
"At approximately -22 degrees F (-27 C), battery AH capacity drops to 50%. At freezing, capacity is reduced by 20%. Capacity is increased at higher temperatures - at 122 degrees F, battery capacity would be about 12% higher."
" Battery capacity is reduced by 50% at -22 degrees F - but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures - for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever. "
In very cold climates some batteries can be had with more acid, a greater concentration to compensate.
still looking for freeze info....
EDIT: "At a 40% state of charge, electrolyte will freeze if the temperature drops to approximately -16 degrees F. When a battery is fully charged the electrolyte will not freeze until the temperature drops to approximately -92 degrees F."
Charlie: Before your installed the roof metal did you nail steel straps across the peak in place of using collar ties? That's what I did.
Collar ties and rafter ties get confused easily so here's a drawing that explains...
(https://i139.photobucket.com/albums/q305/djmbucket/construction/framing.jpg)
You can still install collar ties but it'll interfere with the cathedral look. ???
The purpose of a collar tie or straps over the peak is to hold things together in times of high winds. The wind flowing over the peak can create lift forces much the same as an aircraft wing. Takes a bit for that to happen, but it can/does.
I also wonder about the two assembled cross beams. A low pitch roof such as yours and mine creates more outward force on the walls than a higher pitch roof. It's not too clear to my old eyes how those are secured to the side walls and rafters. Cross ties like that don't have to be one continuous length but they need to connect securely to the rafter and then the rafter to the wall. Perhaps it is just not clear to me in the photos.
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