have question about timber frame floor system

[platinumphoenix]

This is my first posting. Hopefully all goes well. If I'm posting in the wrong place let me know. Etc...

I'll keep this summerized because I don't know what info is needed to answer these questions. I'll write a novelette if you let me.

In a nutshell. I bought a plan from timberframehq.com. I realized the frame had no floor so I retrieved a floor blueprint from timberframehq.com
Here are questions
- I feel the floor plan is to small to carry the load of the frame and the walls roof and contents. I tried using the calculators but I don't know the weight of the wattle and daub. How do I go about fixing this?
-Can scarf joints on the sill be below posts? Or do they have to be between posts?
-is it ok to put my timberframe cabin on a pier foundation or a  concrete footing foundation? I'm trying to avoid slab because the location is just on a hills edge. Three foot drop in elevation at 20 foot length.

Thank you for reading.

[Don P]

Welcome to the forum.
For question 1, wattle and daub is going to be lighter than brick, I'd use masonry weight.
#2 I'm not particular where or if you use a scarf in a sill because
#3 build on a continuous perimeter foundation, piers require engineering and generally by the time that is done correctly, the full perimeter would have been cheaper and stronger.

[firefighter ontheside]

Is there no plan review by the local county or city where you will build.  Of course my county has that, but they had little experience with log homes.  There only contribution was that I needed a 24" footing and 10" pour instead of the normal 18" footing and 8" pour.  My log home builder suggested that my 2x10 floor joists be perpendicular to the foundation on all 4 sides to help support the weight of my logs that average about 15" diameter.  After 22 years it is doing just fine.

[Don P]

You're lighter than a conventional brick house. Nothing wrong with what they had you do FFOTS, but nothing right about the logic. They looked at "big" logs and didn't think that they actually weigh less per square foot of wall than brick does. 

Quantify the loads
Quantify or make prescriptive assumptions about soil bearing capacity
Put a big enough footing down below frost depth to resist the load without sinking.

[platinumphoenix]

Welcome to the forum.
For question 1, wattle and daub is going to be lighter than brick, I'd use masonry weight.
#2 I'm not particular where or if you use a scarf in a sill because
#3 build on a continuous perimeter foundation, piers require engineering and generally by the time that is done correctly, the full perimeter would have been cheaper and stronger.

Thanks. I will choose a continuous perimeter foundation then. I have to do some research to make sure it's properly done.
I'll use masonry weight. I can find the weight for cinder blocks. It seems to me that it would work unless you advise against it.

[platinumphoenix]

Is there no plan review by the local county or city where you will build.  Of course my county has that, but they had little experience with log homes.  There only contribution was that I needed a 24" footing and 10" pour instead of the normal 18" footing and 8" pour.  My log home builder suggested that my 2x10 floor joists be perpendicular to the foundation on all 4 sides to help support the weight of my logs that average about 15" diameter.  After 22 years it is doing just fine.

Yes I live in the deep woods of South East Missouri. So the laws are minimal. The basic law is, as long as what I do doesn't hurt the woods and wildlife, they don't care. I have never heard of an inspector or anything. And I own my property outright. So unless someone call police I'm not likely to have the government around. My main concern is building the cabin so that it is safe to live in for me.

[platinumphoenix]

I needed a 24" footing and 10" pour.

After 22 years it is doing just fine.

Bravo on building a sturdy home. I admit I'm nervous since this is my first large structure. And my experience has been in finishing traditional stick build housing and exterior masonry. But I know my limits. So as long as I measure twice and cut once. I'm sure it will come out ok.
Does 24" footing and 10" pour refer to 24"x24" footing with a 10" slab?

[firefighter ontheside]

I'm not that far from you.  I'm about 30 miles south of Stl.  The county just to the south of me has not building code.  All they have to do there is get an electrical inspection.  The footing is 24" wide but I believe only 10" deep.  They just wanted to it to have a wider foot to distribute the weight.  The foundation walls are 10" thick where standard for framed house is 8".

[platinumphoenix]

I can manage that sort of foundation. Thank you. It's good to know I have a friendly neighbor. ;D

[Don P]

Foundation wall thickness and reinforcement is more about resisting lateral pressure from the soil.

We have designed for 7' of unbalanced fill on the current job, a completely submerged basement. The dirt is 7' higher outside than inside. This requires 12" block with 5/8 rebar in poured cells every 4' along the wall.

Chapter 4 here is your friend;
Digital Codes (iccsafe.org)

I would keep digging for a weight of wattle and daub, you are not the first. Somewhere on a green building forum...

If you do use concrete block remember timberframe collects load to discrete points very often, pour those cells solid under point loads.

Edit;
Well, looks like there is a new chapter in the back of the codebook, cob, I'm just cracking into it, might be helpful;
APPENDIX AR LIGHT STRAW-CLAY CONSTRUCTION, 2021 International Residential Code (IRC) | ICC Digital Codes (iccsafe.org)

It looks like 30lbs/cu ft is not out of line... then how thick is it, check the thermal info in there for more.

[platinumphoenix]

Foundation wall thickness and reinforcement is more about resisting lateral pressure from the soil.

We have designed for 7' of unbalanced fill on the current job, a completely submerged basement. The dirt is 7' higher outside than inside. This requires 12" block with 5/8 rebar in poured cells every 4' along the wall.

Chapter 4 here is your friend;
Digital Codes (iccsafe.org)

I would keep digging for a weight of wattle and daub, you are not the first. Somewhere on a green building forum...

If you do use concrete block remember timberframe collects load to discrete points very often, pour those cells solid under point loads.

Edit;
Well, looks like there is a new chapter in the back of the codebook, cob, I'm just cracking into it, might be helpful;
APPENDIX AR LIGHT STRAW-CLAY CONSTRUCTION, 2021 International Residential Code (IRC) | ICC Digital Codes (iccsafe.org)

It looks like 30lbs/cu ft is not out of line... then how thick is it, check the thermal info in there for more.

That all looked like the answers I was looking for. Thank you. If anyone else has anything else to add feel free. Once I update my plan I'd like to have a friend check it lightly for glaring errors. Is there a specific place for that here on the forum?

[Ljohnsaw]

Another option on a foundation.  I used a product called FasWall.  There are a few different manufactures of similar products.  They are blocks made from 85% recycled pallets and 15% Portland cement.  Technically they are considered ICFs.  Mine were 24" long, 8" high and 12" wide.  They come either hollow or ~half filled with rock wool or polyiso.  In my case, every cell (12") vertically a #5 rebar and every other row (16") a #4 stick.  They are mortared to the footing and dry stacked the rest of the way up.  So it goes up pretty fast.  Then you pump in concrete.  Where ever there will be a timber post, you remove the insulation so the entire column is filled with concrete and a special Simpson bracket is embedded in the concrete to anchor the post.

The start

Midway

Details of the blocks and rebar

[Prizl tha Chizl]

Well, looks like there is a new chapter in the back of the codebook, cob, I'm just cracking into it, might be helpful;
APPENDIX AR LIGHT STRAW-CLAY CONSTRUCTION, 2021 International Residential Code (IRC) | ICC Digital Codes (iccsafe.org)

It looks like 30lbs/cu ft is not out of line... then how thick is it, check the thermal info in there for more.

Just to clarify, wattle and daub, (woven sticks or lath covered in a mixture of mud, clay, sand, dung, etc.) is not light straw clay, (straw coated with a thin clay slip, packed intro a wall cavity or movable form as insulation and infill.) Light straw clay is a modern wall infill system based on traditional timber infill in France and Germany, and could be used to insulate a wattle and daub wall, however wattle and daub could stand alone with no insulation or be insulated some other way. 
I'd assume wattle and daub to weigh similar to wood lath and plaster, which the Internet is telling me is 10#/sf.
The actual weight of LSC systems varies widely depending on the clay content of your specific mix, and 30#/cf seems heavy to me for a mix that is going to have good r value, but code had to assign something, so probably a safe number to design with.
Never done wattle and daub, but it always looked like fun to me. I've worked on a number of LSC projects and happily reside in one of them- warm in winter and cool in summer, quiet to boot. More info here http://www.lightstrawclay.org/

[platinumphoenix]

I have the plan finished. I'm looking to post it. I'm not sure where to post it yet, I'll figure it out. I'm going to see if anyone find any major scary flaws in the plan. And I'll keep researching in case there is something in need to factor in I forgot about. The basic set up will be a wrap around footing, no slab, brace and tenon frame, wattle and daub, with an insulated tin roof. All of it ready to be altered if necessary.
The biggest problem I had is figuring out the weight load the concrete can handle. But based on all the components I do know about, I don't see any reason there would be a overload.  Is overload the right word? 🤔🤷

[Don P]

Post the sketches here, if you would like more eyes. To be honest I'm not sure if I've ever put a plan in the repository  :D.
Concrete is typically good for 3,000-10,000 pounds per square INCH in compressive strength. That is rarely the issue as the soil under it is capable of those loads per square FOOT.

[platinumphoenix]

Well ok. Here it goes.

Part of the plan is hand drawn. Part of it is purchased. I have no interest is selling or advertising. I'm not posting the full purchased plan, only three pictures of a ~30 page plan. I believe that's allowed with fair use. If not, please forgive. So if the plan looks incomplete in the future it may have been partly taken down. Please DM me.

The plan is also assumed to be incomplete. So if you want to use it double check EVERYTHING. Assume there are mistakes.

Personally I'd be willing to start building. But I'm not an expert so my opinion (humbly) means nothing.

 

 

 

 

 

 

 

[Don P]

If this is a foundation and floor question, just a general perspective from the purchased plan is probably a better swap out for those last pics.

On to the foundation and floor.  I could not read the notes on the footing detail?
If this is 10'x20' I'm not following the need for a center girder in the floor?
On the 2nd pic from the top it mentions joists bearing on 2" of concrete. Minimum bearing of treated or naturally decay resistant wood on concrete is 3"... 1-1/2" on wood. But, this floor and foundation is using a good bit more material than necessary, is stick framing the floor an option?
The floor plank detail soared right over me?

[platinumphoenix]

If this is a foundation and floor question, just a general perspective from the purchased plan is probably a better swap out for those last pics.

On to the foundation and floor.  I could not read the notes on the footing detail?
If this is 10'x20' I'm not following the need for a center girder in the floor?
On the 2nd pic from the top it mentions joists bearing on 2" of concrete. Minimum bearing of treated or naturally decay resistant wood on concrete is 3"... 1-1/2" on wood. But, this floor and foundation is using a good bit more material than necessary, is stick framing the floor an option?
The floor plank detail soared right over me?

All fair points. I'll look into changing the picture quality. It looked clear on my phone. Guess I lost quality in the upload somehow.
- sorry I'm not understanding the first comment I think. The building frame plan I purchased does not include a floor plan. I had to ask for a floor plan from them. They gave it for free. But I had to resketch it anyway since it wasn't the right dimensions.  I suppose stick built floor is possible. I like to avoid it if I can. I have reasons for not liking stick built, could name a dozen, instantly, if you woke me from a nap. But that's a story for later.
It's a single room 16'x20' cabin. The reason for the center sill and foundation is because (...I live in an extremely tight spot waaaaaaaayy out in the woods. 22 miles of graded road. The last 2 miles is almost a foot path that won't fit a large vehicle without scratches. 45-50min from home to town. If I speed up a bit.
So...) any cut lumber longer then 10' is going to be a bitch to get back. So having the floor in 12-15 pieces  scarf jointed together is about as good as it gets. And I'm not 100% that will work. One thing at time.

The concrete footing is supposed to insure the sill is strong. The joist will be fitted into the sill rather then nailed or set directly to foundation. So the extra concrete lip is just an added security I notice I could get if I adjusted the dimensions.  

I'm not sure how to reduce material any further. Perhaps the foundation. I copied it from firefighter ontheside's description earlier in this post. I figured a timber frame probably won't be near as heavy as a log cabin.

The floor joists will double as the groove portion for slat/groove flooring. Did I explain it well?

I'm only explaining my thought process on these matters. I'm not arguing. If any of these ideas I concluded are still bovine excrement let me know.

[Don P]

Nope, we're good, I'm a fan of plain speaking. 16' is getting into needing a mid girder I thought I was seeing 10' and was scratching my head. That is only supporting a floor load and the lateral bracing for the building is supplied by the perimeter foundation walls. All that to say a mid girder is typically supported by piers and posts.  I would drop the center girder under the joists in that event. Although the center foundation wall you have drawn is certainly stronger. Make sure you can access and ventilate all of it though. 

8" thick foundation walls is plenty if your joists are bearing on/ in the sills. Trying to pick up 2 bearings on different materials... well, pick one, you won't end up bearing on both. If the heavy timber sill is not treated, I put a treated 2x on the concrete foundation then the untreated 8x8 sill on top of that. 

[Ljohnsaw]

I figured a timber frame probably won't be near as heavy as a log cabin.

Yes, a log built cabin will be heavier than timber frame but what is your snow load?  That will probably preclude the weight of the logs/timbers.  Also, the timer frame will be more point loads on your foundation and footings.  Your 10" thick x 24" wide footings should be sufficient.  I did 12x24 for my timber frame with 340+ pounds/sq-ft snow loads.

[platinumphoenix]

Nope, we're good, I'm a fan of plain speaking. 16' is getting into needing a mid girder I thought I was seeing 10' and was scratching my head. That is only supporting a floor load and the lateral bracing for the building is supplied by the perimeter foundation walls. All that to say a mid girder is typically supported by piers and posts.  I would drop the center girder under the joists in that event. Although the center foundation wall you have drawn is certainly stronger. Make sure you can access and ventilate all of it though.

8" thick foundation walls is plenty if your joists are bearing on/ in the sills. Trying to pick up 2 bearings on different materials... well, pick one, you won't end up bearing on both. If the heavy timber sill is not treated, I put a treated 2x on the concrete foundation then the untreated 8x8 sill on top of that.

Thanks you. I think two pier posts should support the mid girder just fine. I'll make the post 8x8 similar to the floor frame. A simple grate vent for ventilation. I'm not sure why I should access the crawl space since there won't be any pipes or wire down there. I could keep a two foot crawl space opening at the lowest part of the tallest footing wall. I don't think that would compromise the strength of structure.
I can put a 2x8 between the foundation and sill. Sounds good to me.
"Trying to pick up 2 bearings on different materials... well, pick one, you won't end up bearing on both." - I'm not sure what you mean here. Are you referring to the 2inch concrete lip I had planned into the foundation? If so, then this makes sense. But I take your advice and go to pier anyway.

Correction. At least one grate vent for each wall. So, 4.

[platinumphoenix]

I estimated snow load at 30lb. I'm getting the feeling that number is seriously flawed. But I also got the feeling snow load won't be an issue.

[Don P]

It sounds like the clear span of the center girder between piers is ~6' x half the building width, 8'=48 square feet of floor load on the sections of midpan girder between piers. Figure 50 lbs per square foot x 48 sf= 2400 lbs uniformly distributed load. You can check your beam against that load. The perimeter sills are fully supported so no beam check needed there. Yes those are carrying the snow load so probably not a concern unless you are in a high snow load area. This should take you to current data for your location;
ASCE 7 Hazard Tool

Crawlspaces need to be either completely sealed and mechanically conditioned or built dry and well ventilated. Cool and dank is rot. From the stepping drainage around the footing in washed rock, parge and tar the foundation below grade and take the drains out to daylight downhill. Inside the crawlspace remove anything organic, bugs smell from decay. Make access to everywhere for inspection later. Grade the soil to drain with no pooling spots. Cover that with at least 6 mil plastic to keep soil moisture out of the air under there. Under this house I poured a thin ~2-3" thick slab over gravel and plastic with a drain out. There is no floor load to speak of the slab has me on my knees for load but it is a dry sealed floor. Your 2x2 access is minimal, the 8x sill can easily span that. Our water heater lives under there. And they got bigger by the thickness of more insulation, I barely got it in through my access door that was large enough for the original. The main goal is make it accessible everywhere under there and keep it dry.

[platinumphoenix]

It sounds like the clear span of the center girder between piers is ~6' x half the building width, 8'=48 square feet of floor load on the sections of midpan girder between piers. Figure 50 lbs per square foot x 48 sf= 2400 lbs uniformly distributed load. You can check your beam against that load. The perimeter sills are fully supported so no beam check needed there. Yes those are carrying the snow load so probably not a concern unless you are in a high snow load area. This should take you to current data for your location;
ASCE 7 Hazard Tool

Crawlspaces need to be either completely sealed and mechanically conditioned or built dry and well ventilated. Cool and dank is rot. From the stepping drainage around the footing in washed rock, parge and tar the foundation below grade and take the drains out to daylight downhill. Inside the crawlspace remove anything organic, bugs smell from decay. Make access to everywhere for inspection later. Grade the soil to drain with no pooling spots. Cover that with at least 6 mil plastic to keep soil moisture out of the air under there. Under this house I poured a thin ~2-3" thick slab over gravel and plastic with a drain out. There is no floor load to speak of the slab has me on my knees for load but it is a dry sealed floor. Your 2x2 access is minimal, the 8x sill can easily span that. Our water heater lives under there. And they got bigger by the thickness of more insulation, I barely got it in through my access door that was large enough for the original. The main goal is make it accessible everywhere under there and keep it dry.

I heard all that. I'm off to the drawing board to build a better foundation. I'll be back soon.
In the mean time. Cats rule! Dogs drool!
Meet my sweetheart kitten Tea-Lilly. Born July 23rd.


 

 

 

[Don P]

I'm sitting here with an old pup that wanted to get up at 3 am, for whatever reason. He's back out, I'm up. Critters rule the roost :D.
One thing I forgot the other day, look beneath the center post in your previous sketch, it is over a step in the footing. not a big deal but if the post can be over a level section  it would be better to be away from a stress concentration.