10x12 "D log" cabin - Small Cabin Forum (3)

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Small Cabin Forum / Member's Projects and Photos / 10x12 "D log" cabin

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w8n4rut Member	# Posted: 30 Sep 2014 07:44am Reply Quoting: Mainiac By the way.All that cantilever stuff will rot away in a few years.All those ends sticking out and his porch supports-deck in front will rot away too.On the sides the cabin rests on that. I do agree with you on this also.

JBruinsma Member	# Posted: 30 Sep 2014 01:44pm - Edited by: JBruinsma Reply W8n4rut - thanks for the encouragement! Please understand that the "shed", as I now would like to call it, is a work in progress. Initially I was going to have a shed roof coming off the main roof to cover the side porch. I have considered cutting those logs flush with the cabin walls also to avoid the pain of figuring a way to keep the water and snow from sitting on the timbers. I am also continually trying to excavate by hand the area around the front of the cabin so I minimally have 18" of clearance to any non treated wood. If this is accomplished do you still think I will have rotting issues. All logs and timbers will be treated once I get time to strip the bark off. The snow up here isn't what you may expect. We do have a occasional storm that could drop 3 feet of snow but it usually melts quick. I would say the average amount of snow sitting on the ground during winter is only 4-10".

skootamattaschmidty Member	# Posted: 30 Sep 2014 03:08pm Reply As long as you can keep the wood dry you wont have a problem. If it continually gets wet from rain, snow etc and cannot dry out, then you will have rotting issues.

bldginsp Member	# Posted: 30 Sep 2014 03:11pm Reply Building the main girders out of two 2xs is itself a problem for water retention, since any water that gets between the two is held in place without drainage or venting.

JBruinsma Member	# Posted: 30 Sep 2014 08:48pm Reply I do agree with most of what is being said about rotting and log type building are definetly more maintanance. That being said, there are plenty of 100 plus year old cabins that are still standing. Not that they are in great shape but they don't just rot away in a couple years. As a matter of fact there is the original homestead cabin that still exist about 1/2 mile from my property. It is 100 plus yrs old, sits on a stacked rock foundation, and appears to have original logs. It is still being used for recreation even. There is some rot in the bottom logs but you would be surprised what good shape it's in. These things last longer than one would think.

skootamattaschmidty Member	# Posted: 30 Sep 2014 09:16pm Reply My cabin was built in 1978 and is a log cabin. The roof overhangs at the sides by two feet and the porch is covered by the roof. It shows absolutely no signs of rot or decay. As long as the logs are kept dry you are fine. If they are allowed to get wet and they can't dry out then you will have issues. There are tons of log cabins out there that are 100 plus years old. Do not get discouraged by what others say. If the logs don't get wet you will be fine from rot.

bldginsp Member	# Posted: 30 Sep 2014 09:21pm - Edited by: bldginsp Reply The oldest building in Plumas County, California is a log cabin built by Jim Beckwourth about 1850. It's still in good shape. It has, now, a rubble stone foundation that holds the lowest logs a good 2 feet off the ground. 164 years isn't bad, but there are wood frame structures in Europe over 1000 years old. Oldest log cabin in the US is in New Jersey, built by Finns in 1640. 374 years isn't bad. But Bruinsma's won't last that long unless he does something with his foundation, which he seems to be leaning toward. Hope the bldg dept is sympathetic.

timcook Member	# Posted: 30 Sep 2014 11:41pm Reply Nice work the cabin looks really good, love the setting

w8n4rut Member	# Posted: 1 Oct 2014 06:50am Reply Quoting: bldginsp But Bruinsma's won't last that long unless he does something with his foundation, which he seems to be leaning toward. Hope the bldg dept is sympathetic. bldginsp- I'm just curious what you think the issues with the foundation are... The "girders" look to be 2 12"-microlams at the most spanning 7'-8'. Even with any loads not being directly on the piers it will not have any problem carrying that. I don't see any bearing/weight issues. Lateral movement with some of piers being so far out of the ground I could see...except for the fact that on the uphill side the micros are sitting right on the ground bracketed to the piers. Assuming that the piers are deep enough and the joists are fastened properly to the girders I don't see lateral movement being a problem either. I do see water issues. Girders don't look to be treated. The uphill side girder sitting right on the ground is definite problems down the road along with cantilevered floor joists and bearing posts on front porch. If this does end up getting run through the zoning/building department and is inspected those will not pass. Not trying to cause arguments....just always looking to learn w8n4rut

bldginsp Member	# Posted: 1 Oct 2014 07:36am Reply I think it will hold up for quite a while, particularly if carefully maintained. But the girders on the low side will get more moisture and go first. It's definitely not a long term foundation that will outlast what is above it. As far as the piers and support of the building, I'd be interested to see a basic engineering analysis including snow loads (which he says are not what you might think). But piers really don't work well for significant lateral loads. But maybe a 120 sf building wont get significant lateral loads. The longest lasting buildings keep the wood very high off the ground. Anything else is doomed on the long term, but maybe Bruinsma doesn't want a building that will outlast his grandchildren. I tend to go to the extreme with longevity, but maybe I shouldn't impose my beliefs on others. I also think that if someone doesn't want to build a 'permanent' building they have the right to. To each his own.

w8n4rut Member	# Posted: 1 Oct 2014 07:54am Reply Thanks bldingsp- I agree with you on the water moisture issues. It is the demise of many structures. If built with treated material I don't see any problem with the structure. It is only a 10'x12' building. Just curious- from your handle you are a building inspector? w8n4rut

bldginsp Member	# Posted: 1 Oct 2014 08:10am - Edited by: bldginsp Reply Yes, I'm an inspector in a city in the San Francisco Bay Area. Treated wood isn't permanent wood- it just delays the inevitable, where there is significant exposure to water. And I agree that for 120 sf buildings, maybe we shouldn't make a fuss. Its just that Bruinsma went to such an effort with a nice structure above, it seems a shame to put it on a foundation that won't last as long. But there I go imposing my opinions again.

Mainiac Member	# Posted: 1 Oct 2014 08:34am Reply You cant really impose SF stds on a 10 by 12 cabin. As for log cabin longevity,I would give his 20-30 years.I have no idea if that foundation ,yes its not to the local code,is a huge issue.Other than its just not to code. Maybe those old cabins were built with rot proof woods?Without splash back the bottom logs will last longer. My wifes ancestral home is still in use and was built in 1680 or so.The original one room part is P and B,hewn white oak.Its not to code either. All we want to do is get him enjoying his cabin without him getting flagged by the BI.

w8n4rut Member	# Posted: 1 Oct 2014 08:46am Reply Quoting: bldginsp Treated wood isn't permanent wood- it just delays the inevitable, where there is significant exposure to water. I agree...where there is significant exposure to water. Water is your enemy without a doubt. JBruinsma- not trying to hijack your thread! Please keep us updated on your build and how things pan out with the local powers to be....

bldginsp Member	# Posted: 1 Oct 2014 08:50am - Edited by: bldginsp Reply 'SF standards' are no different from Colorado standards, its the same building code, different region, different uses. Sometimes rural jurisdictions are more strict with the same building code. He already is flagged by the BI. We still don't know how they are going to look at it. Hopefully, they call it a 120sf utility accessory structure, and leave him alone. If they call it a dwelling, that's a whole different ball of wax. If they call it a utility building and leave him alone, he can choose what he wants, and we arm chair pundits can spout all we want. In the city where I am, we'd call it utility so long as it has no plumbing. We have left alone many backyard buildings like this because the building code tells us we have no jurisdiction, and we don't want to mess with it. The 120sf rule makes it easier for us and the owners. I hope that's what happens in this case, but often rural jurisdictions impose a higher standard in cases like this for the simple reason that they have so many such buildings and its obvious that they will be used for dwelling purposes. In the city, in the back yard of a house, its less likely that it will be used for dwelling if it has no plumbing. There's a bathroom 30 feet away in the house, so why put one in the backyard playhouse/office/storage shed? On a remote rural parcel, where its the only building, what's going to happen in that structure? Kind of obvious. There was one house here in our city where the owners put in three 120sf total rattrap 'sheds' in their backyard, as 'art studios'. They were far enough from the fence, so we left it alone. I really doubt that a rural jurisdiction would look at three 120sf buildings without any concern for them being used as dwellings. Different area, different uses, same building code, different interpretations.

JBruinsma Member	# Posted: 1 Oct 2014 02:28pm Reply The girders are indeed PT lumber. The Lowes' around here don't sell the nasty green PT lumber anymore. I am not sure of the specifics but the PT they sell is redish in color. No worries on a thread hijack! The back and forth is one of the reason I posted originally. I am no expert in any of the building process'. I simply had a dream of owning true mountain property and with my young family I need somewhere to get out of the weather if need be. I thought it would mean more to us if I built the shed vs paying someone to do so or even stick framing something. The shed has become something I hope the family can be proud of and I do want it to b around for a long while. Thanks for everyone's continued help, suggestions, and even the negative stuff can be productive sometimes. In the end, whether I need permits and a engineered foundation or not, I hope the shed will be a safe and structurally sound place to assist us in enjoying our property for years to come.

bldginsp Member	# Posted: 1 Oct 2014 02:34pm Reply Keep us posted Bruinsma. I'm curious to know how your local bldg dept handles it. And once again, very nice cabin. I'm sure it will be a source of family pride and pleasure for years to come.

JBruinsma Member	# Posted: 1 Oct 2014 02:47pm Reply bldginsp- Do you think I need rafter ties! The roof is obviously a ridge board type roof. I know now I may have been better off with a ridge beam style. The board is a true 3"x12+" as the bottom edge is natural so it varies a bit. The rafters are all true 2"x10" minimum. Some of the are closer to 2x12 as they also have a natural edge. They have birds mouths and hurricane ties. They are all fastened on each end using 16d nails.

bldginsp Member	# Posted: 1 Oct 2014 03:04pm Reply Maniac- California, Colorado, and Maine all use building codes based upon the International Building Code (IBC). I don't know whether all municipalities in Maine have adopted the Maine Building Code or not, perhaps some have not. The IBC is what is used in most parts of the country now as the basis of the building code, with local alterations. But it doesn't matter too much exactly which code is being used for the issue we are dealing with here, because all the building codes that have been used all do the same basic thing with respect to dwelling requirements. They provide minimum safety/health/sanitation/heating/ventilation etc requirements so that sleazy developers can't sell dangerous housing to unsuspecting families. The idea is to prevent the awful substandard housing that existed 100 plus years ago. So if its a residence it has to have the minimum requirements. But small cabin builders are not sleazy developers trying to foist garbage on unsuspecting innocents. They are recreational campers. Should they be held to the same standards as new permanent houses? Every building department has to draw the line somehow, allowing recreational uses for folks like us while preventing the abuses that would occur if not prevented in regular housing. This is true in remote rural areas just as much as in large cities. The county that I am building my cabin in is one of the lowest population counties in all of California, but the building department is more strict there on some things than we are in the city, because of snow loads and because there are a lot of failing septic systems there (and statewide). There aren't different standards in rural areas, because human life is worth the same there as it is in downtown San Francisco (though some might argue the reverse...) So when a building inspector sees a cabin like Bruinsma's, he sees the potential for injury to people, and he sees a simple recreational cabin that won't get used much and probably doesn't pose much of a threat. His department will have to make up their mind if they want to call it a storage shed and risk someone getting hurt, or call it a dwelling and make the owner over-build it to the point that it probably can't hurt anybody. Each department handles that differently according to their thinking and what they know the local voters want them to do.

bldginsp Member	# Posted: 1 Oct 2014 03:09pm - Edited by: bldginsp Reply Bruinsma- absolutely yes. I'm surprised the engineers on this site haven't piped up yet, perhaps they will. A ridge board type roof has absolutely nothing to prevent the two roof planes splaying out when weight is applied, unless the rafters are tied together somehow. You must have three sides to the triangle. The ridge board is barely even a structural element, it is not a beam and provides no support. I recall from your previous photos that the ceiling joists had no solid connection to the rafters. A good snow could cause collapse if there is no such connection. Regardless of all else, get that done before the snow comes. It looked to me like the joists were attached to the walls with joist hangers, so the pullout strength of the hanger nails will be resisting the loads imposed on the roof. Not good, even in a small building like this. Looking at the pics again it looks like there are no ceiling joists over a large portion of the building. I think that is not good. You could put in a ridge beam, but the board in place now is not large enough and the ends of the beam must have piers under them supported by posts. The issue of your rafter span is a separate issue, I bet they are fine, particularly at that pitch, but you should do calcs. Still that is separate from making the triangle secure.

JBruinsma Member	# Posted: 1 Oct 2014 03:31pm Reply Pardon my ignorance but I am calling the beams from the ridge board to the walls rafters. What are you calling ceiling joists when you state " the ceiling joists had no solid connection to rafters."? Do I need rafter ties on all rafters? They are on 2 ft centers. What size lumber would u suggest? Rafter ties need be in the bottom 1/3 of rafters correct? Thanks

bldginsp Member	# Posted: 1 Oct 2014 03:38pm - Edited by: bldginsp Reply Ceiling joists are horizontal members. One of your photos shows one at the entry to the loft. I think you have no others. Yes rafters are the angled members from the ridge down to the wall top. Stretch 2x6s between the rafter bottoms every four feet, on top of the wall, with the face of the 2x6 against the face of the rafter on both sides, and connect the two with, at least, 5 or 6 #16 nails on each side, or use several 3/8" bolts on each side, or 4 or 5 SDS screws (special structural screws) Properly, I think, a rafter tie is on the top of the wall attached to the bottom of the rafters. A collar tie is higher up along the rafter. The higher it is placed the less effective it is because you have a smaller triangle. Since you are dealing with snow loads you want the stronger option, as I described above. But I should say that I'm winging it here, these are all educated guesses not engineered calculations. If your cabin was not subject to snow loads it would be less an issue since its so small, but you could easily get two tons of snow on that little roof and its not designed for that now.

JBruinsma Member	# Posted: 1 Oct 2014 10:20pm Reply No glue lam used. If you are referring to the girders the cabin is built on they are 2 2x12's pressure treated and screwed together. They are bolted together also at the brackets coming out of the cement piers. I will be adding a 3rd 2x12 when time permits. That will mean the shed will be sitting on 2 beams that are 4.5x12. I guess I could add a 4th if needed? Bldginsp There is currently no ceiling joists. I think what you saw in one of the pictures was just a beam we where using to get across the roof b4 it was finished. That beam is now gone. I don't think my loft joists are acting as rafters ties as they are currently fastened to the wall just below the rafters with joist hangers.

bldginsp Member	# Posted: 1 Oct 2014 10:35pm - Edited by: bldginsp Reply That's what I thought. Again, with such a small building it probably wouldn't matter if there was no snow load. Your ridge board will function as a ridge beam in light loads, but not snow loads. I think you need support in case of a heavy snow that doesn't fall off the roof right away. Even with a steep pitch roof sometimes the snow sticks for a while. What you have is a 5 sided polygon- floor, 2walls, 2 roof sections. It has no strength. Rafter ties make the roof a triangle, which is very strong. Given that its so small, you might be okay with collar ties half way up the rafters, but I'd do calcs to determine that. It would be easier and might look nicer. I still think you should take your design as built and get some professional advice with calculations based on the snow load in your area. The engineers that frequent this site have not commented on your design, they could help you iron out the specifics if willing. My off-the-cuff solution might be more than you need, or not enough, depending on snow load. Do you know what the design snow load is for your area? My cabin has a similar design but its twice the size, 14 x 24. I have no ceiling joists, but rather I'm using 5/8" steel rods as rafter ties every four feet. Even with a moderate snow load of 70 lbs per sf, actual roof snow load, I figure the tensile force on one of those rods is about 3000 lbs. The forces add up quickly with snow loads, even in small cabins. Of course that's worst case scenario but it only takes one heavy snow storm to ruin your whole day.

Don_P Member	# Posted: 1 Oct 2014 10:46pm Reply I haven't really followed along but was just catching up. I saw a couple of things I see pretty much the same but a little differently. A board is an inch, dimension lumber, or lumber, is 2-4" thick Heavy timber is 5x5 and larger These designations come from the grading folks, they correspond to grading rules and strength design values for each group. A beam could be any of them. A beam is a member that resists loads in bending, compared to say a column that resists loads in axial compression. Glulams are made with waterproof glues and can be made with treated lumber. There are glulam bridges. A rafter tie restrains the outward "toggling" force exerted by rafters. By code they need to be installed to every rafter pair in the lower third of roof height. A collar tie is a seperate member and is installed at least one every 4' in the upper third of roof height. It restrains the rafters in an uplift from high wind. These are two different members with different roles. The way to avoid an exposed collar tie is to run a metal strap over the ridge from rafter to rafter, this ties the roof planes together at the peak. A ridgebeam capable of supporting half the roof width removes the horizontal thrust at the rafter heels. There's not enough information, I'm not certain that the ridgeboard isn't capable of being a beam. If not with a little modification and a center tie it would probably be up to task. As devil's advocate, the plate logs themselves are probably capable of resisting the thrust for those spans if they are adequately tied to the gable logs. Instead of a ridgebeam resisting the roof load the top logs can act as beams to resist the rafters' thrust.

bldginsp Member	# Posted: 1 Oct 2014 10:51pm Reply Sometimes having an engineer around is a breath of fresh air.

JBruinsma Member	# Posted: 1 Oct 2014 10:52pm Reply County website says 50-60psf for my elevation I believe.

w8n4rut Member	# Posted: 2 Oct 2014 06:28am Reply Quoting: Don_P A ridgebeam capable of supporting half the roof width removes the horizontal thrust at the rafter heels. There's not enough information, I'm not certain that the ridgeboard isn't capable of being a beam. If not with a little modification and a center tie it would probably be up to task. As devil's advocate, the plate logs themselves are probably capable of resisting the thrust for those spans if they are adequately tied to the gable logs. Instead of a ridgebeam resisting the roof load the top logs can act as beams to resist the rafters' thrust. I agree with this statement. This is a 10'x12' building. If the ridge is supported vertically on the ends to bearing and the rafters are properly fastened to the walls and ridge you are more than adequate. I would hate to see you clutter up the inside with ceiling joists and collar ties if you didn't have to...

Don_P Member	# Posted: 2 Oct 2014 06:41am Reply Bldginsp, I'm a residential contractor, these aches and pains came the hard way

bldginsp Member	# Posted: 2 Oct 2014 08:00am - Edited by: bldginsp Reply Thanks Don for your input. So if relying on the eave walls to take the thrust, these walls should be strapped to the gable end walls. That will be difficult to do in an attractive manner, but Simpson makes some 'architectural' straps. And, the H clips holding the rafters to the top plate should be looked at, because if they are located to resist uplift they may not do anything for lateral thrust. The rafter-plate connection becomes key. A35 clips at rafter/plate may solve that. The ridge board will function as a beam in such a small building, but I see from one of the photos that the 'king post' for the ridge on one end of the building sits on a flat 2x4 header over a window, removing the value of the ridge board as a beam. The king post over the porch appears to sit on a beam/header stretching 10', can't tell what it is, should be more than 2x. These king post issues can be solved easily. Again I wouldn't be so nitpicky if it weren't for snow loads. If he's got a 60lb ground snow load, that translates into 70 lb roof snow load, with his eaves he's looking at roughly 170sf roof area in plan, which is almost 12,000 lbs total load for the whole roof, worst case scenario. I agree putting rafter tie/ceiling joists would look less than desireable, looks like a few fixes can avoid that. But I think leaving it as is would be risky, only because of snow. And, we haven't taken up the foundation issue, which is another ball of wax.

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