Building a Guest Room at the Cabin

   / Building a Guest Room at the Cabin #1  

GPintheMitten

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Flushing, Michigan
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My BIL and I are going to build a stand alone bedroom, guest "shed" at our family's cabin site next spring. We're making plans for a 12 x 16 one story room to be built on 4x6 treated runners a little ways away from the cabin.

The reason we are putting it on treated runners instead of a fixed foundation is that we don't need a building permit for structures that are movable below 200 sq ft. We probably won't ever move it, but just in case we must move it some day, we want to make sure we can move it without tearing it apart.

I've moved small out buildings before and I know they need to be reinforced for such. The largest one was 14x21 garage.

We have already removed a few trees and the stumps and leveled the ground. We are letting it sit over winter and will re-level as necessary in spring from any settling. The ground is very sandy with good natural drainage.

So here's my plan for the "foundation". It will consist of four 4x6 treated posts 16' long, spaced 4 feet on centers to make a 12' grid. Each 4x6 will be placed on solid concrete blocks 2"x8"x16" laid flat. We'll excavate about 6 inches under each place a block goes and put in gravel up to the normal soil level. The blocks will be placed 4' on centers for each runner and all made level.

Then the plan is to build a floor system using treated 12' 2x4's, 16" on centers for floor joists. The joists are only spanning 4'. Then glue and screw t&g 3/4 OSB . We'll probably build the floor in 2 sections and move them into place. The reason being, we want to be able to move the floor system before we place it on and fasten it to the 4x6 runners. We want to insulate the floor cavity and fasten hardware cloth on the underside to keep critters from making nests etc.

We will use a loader tractor to help with the heavy lifting. After fastening the osb to the 2x4's we will lift it or turn it over, insulate it, staple the hardware cloth, Then lift it again, turning it back over on top of the runners right side up. The we will fasten the floor system to the runners by drilling long screws through the floor through the 2x4's into the 4x6's.

I hope that is understandable. My concern is that if we later connect chains to the runners, that we can move it without it coming apart. I have thought about screwing 2x4 in the spaces between the runners at angles to brace them and make them more rigid.

So what do you think?
 
   / Building a Guest Room at the Cabin #2  
I question the use of screws. I don't think they will be strong enough for what you want to do - but I don't know for sure. Screws are designed to withstand pull out forces and not shear forces. I would think that using bolts would be better, but installing them would be a challenge with the way you plan to build. Ideally, you'd countersink the bottom of the skid for the head of the bolt and run it thru the skid, the floor, and the bottom plate of the wall.
 
   / Building a Guest Room at the Cabin #3  
Do I understand that the only thing between bare ground and the insulation will be hardware cloth. Seem like with fiberglass moisture would be a problem and foam I would be concerned about insects.

MarkV
 
   / Building a Guest Room at the Cabin #4  
Perhaps consider jacking it up and install concrete block piers under it to provide more clearance from the ground. It would still be a moveable building. I've moved a couple by jacking them up high enough to put a trailer underneath for the move which is easy on the building.
 
   / Building a Guest Room at the Cabin #5  
Have you thought about buying a couple of cheap surplus mobile home axles and tires and mount the axles only, retaining the tires for later - the axles will just stay under your sill plate and if you never move it..no harm done..but if you decide to move it..you just dig out a little under the end of each Axel and mount the wheels and pull it where you want it...Just a thought.
 
   / Building a Guest Room at the Cabin #6  
Your proposal sounds like it will work fine. I would only make a few suggestions.

I would recommend that you use only two runners under the floor, this would make it a whole lot easier to move if needed and you might consider using a 6 X 6 instead of the 4 X 6. You would place these in about 2' from the side which would reduce your span to about 8'. I would up size the joists to a 2 X 6 for the longer span and you can increase the insulation thickness,you really don't need PT for these.

I would also suggest that you use plywood instead of the hardware cloth (1/2" CDX would work). You would treat the underside of the building the same as you would the walls use a vapor barrier on both sides of the joists.

If you use plywood on the underside of the floor joists you could frame the floor first, then put on your vapor barrier and the plywood on the underside while it is turned upside down then turn it right side up and fasten it to the runners. You could use screws in a "toenail" fashion for this part. You also should use a row of blocks between the joists for more strength if you used two rows positioned over the runners you would have more points for fastening to the runners.
Next you would insulate and then put on you 3/4" OSB. The floor is then ready for walls. You would put a vapor barrier on top of the OSB under your sub floor.
I worked for a company years ago that built there own job shacks with this same design and we moved them about once a year from job to job without any problems. We would load them onto a flatbed dump truck by lifting the end of the shack and raising the truck bed and then backing under the shack. To unload just raise the bed, dump and let it slide off. The shacks were 8' X 16'.
 
   / Building a Guest Room at the Cabin
  • Thread Starter
#7  
Thanks for all the suggestions. I'm confident in the design and construction of the basic building but not in the foundation plan. So I appreciate all the helpful ideas.

TRR - Good point about the screws.

MarkV - Yah, the hardware cloth would rest on the top of the 4x6's so it would only be 5 1/2" above the grade. We were going to put down plastic sheets on the ground before we lay down the 4x6's but I agree, we are susceptible to moisture and bugs.

The hardware cloth was my bil's idea. I wanted a layer of plywood like billybobjimmyjoejack suggested. My bil was concerned about moisture condensation.

Opti-Mist - I think you're right, the building needs to be off the ground more. I think we were trying too hard to keep the building low so there would be only a short step up into it. But I think it would be worth another step or two to get more air space under it to keep moisture problems down and to be able to ready it to move if we ever had to.

brin - good idea about axles. I'll keep that in mind.

billybobjimmyjoejack - You need a couple more first names :laughing:

You suggestions are more in line with my original plan ... to sandwich the joists between 2 layers of ply... and build it upside down first to etc. My bil suggested the hardware cloth because he was concerned about condensation. But maybe wrapping it with moisture barriers on both sides will take care of that.

Hmm, 2 runners instead of 4, that just might be the way to go. I was trying to figure out how I would keep all 4 runners square if I had to move the building but I think we would get pretty good connection to the 2 runners with your suggestion and by using 2x6's we surely can space 8 feet and have 2' overhang.

Here again, it would add some height in stepping up, but that is probably worth it.

Billybob... etc. - I'm not sure I understand this part:

You also should use a row of blocks between the joists for more strength if you used two rows positioned over the runners you would have more points for fastening to the runners.

At first I thought you were talking about concrete blocks. Are you talking about 2x6 blocks nailed between the joists? Oh,,,, wait a minute, that must be it. OK, I think I get it.


All - thanks much for your responses. It will certainly make our project work better in the end. I'll have to talk to my bil and see if he agrees. But I think you guys put me on the right track.

Thanks!:)
 
   / Building a Guest Room at the Cabin #8  
You got it. You're welcome.
 
   / Building a Guest Room at the Cabin
  • Thread Starter
#9  
It's almost spring and we are making our final plans for the construction of the Guest Room.

I have some questions. We will build rafters in place, rather than use trusses. The guest room will be 16x12 and then 4 foot covered porch. So the entire roof will be covering 12 x 20. Does the ridge board have to be one piece or can it be 2 pieces butted together?

Also, if we have a 1 foot overhang on all 4 sides, the ridge board still ends at the building envelope rather than including the 1 foot overhang on each gable end, right?

For the foundation, we are looking to go with 3 runners, 6x6 treated, 20 feet long. With one under each side wall (no overhang) and one in the middle. We'll use 2x6 joists 16" o.c. with the blocks between the joists along the middle runner to give us more attachment of the building to the runners.
I plan on gluing the floor joists to the runners and lots of stainless or other type of nails suitable for treated boards using a framing nail gun.

Then I'll glue and nail the 3/4 osb to the floor joists and in turn glue and nail the bottom plate to the subfloor. I think that will get me good connection to the runners in case I need to ever move the building.

My bil still wants to go with hardware cloth on the bottom of the floor joists to keep out critters, and avoid moisture build up. We will put down a layer of visquine on the ground. We'll probably insulated with pink styrofoam cut and stacked in the joist bays.

I'm also thinking that if the time ever came to move the building, I could reinforce the runners rigidity with some steel cross pieces.

Btw, we will build the floor joists system upside down with the hardware cloth on top and some temporary diagonal bracing. Then flip the grid over and place it and connect it to the runners before insulating and putting down the 3/4 osb subfloor.

How does this modified plan sound?
 
   / Building a Guest Room at the Cabin #10  
GPintheMitten said:
It's almost spring and we are making our final plans for the construction of the Guest Room.

I have some questions. We will build rafters in place, rather than use trusses. The guest room will be 16x12 and then 4 foot covered porch. So the entire roof will be covering 12 x 20. Does the ridge board have to be one piece or can it be 2 pieces butted together?

Also, if we have a 1 foot overhang on all 4 sides, the ridge board still ends at the building envelope rather than including the 1 foot overhang on each gable end, right?

For the foundation, we are looking to go with 3 runners, 6x6 treated, 20 feet long. With one under each side wall (no overhang) and one in the middle. We'll use 2x6 joists 16" o.c. with the blocks between the joists along the middle runner to give us more attachment of the building to the runners.
I plan on gluing the floor joists to the runners and lots of stainless or other type of nails suitable for treated boards using a framing nail gun.

Then I'll glue and nail the 3/4 osb to the floor joists and in turn glue and nail the bottom plate to the subfloor. I think that will get me good connection to the runners in case I need to ever move the building.

My bil still wants to go with hardware cloth on the bottom of the floor joists to keep out critters, and avoid moisture build up. We will put down a layer of visquine on the ground. We'll probably insulated with pink styrofoam cut and stacked in the joist bays.

I'm also thinking that if the time ever came to move the building, I could reinforce the runners rigidity with some steel cross pieces.

Btw, we will build the floor joists system upside down with the hardware cloth on top and some temporary diagonal bracing. Then flip the grid over and place it and connect it to the runners before insulating and putting down the 3/4 osb subfloor.

How does this modified plan sound?

Of course the ridge board can be spliced. Splice between rafters, and add cleat boards on both sides of splice nailed to ridge and end nailed to both rafters.

As far as the overhang...we used to frame everything back tied into the second truss/rafter by cutting notch pockets and installing lookouts. Nowadays, the overhangs are built on the wall section flat on the deck. Only tied into the roof when the roof is sheeted. IMHO, the old way was better, the new way is faster/cheaper/easier.

As far as your skids are concerned, I would cut a 22 degree bevel mimicking a boat front. Spacing is fine. If you ever need to move it, I would take a 12' 6x6 or piece of steel and run a chain to each skid, then hook two chains back to your tractor. I think this way you will keep the torque even on the skids.

One added measure, I would add some hurricane ties to bond the skids to the joists. They make dozens of configurations, but something along the lines of the attached picture.

image-3320328278.png
 
 
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