Laying out a constantly changing curve
I’m no framer, although I do know how to build boats.
Knowing my love for boatbuilding, the architects have come
up with a very beautiful design involving constantly changing
curves for our owner-built home project. One is a gentle
50 foot long elliptical curve on an exterior wall; the other
curve is a cam-shaped footprint for a turret.
Now how do you lay out the foundation? (I’ve searched and read
other threads here about building curved walls on the deck)
In boatbuilding this is done on a smooth, whitewashed lofting
floor in the attic of your shed, using X and Y coordinates,
nails to mark off the spots, and a long batten to create the
curve, which you then draw in with a pencil.
The only suggestion I’ve heard is that you’d have to create
a platform out there in the mud on the building site, draw
in your curve, then transfer it to the footings somehow (which
presumably you have already poured in roughly the right place)
Here are some rough 3Ds of this very preliminary design:
Replies
Those are top secret layout tricks, and very hard to explain.
Use concrete pins in the dirt, instead of nails in the floor.
Strings on batt boards make your x and y grid.
Long tape spinning on top of pin could make arcs
You could also hire a company that has "total station" to do this for you.
I hope Chuck Norris never potato sacks me!!!!
bstcrpntr --- I hope to grow into this name.
>>Those are top secret layout tricks, and very hard to explain.That's what I was afraid of.
A cam is two circles whose centerpoints are seperated by radius A - radius B + Cam lift. Then draw tangenital lines to connect the two circumferences.
I should have said that it's a cam-like blob footprint with
constantly changing curves.I think that I will have to put my foot down with the architect
and insist that he give me regular geometrical shapes that
do not need battens to create. Make things a lot simpler.
talking.... the architect can plot a grid for you with as many points as any form company can hit.. his lofting battens are in his cad program ( splines )
the real question is what is the form company going to use to form it.. segments or custom curved panels..
my guess is that they will use segments ( 1 foot panels, 2 foot panels , whatever )
curves and changing curves are done all the time, but most projects do not have the budget to do it
Mike Smith Rhode Island : Design / Build / Repair / Restore
Being a surveyor and having laid out numerous parabolic and spiral curves, the first requirement is a good reference point.
Have the architect run a coordinate system on the face of the finished curved foundation, preferably on 1' chords, as the tighter the curve, the more error you may have when you lay it out. Specifically you need coords at the PC (point of curvature), PCC (point of compound curvature), and/or the PSC (point of spiral curvature). These will be your control points.
Have 2 good reference lines perpendicular to one another, and have the architect provide stationing or distances along these lines perpencidular to the above mentioned control points, with distances to the points. This allows the surveyors or slab crew to set up an instrument and ninety in the control points. By two-taping or turning angles provided by inversing between the set-up points you may set every point needed along the curves, and the offsets where needed. A layout on a 1' grid for double checking would be advisable for a quick visiual.
The architect should supply a coordinate sheet with all points inversed from both reference lines.
I am not sure I understand the language you use here, but I understand
how to blow up the lines from the print, provided I have a table of
offsets.So if I understand this right, I have to go through the process twice,
once to get the footings, roughly, and then once more very precisely
the get the line on the footings the forms should follow. I am going to
have to drive concrete nails down into the footings and then bend my
batten around those and try to scribe my fair line on the rough cement, is that right?In answer to Mike's question, if we do this at all it, we will probably
have to do the foundation ourselves, for the cost reason mentioned.
I understand that some ICFs can be used in a radiused application, so maybe we'd use ICFs. It might make life easier if I could build it in segments.
In the curved work I've done, the footings were always poured larger than the curved portion of the foundation to make layout easier and have room to tie the steel. These were usually curved RE walls with concrete foundations, and concrete holding tanks for water treatment plants.
The layout can also be accomplished easier if the architect provides easily constructed radius points that correspond to the face of the finished foundation. It would be easier to set the radius points, strike arcs, then connect the arcs together to provide the location of your battens. You could also use the "garden hose" method. Just a 100' of hose and you can lay out any curve needed as long as you have a few dimensions on the prints.
Seems to me that whoever produced the prints should provide the needed layout information. If not, it may reduce your liability to call a surveyor in for an opinion. You can save a whole lot of time that way.
So if I understand this right, I have to go through the process twice,once to get the footings, roughly, and then once more very preciselythe get the line on the footings the forms should follow. I am going tohave to drive concrete nails down into the footings and then bend mybatten around those and try to scribe my fair line on the rough cement, is that right?
That's what I did. Your flickr link didn't work well for me so I don't know how tight your curve is. Here's our place. Front and rear walls had to have the same curve for the bar joists to work. Not particularly complicated. My first effort at housebuilding, and concrete forming for that matter.PAHS Designer/Builder- Bury it!
Looks good. I feel encouraged and emboldened.
Fortunately I only have to do concrete stem walls
18 inches in height.
18 inches in height.
That makes it very simple. I'm 16 ft tall (x52'). I like the venerable snap tie system. Not fast, but the hardware's inexpensive and very easy to use. Bending the plywood (CDX in my case) is the most difficult part.
I cut curved walers with my bandsaw but a saber saw would be adequate.
One problem I had (and you don't want) was starting second wall forming at the end of the wall. By the time I got to the other end, the inside/outside differing radii made the snap tie holes extremely out of alignment. Starting in the center of the curve splits the difference in both directions. Snap ties are forgiving, but there's a limit. Tighter curve would be more pronounced.
Of course, I think you'd have a better house if you continued those concrete walls all the way up. Then you can easily get the arch of your choice for windows and doors. You obviously like curves, no reason to stop with the walls. Continue the theme with fenestrations. Just know that you signed up for some millwork. The home center probably won't have what you need in stock. PAHS Designer/Builder- Bury it!
Wow, that kitchen door is way over the top. You are doing
some high end work there. I am going to shoot the architects if they start suggesting rounded doors and windows, too.Looks like I am going to have to buy a bandsaw for this project,
or at least a Festool.After I get the walers done, I was thinking that maybe I could get
around the bent plywood thing by using sawn lumber, such as 1x4
placed vertically. Maybe rough cut in random widths to create some
visual appeal.On the subject of walers. Is it possible to cut them out of very thick plywood, such as the 1 1/8 thick stuff used for subfloors, rather than sawing up a bunch of 2x12s? At the same time, is thick plywood an acceptable substitute for 2x stock in stick framing a curved bearing wall (it seems like it wouldn't hold nails as well)?It would be nice if I could build this project in concrete, that's
what everybody says. Unfortunately, the plot is on terraced hillside
with fill that is 30 feet deep in places. So, even to build a
wood frame structure I need to drive 4 inch steel pipe screw type pilings. For concrete I need 12 inch cement piles.That cement pile driver is a very substantial piece of heavy equipment, and it would require a gigantic crane to lift it up onto my terrace. The 4 inch pile screwer machine is relatively petite, so it is easy to get it to the site.
Wow, congrats Pop.
Yup, had some fun here. And dislike small doors. The inner one's 4' wide, nice to have elbow room when you're hauling groceries. But it's all in scale, including the curves. You noticed the windows in the opposite wall? Adding a curve or two to dress up an otherwise rectilinear box doesn't favorably impress me. Kinda like that plan Boss is working on with a couple of arch-topped windows. The point misses me.
Go with your flow, you'll enjoy it.
Sounds like your site is tenuous at best. 30' of fill? Yikes! And you're saying it wasn't compacted. Are you supposed to float a house on it, or build something that'll just bend a lot? Pretty sure I'd be looking into post-tensioned floating slab if there's anybody doing that. Or... how about a yurt? Does traditional Japanese (temple) joinery still exist? Practitioners, that is.
I love my bandsaw, the only must-move stationary tool I had in Denver. It's done a lot of slicing for bent laminations, which is a very simple technique. Those doors, for instance, only took 2 bending forms (L shaped oak screwed to a sheet of form ply), including for the casing. Bent laminations are incredibly strong and stiff.
Plywood walers would be fine so long as they didn't delaminate. I've got my own (hard) woodlot so no problem with lumber which is much cheaper than ply. I've used vertical boards (differing widths and thicknesses) in formwork before, but it was to immitate a board fence. With colored concrete, at 10', few could tell. I used plywood for holding the whole thing together and the client stuck the boards inside the forms, tapered with a nailer at the top edge. What you're proposing sounds floppy, the last thing you want when you're placing concrete. Quite certain I'd be bending the plywood. If the curve's tight, multiple layers of thin ply would work. When I suggested snap ties I hadn't looked at your location and took the normal North American assumption.
Nails I don't know much about, have little use for them. It sounds like you're planning a North American style stick built house. Then the nails simply hold the plates by going into the studs. BTW, I've got paulonia almost ready to harvest. Don't really understand the attraction. Just tradition?
You're planning a stem wall on piers? I helped with an 11 acre project built that way 100 yrs ago in an area with bentonite problems. Last time I visited it was standing. An engineer could determine how much weight the piers could support. That would be the only problem with cast full-height walls, weight. But we drilled holes to cast the piers. Pile driver? 4" screwer machine? You lost me, but I'm not a GC.
Sounds like you're off on an adventure.PAHS Designer/Builder- Bury it!
>>Sounds like your site is tenuous at best. 30' of fill? Yikes!Dunno if it was compacted or not, but a major GC looked at the soil numbers and said that they could guarantee the foundation no sweat
if pilings were used. This is even though we are next to an active faultline.This sort of site is really typical, since there's not a lot of good flat land and they have to terrace the (formerly unbuildable) hillsides.I am not a GC or an engineer, so I just know what they tell me. For concrete, we need either cement milk or the big concrete pilings, and that equipment is a real accessibility problem.The metal pilings (is that the right term?) go down like an oil drilling bit. The first one has an auger on the end, and the successive sections screw into that.>>Bent laminations are incredibly strong and stiff.They build domed stadiums here out of the stuff.>>I've used vertical boards (differing widths and thicknesses) in formwork before, but it was to immitate a board fence.Isn't this the way they did formwork before there was plywood?I have another idea, though. USG Duracrete panels, which are wildly popular here, for some reason. Use those instead of plywood, since they are designed for bending but still have maintain structural strength.BTW I took a look at your webpage. That house you've built is insane! I love it. I actually wanted to build a roof like that, so I could do gardening up there. Grow daikon, etc. But I need either heavy steel or concrete to do a roof like that.My architects are on board with the idea of rooftop greening though, but I think it will have to be one of the lightweight types.They also did a house with copper cladding on the outside--it's pretty unusual. http://www.ftarchitecture.com/portfolio/copper-house/Do you know of the copper is still affordable? I have been looking at painted galvalume tambour ridge siding, but copper would be kinda cool.>>I've got paulonia almost ready to harvest. Don't really understand the attraction.Obviously you are a woodworker who knows a thing or two. Paulownia is the perfect thing for making closet guts and drawers, especially in a climate like yours, which is very similar to Japan's. Without aggressive climate control, there are severe problems with moisture inside closets and dressers. Paulownia is a natural means of climate control for these spaces, soaking up excess moisture in summer and giving it off in the winter. The same is true for wattle-and-daub walls, but I digress...It is also a very workable wood. It's possible to make absolutely exquisite cabinetry out of it with just planes and scrapers, and no sanding or finishing necessary. It also carves well. I am not sure that it's on a par with something like limewood, but we do use it for carving in certain applications, since it's so incredibly light.
>>Bent laminations are incredibly strong and stiff.
They build domed stadiums here out of the stuff.
Clearly, thin shell concrete outperforms. 1950's technology that I'm exploring, ala Felix Candela. Now commonly used for large commercial spaces like airports. Differing, my interest is solely below grade, which solves the common problems.
That house you've built is insane! I love it. I actually wanted to build a roof like that, so I could do gardening up there. Grow daikon, etc. But I need either heavy steel or concrete to do a roof like that.
Thanks. This is standard commercial construction, beefed up for the earth load. Very inexpensive with the lightweight steel. The reason for the earth load: it's our sole heating/cooling system (passive annual heat storage, PAHS). Works admirably. I've been proselytizing for steel bar joist use on this list for quite awhile. Generally cheaper than wood. The spans are amazing.
http://www.ftarchitecture.com/portfolio/copper-house/
Didn't load well for me. I'll try again tomorrow. Copper was, and probably still is, the cheapest (lifespan) siding I've found. Pre-formed copper siding is incredibly expensive here. These were 3'x10' sheets, normally sold for roofing. CorTen was the other siding I considered. As you read, I'm sold on zero maintenance. Copper works, extremely well. Used it on the roof of my lumber shed. Do it once, enjoy it forever.
Thanks for the heads up on paulownia. Summer humidity is a major issue here. Are you saying there's no mold problem with its soaking up summer moisture? Your thread, but I'd appreciate digression. I'll do some testing. You're right, weighs next to nothing, very soft. To me, only acceptable as a secondary wood, as you mentioned. I was under the impression it was a primary furniture wood there, occasioning the very high prices paid here. My most valuable timber.
My vocation is furniture making, currently on hiatus.
PAHS Designer/Builder- Bury it!
>>Clearly, thin shell concrete outperforms. Lotta cement buildings here but no thin shell as far
as I can see. Cement has actually fallen out of favor since
the mid-'90s, along with the widely publicized failures of
buildings in the Kobe quake. Engineered wood, OTOH is
expanding like crazy, both on the residential level and the
commercial. They have even certified it for use in building
skyscrapers.One problem with concrete in this climate is that people seem
unable to take care of it, inside or outside, and the result
is a mess. People hate it.>>I've been proselytizing for steel bar joist use on this list for quite awhile. Generally cheaper than wood. The spans are amazing.There's a lightweight version of the steel bar joist that can be
used with stick framing, isn't there?>>These were 3'x10' sheets, normally sold for roofing.
CorTen was the other siding I considered. As you read, I'm sold
on zero maintenance. Copper works, extremely well. Used it on
the roof of my lumber shed. Do it once, enjoy it forever. IMO CorTen has the risk of creating rust stains on masonry
downstream, but otherwise it's pretty cool. You see a lot of
copper here in high-end traditional roofs. We have one here
that is so old it's got holes in it from water dripping in
the same spot from above (acid rain?)The zero maintenance solution reached here is an AAC panel
with a ceramic or nanotechnology coating on the outside. If
it ever gets grimy, you just hose it down. Keeping the caulking
joints up to date is another matter, though. And I don't like
the looks of these over-engineered products. Give me something
that weathers gracefully like copper.>>Thanks for the heads up on paulownia. Summer humidity is a
major issue here. Are you saying there's no mold problem with
its soaking up summer moisture?We've got an old dresser in the corner, incredible humidity,
no problem with mold in the wood itself. Other wood, such a
pine, will turn orange with a bloom of disgusting stuff at
this time of year.I have a background in cabinetmaking, and I must say I was
slackjawed the first time I saw a Paulownia cabinet in real
life. I could not believe what I was seeing. These cabinets
are usually part of a traditional bride's trousseau, and are
used for storing kimonos. They can cost up to $300K.If your work is of the James Krenov type, where you can get
away with hand scraping and minimal finishing, you ought to
try it out, because I think it's a very forgiving wood.
Lotta cement buildings here but no thin shell as faras I can see. Cement has actually fallen out of favor sincethe mid-'90s, along with the widely publicized failures of buildings in the Kobe quake.
As you know, reinforced concrete's only strong if the concrete stays with the reinforcing. Shake it, there's a problem. Thin shell, depending on how you reinforce it doesn't have that problem. Witness concrete boats, ready for wave pounding. We don't have much earthquake risk here. Two since we've been in Va. One got me out of the house fast (with 200 tons overhead). No damage.
The problems with original thin shell had to do with overheating and cracking. Plus the problem with what to use for waterproofing. And how to replace it when it fails. Going below grade can solve those easily. Which has nothing to do with your project...
Bar joists are designed for the loads encountered, light to heavy. None are particularly weighty, or expensive, here. A major factor in the economics of what I've built. Spans are my interest.
If your work is of the James Krenov type, where you can get away with hand scraping and minimal finishing, you ought to try it out, because I think it's a very forgiving wood.
I broke bread with Krenov several times. My mentor was an old friend of his. Pretty sure he wouldn't approve much that I've done with wood, but Krenov was a strong influence. Your metaphor is apt.
There are several ~14" wide 6/4 paulownia boards in my lumber shed. My preferred sawyer left them and has been unhappy that I haven't turned them into anything. I was aware of the traditional Japanese use (occasioning the high log prices here), but didn't see the attraction compared with my (traditional) domestic choices. The mold issue is interesting. We control rh very carefully so don't have a problem, but that's unusual here. I'll test. I'm sure you know that wood taking on (summer) moisture and giving it off during low humidity times is the nature of all wood. Speed depends on the finish.
Spent time this week with old friends, 19th c. English furniture imported in the last decade. Museum quality, owner has great faith in me (I'm too polite to argue <VBG> ). Pretty stable now but experienced great movement while acclimating. Mostly I've worked my way out of employment there. Partly with harping about rh control, finally realized. Yesterday had to retrace finding the hidden caches in 2 pieces, including one technique new to me.
Tools of my trade are mostly Japanese. Laminated chisels and those wonderful saws. My life got immensely easier when they were introduced. Makes dealing with wayward veneers a pleasure and me appearing to be a hero. That's what you want from tools, making you look good.
BTW, our place was designed to be my future furniture shop once I built what we really wanted to live in. Finances are arranged, it's out of the ground. The reason I wanted the curves here, both walls and fenestrations, in addition to satisfying my esthetics (important as that is) but also as a sales pitch. The plan was for the client to drive up our long driveway to the wonderful site on top of the mountain, visit me in my somewhat extravagant shop, and open the checkbook. Plan's changed, but it's working.
Here's something I offered to a prospective (bed) client with whom I've had design difficulties. It was well-received. We're still working. Not exactly Krenov.
Or not. Prospero won't accept my upload tonight. Grrrrrrrrrrrrrrrr..........
PAHS Designer/Builder- Bury it!
>I'm sure you know that wood taking on (summer) moisture and giving it >off during low humidity times is the nature of all wood. Speed >depends on the finish.Having grown up out in the Rockies, where it's usually bone dry, I wasn't prepared for the seasonal swings in humidity that we get here, the effects on wood. I also had never seen green lumber before, so I was in for a big learning experience.>Pretty stable now but experienced great movement while acclimating. This is one area that the Japanese understand. Yamaha pianos, for instance, are famous for being able to move accross climates without going to hell.>Tools of my trade are mostly Japanese. Laminated chisels and those >wonderful saws. My life got immensely easier when they were >introduced. Yep, some very good tools. The high end toolmakers are these days being kept alive by demand from the German craftsman market, mostly, and also by Americans like yourself, to a lesser extent. I have some planes and some decent old handsaws. I usually like to use a disposable backsaw with the fine tooth bamboo cutting blade, which for some reason, never loses a tooth, unlike the normal Gyokucho disposable backsaws.Now back to my curves.I made a visit to the local mom and pop lumberyard today, where I determined that I would be able to use his bandsaw for cutting the mudsill. This guy has a monster bandsaw, an industrial Ryobi with a four inch resawing blade on it. I am assured that there will be absolutely no problem cutting my four by six mudsill stock to the curve required with this beast. Tight curves are another matter. One thing that's different about Japan is that the lumberyard has a whole set of stationary machines that are available for tradesmen to use on the spot, or that you can ask them to use in preparing your order (I prefer to cut it myself, though). It's not uncommon to see a carpenter cutting out an entire job, mortise and tenons and all, right there on the floor at the lumberyard. Guy will be in working in there for a week or more.
We moved here from Denver, where I occasionally was able to buy green hardwoods from the midwest. Air-drying works like a dream there. Being part of a good-sized woodworking community has its advantages.
The first dining table I shipped to New Jersey (from Denver) had me a little worried. All went well.
That's amazing about Japanese lumberyards. Talk about customer service.... doesn't get much better than that. The few yards here who actually have tools are generally afraid to use them. In fact, my larger stationary tools came from one that decided it was a bad idea to have them around.
Have fun!PAHS Designer/Builder- Bury it!
>green hardwoods from the midwest. Air-drying works like a dream there. I'll tell you a little trick. If you ever get stuck with green lumber that you need soon, no time to air dry it, you can make a very effective kiln with a few sheets of rigid insulation, some duct tape, and a heat source--I use a kerosene fan heater.>That's amazing about Japanese lumberyards. Talk about customer service.... doesn't get much better than that. It's an age old practice. Probably dying out as the old ways of doing
business in construction are rapidly changing. I wish that customer service included a boom truck, though...>The few yards here who actually have tools are generally afraid to use >them. In fact, my larger stationary tools came from one that decided >it was a bad idea to have them around.In the US it would be insurance issues. Here they don't worry about liability insurance, since nobody sues.Bigger lumberyards here in Kyoto will have bandsaws capable of taking on some prime Oregon old growth timber, and it's not uncommon to see them have a stock of hefty sawlogs. You want a particular thing, you go in and have it sawn up while you wait.
stuck with green lumber that you need soon
Thanks for the thought, but highly unlikely. I'm familiar with JIT practice and don't find an application. Certainly when I was buying green lumber, it was with a distant use in mind, usually a hope rather than a commission.
Part of my reason to move to Virginia was the availability of my own green lumber, a sizeable private woodlot. It's an incredible luxury. I keep several thousand board feet on hand, saw whatever I think I might possibly want. Haven't yet completed my lumber drying/storage shed, but it incorporates a good-sized solar kiln. Not that kiln-dried is necessary here, but I'm interested in selling boards rather than logs. Kiln-drying is a requisite for that here.
Part of what I find invaluable about this forum is learning about practices that would be highly unusual here. Your description of Japanese lumber yard SOPs (even if in decline) are amazing. You apparently appreciate the difference.
Which comes full circle to another question, certainly off-topic. How does "Law/Legal Services" incorporate your obvious understanding and affinity for what we've been discussing? Not to mention your participation in constructing a free-standing house? You rue the lack of a boom-truck, indicating experience there. Apparently not your first time.
If overly intrusive, feel free to say so, but I'm sure I'm not the only one here who looked at your profile and wondered...
Either way, thanks for the thumbnail picture of lumber yards there. Something for me to consider. PAHS Designer/Builder- Bury it!
>availability of my own green lumber, a sizeable private woodlot. It's an incredible luxury. I suppose you've got lots of oak, ash, hickory, walnut etc. It is quite a luxury.>Japanese lumber yard SOPs (even if in decline) are amazing.When I was in there the other day I asked for some oak and I was shown a bunch of fresh cut 36 inch slabs leaning against the wall. Price for those will probably be over $1000 each--furniture makers will do that George Nakashima thing with them. This is very typical. He's got a whole stack of very black wood in the back that's been drying for almost 20 years, quite a bit more expensive still.>understanding and affinity for what we've been discussing?If you want to know about my background. Briefly, I've got construction in the bloodlines, and have done my two years before the mast. My skillset is more profitably employed working with words and concepts, unfortunately (because there are lots of days I wish I were knee deep in shavings). Since coming over here, I've had quite a lot of hands on experience working on old Japanese houses, on a weekend basis, and I also mess around with old boats and carve masks.
I don't know how much you want to go into this, but I used to drive a few of those helical piles (first section an auger, then 1 1/2" square stock sections until you get to desired torque). The torque motor we used to drive them really wasn't that big- a couple hundred pounds, and it fit on a fairly small rubber tracked excavator (we usually used a kubota kx-91). That's a very versatile machine, and I would be suprised if a good operator couldn't get it where you need it without too much trouble.
Obviously, there are a lot of other factors in the concrete vs stick decision, but I wouldn't take it for granted that the pilings are the big sticking point. I've sent those things down 40 feet or so, just keep adding sections every 5 minutes or so.zak
"so it goes"
This is what I am talking about, what they call the "spiral fin"
technique.http://www.daiwa-shisui.co.jp/hp/kisohokyou/koukan/koukn-sekou.htm
That's fairly similar to what I've used, except that yours is based on a round pipe.
http://www.joslynmfg.com/MacLean-Dixie.aspx is what I've used.zak
"so it goes"
>>Continue the theme with fenestrations. Just know that you signed up for some millwork.This is modern architecture, so I doubt the architects will be specifying much trim or Palladian windows. Bent glass maybe, or out of square windows.Which is all well and good. I still remember the difficulty I had, back when I was a wee lad, installing mahogany crown molding on a 3 foot diameter cement column in an office building. No thank you, ma'am.
Gonna be an interesting project. Don't forget photos for us.PAHS Designer/Builder- Bury it!
Once upon a time, I was surprised, when I asked the Architect for more details to plot a house with lots of angles and offsets--and he sends out triangulating dimensions to the corners and offsets from the survey stakes and property lines.
They've got the technology if they know how to use it ---or wish to share it
The grid sounds like it would give you what you need----but you ARE going to be out there in the mud----
Just remember--this is the closest we guys get to giving birth--
good phrase... i'll use that one again
<<<this is the closest we guys get to giving birth->>>Mike Smith Rhode Island : Design / Build / Repair / Restore
Yes, tha's a good phrase.Speaking of which, I just got back from the
hospital, where I helped out in the delivery of
a healthy 3500 gram girl.
Just a slight hijack
Congratulations on the new baby girl!
Doug
Edited 6/25/2006 9:48 am ET by DougU
Don't know if this help you, but for laying out curves I use 1/2" pvc water lines. rigid enough to maintain shape, flexible enough to bend.
PVC water lines? Thank you, that's a really good suggestion.(I understand lengths of PVC water pipe are also being used to discipline children in the US these days--versatile stuff.)
I've been chewing on your question on and off since yesterday and know far less about forming curved walls than the crews that do it all the time, but your problem seems quite doable.
Having built smaller scale projections with ICFs on a full ICF house, I'd rule them out since you are limited to something that looks much less than smooth when following curves.
For instance, ARXX block has the nylon reinforcement, that holds the sides together, every 8". Even if you use a 12" section to retain a reinforcement in the center of the section, the edges that need to be joined need significant wood/tape/foam glue reinforcement to hold together and remain plumb. To hold it together would require more wood than simply forming with plywood from the get go.
ARXX does have a variable angle corner that swivels and remains more structural at the joints, but it's quite a bit longer than you would need.
For simple curves in short walls we have used multiple plys of thinner plywood, with staggered joints and all screwed together. 3/8" cdx ripped to 18" or whatever your wall height is, would seem to bend quite easily. Perhaps 1/4" if needed.
Along the top edge additional layers 4" wide keep the form straight. Ripped to 4", 3/4" ply bends quite well.
Along the bottom edge of the form, the clips that are about an inch wide, sit flat on the footer with a nail in the center to hold it, and span across from one form board to the other are easy to set and would keep the curve true.
If it were extremely important to keep an exact curve, I'd laminate a few layers of cdx plywood cut in 6" strips for the bottom and 12" wide on top to match the outside curve of the forms. Those bottom layers could be quickly screwed down with Tapcon screws and the thinner plywood layers would be screwed onto the curves top and bottom. Then there's a bunch of lumber to further firm up the forms and tie the tops together.
Try to anticipate how the forms will deform once mud is placed and make allowances, since it's many times harder to plumb or move a curved form once it's out of shape.
Overbuilding the forms might look like a waste of lumber, but it's a lot easier than fitting your cam to a lopsided wall.
In the end you'll have a pile of oddly shaped plywood scrap since it's a pain to remove all the concrete encrusted screws peppered throughout the plywood, but it could be worthwhile to salvage the ply for future curves. Putting the screws in with some sort of forethought makes salvage much easier. Also, consider washing the outside of the forms after the pour to help find the many screwheads.
As for framing curves, it seems the most popular to use two layers of 3/4" pt cdx ply as the bottom plate, multiple layers of 3/4" cdx ply for the top plate, and closely spaced studs to smooth out the curve. It might take a few sheets of thinner sheathing to properly smooth the exterior curve. I'd want approval for all this from the building department and architect before framing starts in case your inspector has some hang up on these things.
There was a FHB article a while back that spells out the framing issues, complete with header details that might help if you haven't seen it before.
For strange shapes, I like to have the person drafting the plans produce a separate sheet with xy coordinates every few feet for the shape in question, in addition to clearly labeling any known diameters, radii, or other geometric whatnot.
Good building.
>>ARXX does have a variable angle cornerI understood that Nudura had some way of curving their blocks to custom order. Are you familiar with their RAD-x series of 96 by 18 custom blocks (product catalog, page 2)? It seems I could do my entire outer wall with, let's see, about half a dozen blocks.>>If it were extremely important to keep an exact curve, I'd laminate a few layers of cdx plywood cut in 6" strips for the bottom and 12" wide on top to match the outside curve of the forms. Those bottom layers could be quickly screwed down with Tapcon screws and the thinner plywood layers would be screwed onto the curves top and bottom. So, if I understand this right, the top of the form flares out on both sides, because it's reinforced by two 12 inch curving strips of ply? So the entire width at the top of the form would be 12 + width of cement + 12?>>As for framing curves, it seems the most popular to use two layers of 3/4" pt cdx ply as the bottom plate, multiple layers of 3/4" cdx ply for the top plate, and closely spaced studs to smooth out the curve. It might take a few sheets of thinner sheathing to properly smooth the exterior curve. I'd want approval for all this from the building department and architect before framing starts in case your inspector has some hang up on these things.We have the most beautiful structural plywood in the world, absolutely perfect stuff, so good you want to make cabinets out of it. (actually, I did make a kitchen out of it). Nevertheless, I'd be worried about screws or nails pulling out in a shear wall. The nail pitch I have to follow is pretty tight. I wonder if they have lumber core with waterproof glues.As for the sheathing, I mentioned this before, but the USG Duracrete product is what they use here for radius walls. It's a bendable structural cement panel that apparently is just the bees knees. Architect says I may be able to use this stuff instead of plywood, which would be real neat, because then I could just smear some grailcoat on the top and be done.>>There was a FHB article a while back that spells out the framing issues, complete with header details that might help if you haven't seen it before.Header's another problem. I need to get that FHB article. I saw a very slick sheet metal header product from http://www.flexc.com/ -- are you familiar with it?>>I like to have the person drafting the plans produce a separate sheet with xy coordinates every few feet for the shape in question,That's what they call a table of offsets. You can pretty much build a boat from just that. As long as you have a good batten.
I understood that Nudura had some way of curving their blocks to custom order. Are you familiar with their RAD-x series of 96 by 18 custom blocks (product catalog, page 2)? It seems I could do my entire outer wall with, let's see, about half a dozen blocks.
So, if I understand this right, the top of the form flares out on both sides, because it's reinforced by two 12 inch curving strips of ply? So the entire width at the top of the form would be 12 + width of cement + 12?
Yep. Looks funny.
>>There was a FHB article a while back that spells out the framing issues, complete with header details that might help if you haven't seen it before.
I saw a very slick sheet metal header product from http://www.flexc.com/ -- are you familiar with it?
Nope. If there were a local source for it we'd be more inclined to give it a try, but with many good ideas it's the course of least resistance to do it with wood.
There seems to be some great metal products for curves, including a curvable track that works as a curvable bottom and top plate. Used with metal studs, it just screws together. Slick.
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Your project sounds like fun.
Good building.
Is the foundation exposed? If not build fairly stright and an over hanging platform cut to the shape you need. You could also build with block and form the shape as you build, parge the finish to smooth the shape, that way you only need to form the footing to the curve.
>>Is the foundation exposed? If not build fairly stright and an over hanging platform cut to the shape you need. You could also build with block and form the shape as you build, parge the finish to smooth the shape, that way you only need to form the footing to the curve.
Yeah, I was thinking of something along those lines, sort of a way of cheating the curves. At this point we haven't figured out the finish for the foundation, but I fully expect the architects to come back with something real cute like stone veneer.But building with block here is strictly verboten.
Whats the problem with block?
I dunno. Earthquakes probably. (Are blocks used
for building in Californis?)