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Slipform Questions
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Mark,
Sounds like you found a good solution to the cost problem. Congrats on the thrifty thinking. I do have some minor concerns about the long-term durability of the glue... in other words, is the OSB going to be at risk of peeling away from the beadboard after a number of years? The R-Control panels are glued together in a large press, so there is a lot of weight to firmly press the OSB to the beadboard. Personally, I think you will be fine with your approach, especially since the panels will be locked in place by everything else-such as the interior walls that butt against it, the sheetrock that covers it, and the sheetrock on the ceiling material that butts up against it.
However, for extra insurance, you might think about some ways to permanently tie the OSB through the beadboard to the concrete. For example, if you are using wire ties for the formwork the way it is demonstrated in the video, then you might leave some or all of the wire ties in place. Sheetrock would easily lay right over small diameter wires (like tie wire), or you might look at making a shallow groove in the OSB for thicker wires. I would recommend a medium-sized wire, since tie wire isn't very strong, and could also rust through easily where it enters the concrete. The thicker, stiff wire I showed for doing a concrete pour in the video would be excessive for stonework and wouldn't lay flat, so look for something in between.
Sincerely,
Thomas J. Elpel
How should the holes be spaced to anchor beadboard panels to the concrete?
Dear Mr. Elpel,Mark,
I don't know what the best spacing would be, but I think you have the right idea to predrill the holes in an assembly-line process. It is too easy to forget about it later on. The loss in R-value should be minimal, so I wouldn't worry about that part too much. I might put three holes across the panels horizontally, such that two were about six inches from the edges and the third was in the middle (sixteen inches apart from the others). Vertically, I might do a similar pattern, starting about six inches from the edge and spacing the rest sixteen inches apart. This number of holes might be overkill, but you can be certain the panel won't come off the wall. While you are doing some assembly line work, you might also want to predrill the panels for your form wires to go through.
Sincerely,
Thomas J. Elpel
How should I build the window frames in a slipform wall?
Dear Mr. Elpel,Mark,
For the window framing, we've used 2 x lumber in the past, but I really liked the method we used in the video, where we built the frames out of scrap beadboard panels. In fact, you could recycle the scraps cut out from the window and door openings to make the window and door framing.
The one thing I might do different on a house would be to push the beadboard panels all the way to the outside of the wall and stucco the edge to make a six-inch wide "picture frame" around each window, instead of bringing the stonework all the way in as we did for the workshop in the video. Optionally, the beadboard could be trimmed down to make a more narrow frame.
Sincerely,
Thomas J. Elpel
How much concrete and stone goes into a slipform stone wall?
Hello Thomas,
I purchased you book sometime back and enjoy reading it over and over again. My wife Cozy and I plan on building a home in the near future. I do have a question though. The question is, in a 10 foot square section of a home how many stones have you used on average? And how much concrete have you used on average within that 10 foot square section?
Please note I plan on building our home having stone on the inside and outside. My concern is the cost of concrete these days and the amount of concrete that I will need to construct the home. As I suspect, you will agree that it is difficult to determine the amount of concrete when not knowing the exact sizes of each stone. To date, my plans are to have a 25 inch wall. This includes the 6 inch (5 1/2) beadboard, stone on each side, rebar and concrete. I believe you mentioned having a 9 inch spacer on each side. If so, that would put me at approximately 25 inches total width of wall? Hence, I think you can see the dilema in not knowing that amount of concrete needed and it's cost.
Any help would be greatly appreciated.
Thanks,
John
John,
Thanks for writing. Our double stone walls with insulation are typically about 7-1/2 inches thick for each stone wall, plus the
insulation. A normal 9 inch wall is typically half stone, half concrete. The 7-1/2 inch walls are probably 2/3 stone, 1/3 concrete, with rebar pushed through the insulation to connect the two walls. I'm not sure how much cement that works out to. However, if you are close
to a source of fly-ash, a waste product from coal-fired power plants, you can substitute about 30% fly-ash for cement. The fly-ash is a waste product with cement-like properties, often disposed of in landfills. I found a local source for fly-ash at 2/3 the the cost of
cement, so there was a small saving there. You might also consider doing a double stone wall up to the windows, then switching over to strawbale construction for the rest, which would be faster and cheaper. At least keep your plans flexible, so you can switch over if
you decide to.
In regards to stone-size, I like to use the largest rocks as I can, that are +/- half the thickness of a 9 inch wall or 2/3 the thickness of a
7-1/2 inch wall. However, we did build one house with mostly baseball- to softball-sized rocks. That added a lot of extra work, though it looks good.
I hope this helps. Be sure to take lots of pictures of your project, and good luck with it.
Sincerely,
Thomas J. Elpel
Is full-strength concrete required for slipform stone masonry?
Greetings, Tom!
I imagine you get your share of questions due to your wonderful book, which is splayed out on my desk alongside the Schwenkes, Nearings, Kohlers, and Stanleys of the slip-form world. I'm in the process of building an "embiggened" version Joe Kohler's beautiful cape over here in Worcester, Vermont, and have got my poor brain hung up on the question of concrete. I've been using Kohler's "mortarcrete" recipe (very similar to the 5:1 recipe recommended in your book) for the small bit of below-grade work I've done to date - less than one full form around the whole perimeter of the house, so far - and I've been reading and re-reading my whole slip-form collection at every step, matching the actual DOING with the reading. Here's where I'm stuck:
The early folks to the technique, Flagg and the Nearings (I've left my copy of Schwenke at work) advocate a much lower ratio of cement to aggregate than you and your more modern confederates, with Flagg using a 15:1 ratio and the nearings using a 9:1 ratio. Given that:
1) Their buildings are still in use, and;
2) A bag of cement is equal in value to a truckload of aggregate,
I can't help but want to stretch things out a bit. Could you give me any info that will set me right before I make a mistake?
Many grateful thanks,
-Rick Young
Rick,
Sounds like you are started on a great adventure! The 5:1 recipe we use is approximately the industry standard for quality concrete. (We use either 3 sand, 2 gravel, and 1 cement or 2.5 sand, 2.5 gravel, and 1 cement.) Ideally, your concrete should be made up of big aggregate, with little aggregate and sand filling the spaces between the gravel, and cement coating and filling spaces between those particles. The better the quality of the concrete the stronger and the tighter (more impervious to moisture) it will be. Keep in mind that sand has much more surface area than gravel. Using a higher proportion of sand implies calling for more cement.
Also keep in mind that the mix is really only half of the strength. Getting the mortar to settle in nicely, without honeycombing, is equally important to making strong concrete. That can be a challenge in slipforming. Be sure to agitate the mortar thoroughly with a rubber glove as you pour it.
I think it is important to shoot for good quality concrete, recognizing that real world circumstances dictate that you will probably end up with something less strong, but strong enough. My early stonework was probably closer to 9:1. However, we are in a seismically active area, being not far from our neighborhood supervolcano, a.k.a. Yellowstone National Park. These days, I shoot for the 5:1 ratio, preferably substituting fly ash for some of the cement, at least on the bigger projects.
You might research the feasibility of getting a discount if you order enough cement for your entire project (or slightly less), and have it shipped in on pallets. Optionally, be sure to ask about broken bags at building supply stores that sell cement. They may sell those bags for a little less. Also check Habitat for Humanity Restores, or other secondhand building supply stores, for a possible discount on cement.
I recently built a cinderblock garden bed using free cement, in this case, the leftovers from a neighbor who build a house many, many years ago. Much of the cement was clumpy, but there was enough decent cement left that I was able to use it. I did double the quantity on some of the batches, where the quality was marginal.
You might also research lime-based cements, which absorb carbon dioxide from the air and get harder very slowly, over decades or centuries. I'm not sure if you could substitute the cheaper lime for some of the cement, to get a product that would harden quickly and continue to harden over the long-haul, but it might be worth investigating.
I hope this helps! Please keep me posted on your progress.
Sincerely,
Thomas J. Elpel
Can we slipform a veneer of stone against our house upon an angle bracket?
Hi,
I recently purchased your Living Homes book and have found that I agree with nearly all of the things you say. ( I would say all, but I don't agree with anyone that much) My husband (he is much more conventional than I am) and I are planning to build a new house this year. I have managed to talk him into building to last, instead of putting a double-wide on a basement.
We are planning to use the foam concrete forms for the basement and walls, he thinks that vinyl siding is the way to go, but I would like to use field stone on the outside of the walls.
My question is this; could we use the slipform method and tie into the existing wall with angle brackets? I think a stone house would look absolutely wonderful, and I don't want to mess with replacing the siding that blows off. Please let me know what you think, and thank you for taking the time to answer.
Karen
Karen,
The foam concrete forms, though pricey, are a really nice way to go, and quite energy efficient. Yes, you can bolt a heavy piece of angle iron to the wall and go up on top of that with a veneer of stonework. You don't need forms for it, just some flat rocks 3 to 4 inches thick, plus some mortar, a trowel, and a little patience. It is not what I would call real stonework since it is only a veneer attached to the wall. Realistically, the vinyl siding should hold up just as well as the veneer. Not that I would choose vinyl siding for any of my projects, but yes, it is pretty good stuff, and you would be attaching it to a great wall system. Sorry, that probably isn't what you want to hear!
I guess my thought is that when you choose any one element (foam concrete forms and a basement), then it limits your choices for the next element. Hence the vinyl siding might be the better choice than attaching a veneer of stone. In other words, I wouldn't close the door just yet on other approaches besides the foam forms. Try to come at it a bit more holistically, so that you are choosing an entire package, rather than choosing the first step and forcing all subsequent decisions to fit that path. I hope that makes some sense.
If you keep the foam forms, then you might consider a blend of stonework and vinyl. For example, stonework up to the bottom of the first story windows would give the house a nice solid and natural look, while the vinyl the rest of the way up would make the house entirely conventional so that it would fit into any neighborhood.
I hope this helps... please let me know what you come up with.
Sincerely,
Thomas J. Elpel
How do I put wiring in a slipform stone wall?
HI Tom-
I purchased your Living Homes book and the accompanying video. THANKS! I have went through both of them and appreciate the detail and commonsense way in which you share your knowledge. I will be studying them both this winter to prepare for building in the spring.
I have a question: I want to put the electricity in the walls, but I'm not sure how to accomplish this. Do you use PVC pipe and put the boxes in where you design the outlets to be? I have read your excerpts from Dani Gruber. What did she do for electricity and plumbing? An architect out east, built a slipform stone home with his wife, but put a chase in the floor for his plumbing and electrical. I'm not sure if I would like the look of that, and I'm not sure how to do it, since I don't have your step by step method!!!! He also uses a different iteration of forms that you don't have to keep taking down and moving. Do you have any knowledge of this method?
I am a 48 year old woman that has dreamed and planned for 4 years to build a passive/active solar home and next year my dream will be coming true! Thanks for your excellent book and video.
Regards,
Lynda
Lynda,
Thanks for writing. Yes, you can place grey pvc conduit and boxes in the wall as you go up. There are a few things to consider here:
1) It can be difficult to think about the wiring while you are focussed on the stone masonry, especially if you are a beginning builder.
2) By the time you get the walls up and are ready to do the wiring, you may rethink where specifically you want the outlets and switches. (We had a limited amount of conduit in our walls, and ultimately mortared in the boxes on most of it.)
3) Most or all of the stonework in a stone house is usually on the outside of the house, so the wiring can be routed through insulated walls on the inside. (That is what Dani Gruber did.) If you have a large amount of
stonework on the inside, then you have to be more creative in routing your
wires.
Plumbing is somewhat of a different question, and it sounds like the architect you are referring to must have poured a masonry slab and used the chase to allow future access. You might consider another approach:
permanently imbed the drainpipes in the floor, and route your PEX potable
water through polypipe, so that you would have the option of pulling out and
replacing the PEX pipe if it became necessary 100 years from now.
As for the alternative slipform method the architect used, I'm not familiar with it, but I would be pleased to learn about it if you can get some additional information.
Good luck with your project, and please keep me informed.
Sincerely,
Thomas J. Elpel
What can you tell me about traditional Irish stone masonry?
Dear Thomas,
First I would like to thank you regarding your philophy, building knowlege, and LOVE of stone masonry.
My sister has given me land in Hillsdale, New York, next to her and I would like to build a traditional Irish Stone Cottage/farm house. My nephew Will is to be the Contractor and I will assist (he went to a Traditional Building School/VocTech) as well as a fine crew of young builders he went to school with.
In Ireland my family has a working sheep farm (400 acres on the ocean in Goleen, County Cork) which is also an old Irish farm compound. Meaning, once upon a time a couple buillt a small stone house and then kept adding other sections/houses that are connected, as well as shelter for livestock and then surrounding or connecting stone walls. I miss living in an Irish stone home where the walls are so thick that you feel like you live in a loaf of bread. Well, enough of my home sickness and on to more practical matters.
Here I am, with land and the luck that my sister and brother-in-law have 80 acres. Now, I know for a fact that nearly all the folks who built stone homes in Ireland did not have money, contractors, or Architects! Talk about limited budget, take a look at what remains of the Scalpeens from The Famine!
I will be investigating the slipform method but would like to know if you might suggest any books that cover Traditional Irish Stone masonry methods for home building.
I also will hopefully be having my roof Thatched by Patrick McGee(Master Thatcher from Ireland here in the States.) A finely thatched roof has a 75 year life span, is not flammable and just the most beautiful roof a person could have. Anyway, thanks for putting up my tome and I hope we can be in contact. I thank you in advance for answering my query.
Warmest Regards, Phoebe
Phoebe,
I would guess that traditional Irish Stone Masonry was simply stacked very carefully, using shims to fill the voids and level the stones. There was probably a crude mortar between the stones, used more to block air flow through the walls than for strength. The strength of the wall would rest entirely in the skill of laying up the stonework. In other words, I don't really know anything about traditional Irish stone masonry, except that if you needed a house and had rocks but no money, that would be the logical way to proceed.
Insulation in any northern climate would be necessary to minimize or eliminate heating costs. One technique you might consider would be to build the house out of insulation panels, as we did for the little workshop we built, then to rock up the outside without forms. The insulation panels would provide backing for the one side of the wall, while serving as a nice straight guide for the rockwork. You would be able to measure off the insulation panels when placing stones to keep the stonework nice and even. The end effect would be more of a brick-layered effect.
Notice how the stonework on that page looks different in that project than in the slipformed walls pictured on the same page. It is a stronger way of doing stonework and uses less concrete. You could still include reinforcing bar too. I realized when building our workshop that with the insulation panels for backing, this formless technique might be just as fast as the slipform method we used. I hope to try it out on a small project sometime soon.
Sincerely,
Thomas J. Elpel
Is there a way to get that "wet-look" to bring out the colors in the stones?
Hello,
I was hoping you could answer a question of mine. We had a natural river stone fireplace built in our house. Is there any way to get that "wet-look" in the stones to bring out that colour that is so obvious when wet?
Thanks for your time. Andre
Andre,
I've wondered the same thing. We use an acrylic-based floor sealer on our tile floors, which really brings out the shine, so it seems like it should do the same on stonework. There are many different brand names with different formulas, but all seem to be acrylic-based. (The tile sealer looks like milk when you pour it out then dries clear.) These products are especially intended for porous tiles like terra cotta.
I tried using an acrylic floor finish on some stonework but it turned out disappointingly dull and filmy. So, to better answer your question, I called my local brick, block and tile shop to ask for advice. They suggested the same thing: use an acrylic floor sealer (Brickyards use brand names and may not know what's inside the bottle, but they will describe it as a "water-based sealer.") So that didn't really answer the question. I guess you could try applying some acrylic-based floor finish to a small area of stonework that is not easily visible. I would leave it for a few months to see if it dulls out over time. If it looks shiny and stays shiny, then you could do the whole fireplace.
Otherwise, I am guessing that a polyurethane-based product might be more effective at creating and keeping the wet look. I don't have much firsthand experience with polyurethane, but the woodwork I have seen treated that way seems to stay beautiful forever. So you might look for a clear polyurethane that could be used on stone or masonry. And again, test a small area out-of-sight before committing to doing the whole fireplace that way.
Good Luck!
Sincerely,
Thomas J. Elpel
Is it feasible to build a three-tiered tower with slipform stone masonry?
Dear Thomas,
I have recently purchased your video and book on slipform masonry. I also have acquired some land in the Mount Shasta area, California. I have dreamt about building a mountain retreat with an old castle style . . . cheaply. Slipform sounds great and the project of a lifetime!
If you have time, a quick question. I am going to (would like to) build a small home, but much like a tower. I am attaching a picture in a word file of what I am thinking about. I will consult an achitect, and an engineer for feasibility but before I do that, I would like to know your opinion . . . can this be done with slipform?
Thank you for your thoughts
-Oliver Davidian
Oliver,
Thanks for writing and sharing a little about your Dream. Unfortunately, there is one serious obstacle to overcome to make this Dream a reality: there doesn't seem to be anything supporting the walls of the upper floors. Even if the roof of the lower levels were poured of concrete and heavily reinforced, you cannot just float the walls of the upper levels out on top of the concrete slab. The weight is immense. The upper walls must be supported all the way to the ground. Of course, the other problem is that if you brought the walls all the way down inside, then there would be no open space left inside the lower levels. Sorry I don't have better news!
Sincerely,
Thomas J. Elpel
Would it be affordable to build a stone castle?
Hi,
I came across your site just after poking through many other useless ones and thought maybe you would be the one to help me. I don't know if there's a word to describe myself, but, I'm not one for the old box-style, typical commerical homes with 2x4's and aluminum siding. I like big spaces, large rooms and such that I can explore and such. I know I'd never be a millionare so to get a big mansion in the richy part of town would be out of the question. However, I have always wondered if I could take natural materials around me and build my own monstrosty somewhere private.
I've always been partial to medieval history... Castles with towers and drawbridges and such. I live on the east coast of Newfoundland Canada just outside of St. John's, and if you know what it's like here, you'd know that it's sorta close to Ireland or Scotland; geography wise; with endless Rocky cliffs and such stretching along the coast.
What I want to do is probably outragous.. But, if I could purchase some parcel of land on top of a coastal cliff, could I afford the cost of building a substantually large Stone stucture castle?.. Do these projects get costly. Like into the $500,000 range?
Sorry if this is so vague, I'm writing this at a very late time. I have so many ideas and questions floating around in my head, and I really want to do this project with the least amount of money involved.. I really don't want to hire labours either. I'd rather build on my own, even if it would take the time to study masonry and bricklaying and whatever other course would need to be taking. And if you know what weather is like here in Newfoundland..
Can you tell me if building a structure like this can really last a long time here?
Cory
Cory,
Sounds ambitious! Our early house plans looked more like a small castle, but it evolved to become much more house-like by the time we started building.
Yes, you can build your own castle, although from your description it sounds like a lifetime project. If properly built it, would certainly last for centuries and would likely become a famous landmark, "Cory's Castle".
Cost is mostly a function of design. You can make a structure about as cheap or expensive as you want it to be. That is one of the key points in my book Living Homes, designing a building to meet your criteria for cost and energy efficiency.
I hope this helps!
Sincerely,
Thomas J. Elpel

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