Hi all,
New guy here, name is Jon, been a subscriber to FHB for about four years, I usually post questions to Usenet, but the stuff I need answers to is way beyond the level of knowledge available there.
Anyway, I’m a civil engineer, who has some architectural experience, I am trying to develop a complete set of plans for a new timber frame home for myself and my family. I’ve nailed down a lot of the materials and details, but there’s a few things that I can’t get any good information on, and I thought maybe I would turn to this forum. FWIW, I have asked several different architects in my area, who I work with regularly, if they had any experience with timber framing. Only one did, and he has no parctical construction experience, only conceptual design.
Here’s the questions:
1. I am going to use ICF’s for the basement, it will be a walk-out basement with a stone veneer on the exposed parts. On top of the ICF wall, I’d like to place a plate and use open-web floor trusses for the first floor. How do I support the timber frame? Do the ends of the frame columns have to sit directly on the ICF wall, or do I transfer the load with some sort of bearing plate? The framer I’m using hasn’t worked with ICF walls before, only plain concrete, so he doesn’t know what the overlap needs to be, if any. Let’s just say we’re both confused.
2. The house will have a full basement below the floor trusses, so no problems running wiring or plumbing. Between the main floor and the second floor, though, will just be exposed floor joists and tongue-and-groove planking. The second floor will have two bathrooms. How the heck do I run waste piping for this? Do I need to install plumbing and wiring chases?
3. Having trouble figuring out how to deal with air exchange and cooling. The floors will have radiant heat (I am going to use Warmboard unless someone can convince me otherwise), but that doesn’t solve the air exchange requirement for a very tight house, or the desire for use to have air conditioning of some sort. I hate forced-air ductwork, so I was thinking of a mini-split or a through-wall unit (or maybe a Space-Pak type unit) to cool the house. I need to be talking to a good HVAC contractor, but it seems all the guys in my area are old-school, can’t deal with new tech and new methods.
Hey, sorry about the long first post, but I’m trying to save every dime I can by making this house a DIY special. Not sparing a cent when it comes to materials and workmanship, but most of it I am going to be doing myself (basement, siding, interior finishes, all cabinetry, painting, etc. Even installing my own septic system.)
Jon E
Replies
Try contacting the Timber Framers Guild. They have a website you can do a search to find it. Try asking them. They're terribly experienced at that stuff, great bunch of people too.
Jon
The man here you need to talk to is frenchy. He's building a timber frame house, and has several books on the subject. He can guide you to the ones that are worthwhile.
He may also warn you that this is an incredibly labor intensive way to build a house. Of course, if you like to do this sort of thing and have either the time to do it, or the money to pay for it, then build it the way you want it.
P.S. I need to email him on something else, I'll mention this discussion to him.
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I would place a timber for a sill on the ICF wall and hang the webjoists from it and notch the upright timbers for the main level into it. i suppose that you could anchor timbers on a plate and then hang a ledger for the joists to mount onto
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You said no p[roblem with plumbing and wiring and then elaborated on the first of many problems you will find with it. Yes, you need a chase or to develope a sense of humour when the appraissor askes about the pipes he sees.
Good design layout avoids that problem as much as possible. for instance, my upper bath drops into the laundry room so the pipes can be hidden in a cabinet or a soffit. Sometimes a strategic closet placement helps.
Excellence is its own reward!
Is there any reason I shouldn't be putting a PT plate down on the sill first, and then putting a timber down on that? This part of the process, the frame-to-foundation connection, is the only thing right now that's stumping the hell out of me. If I'm going to have 8" of concrete sandwiched between 2 layers of 2" foam, then does the plate need to be 8" wide or 12" wide? And then, how do you deal with the exposed foam? And if I put a 12" wide plate and an 8x8 sill beam, what do I hang the trusses on? The plate or the beam?
I'll tell you what, being a civil engineer, this is something that frustrates me to no end, when I can't visualize something. All I need is a picture..... :)
Jon
picture with potential.
Excellence is its own reward!
OK, that looks fine, about what I thought, but two questions:
1. Is there enough bearing area on what's left of the sill plate to put the ends of the trusses? It looks like I'll only have about 3", maybe 3-1/2 at best.
2. What do you do about the *space* between the ends of the joists and the inside face of the stress-skin panel? Does that get filled with some kind of blocking?
I think if I installed some kind of ledger board or truss pockets at a point below the top of the wall, such that the top of the truss would be even with the top of the sill beam, I'd be OK. Just need to figure out how to do that with an ICF form.
3" should be plenty of bearing surface for your joists. The technician who sells you your joists will be able to confirm this.
The people who sell you your joists will want you to buy panel blocking to put in between the joists where they bear on the plate. That is short lengths of joist material. It gives the lumber yards an opportunity to unload their off-cuts at a 0% discount. What I have talked the engineers into letting me do in the past is simply to fasten 2x4 blocking to the SIP between the tops of the joists. The rationale for the panel blocking is to prevent the joists from rotating under live loads. Nailing the bottom flange to the sill and blocking between the top flanges does the same thing and it's waaaay cheaper.
Hi Jon,
I'm frenchy, i've already solved many of the problems you are working on so maybe i can give you a hand.. don't be afraid to e-mail me any questions direct click on my name and you'll get my e-mail address..
to answer your questions ..
I used ICF's too so I should have your answers..
You need to carry the load path down to the concrete.. There are two basic ways to do that (and a hundred variations) while you can run the timbers downt to the concrete (make certain that you use a vapor barrier of some kind if you do. copper flashing is what I used, but aluminum will work as will poly.. just don't expect the same life out of them as copper) you can also set the timbers on the floor if the load path is strong enough to carry the load..
one technique that is often used is to use a carry beam and set the timbers on that. you of course could set it on a bottom plate and then use the bottom plate as the base for your floor joists too.. that will allow you to kill two birds with one stone.. assuming the footings are wide enough, you can use the bottom plate and to carry the timber on one half and use the other half to carry the Sips.. that way you will not have the cold floor problem that occurs when the bottom sill is uninsulated..
If you are wondering how much you can cantaliver a beam the usual rule is 2/3 load bearing can support 1/3 cantalievered. thus a 8x8 inch beam should have about 5 3/4 inch on the concrete and you'll net out almost the same as if it where loaded fully on the foundation.. wood type enters here..
as for Water, drainage, plus electrical.. run it up the back side of closets.. and when finished put a false panel in the back of the closet.
Air conditioning.. is a real issue that has many solutions yet none of them are great.. what I finally decided on was to go with window units.. I live in Minnesota and the number of days that require A/C to live is less than 30 a year.. espcially since the house is so well insulated with the use of SIP's. You mentioned one solution the other is to run mini vents up the same back of closets that everything else is running at. The placement of bathrooms gets very critical with a timber frame.. venting them is a critical issue and will force some compromises that you might not otherwise select..
as for your air to air exchange unit. you could do what I plan on doing. Put it in your attic.. that way a simple ceiling vent will provide the air intake and then you duct the returned air into the basement thru the walls of that same closet. assuming that you use sheetrock on both sides of it that is rated for fire resistance (type X) and cut holes in the top and bottom plates you shouldn't need to do any sheet metal ducting..
Careful Frenchy.
The 2/3 - 1/3 rule is for cantileevering but you described an offset beam. Totally different situation, depending on what loads above it and how. There are plenty of circmstances where following that advice will roll that timber right off the foundation..
Excellence is its own reward!
Piffin.
One of the wonderful things about timber frames is how easy it is to follow the load path.. If the load path is directly down, there is no reason to worry about a timber rolling of it's foundation.. the only weakness in this situation would be shear resistance, another words would the timber shear vertically.
If you check the capacity of the timbers used in timberframing. a typical 8x8 timber (which is the smallest fire rated size) can carry well over 15 tons.. if only 2/3rds of that load is on the foundation The load capacity of a single timber will probably exceed the total load by a massive factor..
However you are correct.. I can envision a couple of odd situations where with acesemtrical loading and an undersized beam where you might get into trouble.. assuming you either don't anchor the timber in place or have an unstable foundation prone to shifting..
Here's one I see often;
The sill beam is an 8x8 or even up to 12x12, but the posts seating to it are 6x6.
I remember replacing one sill that was 10x12 with 6x6 posts. The sill offset the foundation granite by 3-1/2" so most of the post loading was overboard. The sill was squashing and rolling. I jacked the house up, replaced the sill and built a new foundation complete with drainage system. Should be good for another hundred years..
Excellence is its own reward!
the rot was caused not by the offset loading but by the moisture absorbed thru the masonry that the frame sat on..
If an effective vapor barrier had been used the house wouldn't have needed the repair..
Actaually, thre rot was caused by roof runoff splashing onto plantings near the base and keeping the wal and timber wet. They didn't have or use PY back a hundred years ago. They went with white oak, heart pine, or Hackmatak.
Excellence is its own reward!
We work with a timber framer on some projects. He cuts and raises the frame and is also responsible for the panellers. We GC everything else including providing a conventionally framed deck to his specs. He notches his columns for the floor framing and runs them through a hole in the floor to the sill. I am sure the same could be done with floor trusses. We use conventional framing for the second floor bathrooms and run the pipes up a 2x6 interior wall. It requires a little more planning than a conventional building but is simple if you are a little flexible. It is good to talk to all the subs before you finalize your plans. Especially the electrician.
Jon,
We too are a timber frame owner / builder having just moved in about a month ago. We did not use ICF for the basement but rather conventional formwork. We have a walk out basement and the "4th" wall is framed 2x6 on 16-inch centers. We used full span truss for the 1st floor support. They are drop in truss where they rest on the foundation but the bottom of the truss sits on the top plate of the 2x6 wall on the walk out side. We used 24-inch deep truss on 19.2 centers and they worked very well. Made the foundation 10' 6" so we have 8' 6" clear below the truss. Foundation wall is 10 thick except where posts from the timber frame rest and here we made it 12 inch thick for a distance of 18 inches. On the concrete foundation we have a 2x10 treated mudsill and then 2 high 2x4 laid flat followed by the sub floor. (Same thickness as the tails of the drop in truss.) The SIPs then rest on the sub floor. Where the posts fall on the foundation we used full blocking to carry the post load down to the 2x10 mudsill with an addition on the inside to bring the full width of the 8x8 posts on to the foundation. On the framed (2x6) wall the SIPs rest on the top of the sub floor that is install on the truss but the posts loads on this wall are carried to the footer by means of a 3 1/2 inch schedule 40 pipe column that sits just inside the 2x6 framing. Truss layout was very carefully done so that none of the posts fall on the trusses. My truss span is 28 feet. We also have a line of center posts in this house – in fact two lines that are 5 feet apart. The loads form these posts are carried to large center footers again by the specially fabricated 3 1/2 inch steel columns. (each column carries a load of about 10,000 pounds.) These columns again "miss" the trusses and support the post directly. There is about 4 inch of blocking on top of the pipe columns between the posts and the base of the 8x8 posts. Each pipe column has a 6 x 8 inch piece of 6-inch channel welded at the top and bottom to transfer load. I have called these 3 1/2 inch steel columns – they are 3-inch schedule 40 steel pipe. Since I was set up to do steel fabrication, these were easy for me to do.
I really like the truss to work with and the 19.2 centers worked well. 1st floor is very stiff, we have 3/4 sub floor followed by 1/2 plywood underlay and then 3/4 oak strip floor. (Tile in kitchen and bath).
Plan on doing a lot of work in these truss especially for the electrical – the nature of a timber frame means that you will have lots of junction boxes for the wiring in these trusses in the basement. We also ran our HVAC, forced air in these trusses. We located the furnace unit in its own unheated room and it is vented to the outside for combustion air. (One high vent and one low vent) I also have the furnace / AC set up so that I can bring in a limited about of make up air from the separate "furnace room". This in effect is outside air. We are in western NC and our winters are not too cold so I have not worried very much about having this "cold room" in the basement. It is insulated from the rest of the basement. None of this will work for you since you are not planning to use force air. I do think that air exchange units to bring in make up air are made and I think with the very tight construction of SIPs you will need something.
As to second floor bathrooms – we stacked ours about the first floor baths and laundry room and used a false (drop ceiling) in these. Our first floor is 10 foot ceiling so we and lots of room (2 feet) to work with. I would try for at least 9 foot ceiling on the first floor so you have room to work. Remember not only do you have waste piping to deal with but also it has to run below those 6x8 floor joist beams. Make sure you plan all of this very well ahead of time – with layouts for the tub, shower, and WC. Again, you can't cut one of those 6x8 beams for the toilet flange. Also, make sure you plan where you are going to run waste stack vent (or vents) through the 1st and 2nd floor areas. We were able to use just on main stack and hide it at the back of the laundry room and basement stair area.
I suggest that you not plan on the 2x6 T&G as you finished floor on the second floor – but rather plan on putting down carpet or hardwood on top to the T&G. We went with hardwood in our case and are very happy with it. When the T&G dries out – and it will -you will get a lot of opening between planks – almost to where the T&G is completely open. Doesn't look bad from the bottom but you will have 1/4 gaps on the second floor. (We started out planning to use the T&G as finished flooring.)
Lots more I could write – about wiring etc. but got to go for now. Get back if you want to hear more tales. Also plan on things taking a long time and plan on almost all of the contractors / crafts not having a clue of how to work with a timber frame. If its not stick framing many will just walk away. If it's not planned, in advance you will have a real problem with electrical and plumbing. But don't quit -- it make a great home.
deblacksmith