Rastra or Durisol? Eco-Alternatives for Construction

lr_image_204.jpgLet me first preface this post with the following: I’m not a construction professional. I’m just a curious homeowner seeking out the best building materials for my home. With that said, I was familiar with three options in residential construction – concrete block, wood frame or the super green alternative, rammed earth.

Turns out there are new options that combine the wonderful qualities of Portland cement with recycled post-consumer plastics (Rastra) or recycled wood fibers (Durisol).


An informative, if not slightly amusing, video at the Rastra site shows the blocks being formed in giant looking muffin pans before being cooled and shipped to the building site. They are then assembled with the ease of a child connecting Lego blocks. I hope that assembly of a home could actually be as simple as they make it look – but having survived a few construction projects it is hard for me to swallow.

Both products claim superior resistance to pests, fire and noise and both look easy enough for trained hands to assemble (click, snap, glue and fill with concrete). The differences, of course, being the strength of the pre-assembled product, materials used in the mix and price.

I’ll examine all three of those issues next week. In the meantime, I’d like to hear from you. Have you used either of these products? Were you satisified? Do you have a question about the performance level? Quality? Any concerns you’d like me to try and clarify for you?

Image courtesy: Rastra

Groupon IPO: Why the company lost half of its expected value.(Innovation)(initial public offerings) go to web site groupon atlanta

The Christian Science Monitor October 24, 2011 | Barr, Alistair; Baldwin, Claire Byline: Alistair Barr and Clare Baldwin Groupon Inc plans to raise as much as $540 million in an initial public offering, less than previously planned, as the daily deals website grapples with a weak equities market, executive departures, and questions about its accounting and business model.

The company aims to sell 30 million shares, or less than 5 percent of the company, at between $16 and $18 each, according to a regulatory filing on Friday.

The midpoint would value Groupon $10.8 billion, far less than the $20 billion initially expected but still above the $6 billion that Google Inc offered to pay for the business last year.

Despite the lowered valuation, some analysts say Groupon’s shares could still struggle when they come to market in November. They point to questions over the long-term viability of a company that faces fierce competition in a business that has low barriers to entry.

The fact that Groupon has changed its accounting twice under pressure from regulators, and lost two chief operating officers this year, also has not instilled confidence.

“This offer strikes me as very, very unattractive,” said Josef Schuster, founder of Chicago-based IPO research and investment house IPOX Schuster. “I think it’s over-valued.” He said the scaling back of the IPO and the small float suggested more shares could be offloaded later. Depending on demand, the IPO will raise between $480 million and $540 million, compared with a previous target of up to $750 million.

The online daily deal industry has exploded into a multibillion-dollar business since Groupon was launched in late 2008. That growth has attracted hundreds of rivals, including giants like Google and Amazon.com Inc.

Brad Gastwirth, co-founder of ABR Investment Strategy, an independent research firm that focuses on technology and healthcare, said the lowered valuation will help the IPO, but he cited concerns about whether Groupon can diversify revenue sources and shift to higher margin products.

“There was very little investor interest in the deal at the $20 billion-plus valuation,” said Gastwirth. “While on the surface the price-to-sales multiple is getting more reasonable, there are still many questions that need to be answered before we and investors feel comfortable with this IPO.” SMALLER LOSSES Groupon is one of the most closely watched IPOs this year, as turmoil in the financial markets disrupted many share offering plans and cut the value of the few that did get done. If Groupon succeeds, it will bode well for other companies also considering going public, including social gaming company Zynga and social network Facebook.

“The market is slowly but surely reopening,” said Nasdaq head of listings Bob McCooey. “Companies including Groupon have been in wait-and-see mode for quite a while and now they are seeing an opportunity to get out and get priced, and they are taking advantage of that.” The shares are expected to trade on the Nasdaq under the symbol “GRPN.” Groupon is set to launch a roadshow next week with Chief Executive Andrew Mason, Chief Financial Officer Jason Child, and product head Jeff Holden to attract potential investors. website groupon atlanta

One of the main question marks over Groupon has been whether the company can become profitable soon. Friday’s IPO filing disclosed third-quarter results and some progress toward profitability.

On a pro forma operating basis, which excludes stock-based compensation, Groupon’s loss narrowed to $2 million in the third quarter from $62 million in the second quarter, in part because it kept a lid on marketing spending. Earlier this year, it hired Richard Williams from Amazon to head marketing.

The company said it had 30 million customers at the end of September, up from 23 million three months earlier. Customers are subscribers who have bought one of Groupon’s coupons.

Repeat customers climbed to 16 million in the third quarter from 12 million at the end of the second quarter, the company also said in its filing.

The average number of coupons sold per customer was 4.2, up about 5 percent from the previous three-month period.

Morgan Stanley, Goldman Sachs & Co and Credit Suisse are leading the underwriters on the offering.

Barr, Alistair; Baldwin, Claire


About the Author

  • please take a look at ICF’s, http://www.BuildBlock.com is my favorite, it is are a green building product that can be the basis for 18+ LEED points, they also deliver an insulation performance R Value of up to 50+, which means the heat from the sun never penetrates through the exterior wall to heat up the interior wall, I stacked a 2900 sf 2 story home that only needed a single 3 ton AC unit, a stick frame house that size would require at least 6+ tons of AC. ICF’s lower your utilities 30-70% & Insurance 20-40 percent because of 4 hour fire rating & high wind proof to 250 mph !! Good Luck !

  • please take a look at ICF’s, http://www.BuildBlock.com is my favorite, it is are a green building product that can be the basis for 18+ LEED points, they also deliver an insulation performance R Value of up to 50+, which means the heat from the sun never penetrates through the exterior wall to heat up the interior wall, I stacked a 2900 sf 2 story home that only needed a single 3 ton AC unit, a stick frame house that size would require at least 6+ tons of AC. ICF’s lower your utilities 30-70% & Insurance 20-40 percent because of 4 hour fire rating & high wind proof to 250 mph !! Good Luck !

  • i know nothing about these, i would be curious about the long term performance, particular with regards to water/moisture. what kind of stress testing have they done with water exposure, what is the longest lived installation in a wet climate so far?

  • i know nothing about these, i would be curious about the long term performance, particular with regards to water/moisture. what kind of stress testing have they done with water exposure, what is the longest lived installation in a wet climate so far?

  • Mike M

    @ John
    Good questions, I will be interested to find out what Susan thinks about durability, especially from water protection and structural corrosion. There is a green concrete company that addresses this issue by greening regular concrete. http://www.youtube.com/watch?v=Pg_z3CZbr-A

  • Mike M

    @ John
    Good questions, I will be interested to find out what Susan thinks about durability, especially from water protection and structural corrosion. There is a green concrete company that addresses this issue by greening regular concrete. http://www.youtube.com/watch?v=Pg_z3CZbr-A

  • Chuck

    I am in the process of finishing up a house made with Perform Wall, The Mexican made version of Rastra. I chose it over Durisol primarily due to local availability, but also because it’s available sizes were more conducive to my design.

    Technically, both Durisol and Rastra are ICFs and will provide many, if not all, the benefits Todd mentions. One significant difference, to me, is that they are built with recycled content, which is not the case with many (most?) ICFs.

    Both of these products are porous and need to be coated to keep water out. Wind driven rain will wick thorough it to the interior if it isn’t sealed. I used brick on the outside and plastered the interior. While I live in a very dry climate, I would not hesitate to use Perform Wall/Rastra in a wet climate if it is properly sealed.

    I found a fair amount of disparity between pieces of wall form. The two pieces that are glued together to create each wall form occasionally appear to have slid slightly before the glue set, making for forms that were not precisely square. The polyurethane foam used to assemble the walls filled gaps well, but shims were sometimes needed for precise placement. Large metal staples are required to hold the forms together while the glue cures.

    There was also a degree of difference from piece to piece in the consistency of the material itself. Some being very solid with a relatively high cement content and others being softer and almost crumbly. This is really not an issue unless one is doing a lot of modification to the forms as I was while constructing a curved wall. I actually preferred the slightly crumbly consistency as it shaped easier with hand tools.

  • Chuck

    I am in the process of finishing up a house made with Perform Wall, The Mexican made version of Rastra. I chose it over Durisol primarily due to local availability, but also because it’s available sizes were more conducive to my design.

    Technically, both Durisol and Rastra are ICFs and will provide many, if not all, the benefits Todd mentions. One significant difference, to me, is that they are built with recycled content, which is not the case with many (most?) ICFs.

    Both of these products are porous and need to be coated to keep water out. Wind driven rain will wick thorough it to the interior if it isn’t sealed. I used brick on the outside and plastered the interior. While I live in a very dry climate, I would not hesitate to use Perform Wall/Rastra in a wet climate if it is properly sealed.

    I found a fair amount of disparity between pieces of wall form. The two pieces that are glued together to create each wall form occasionally appear to have slid slightly before the glue set, making for forms that were not precisely square. The polyurethane foam used to assemble the walls filled gaps well, but shims were sometimes needed for precise placement. Large metal staples are required to hold the forms together while the glue cures.

    There was also a degree of difference from piece to piece in the consistency of the material itself. Some being very solid with a relatively high cement content and others being softer and almost crumbly. This is really not an issue unless one is doing a lot of modification to the forms as I was while constructing a curved wall. I actually preferred the slightly crumbly consistency as it shaped easier with hand tools.

  • Another interior and exterior finish alternative is KEIM’s UniversalPutz Render systems for a crack-free 100% mineral plaster finish with a silicate coating to protect the plaster for decades of service. From interior self cleaning Ecosil ME to exterior Granital, Royalan and Soldalit, KEIM has a proven 130 year history for these finishes. KEIM is unique with 77-83 perms permeability yet water resistant and will not contribute to fire or smoke. These are complete mineral systems that offer another choice beyond the traditional.

  • Another interior and exterior finish alternative is KEIM’s UniversalPutz Render systems for a crack-free 100% mineral plaster finish with a silicate coating to protect the plaster for decades of service. From interior self cleaning Ecosil ME to exterior Granital, Royalan and Soldalit, KEIM has a proven 130 year history for these finishes. KEIM is unique with 77-83 perms permeability yet water resistant and will not contribute to fire or smoke. These are complete mineral systems that offer another choice beyond the traditional.

  • Another interior and exterior finish alternative is KEIM’s UniversalPutz Render systems for a crack-free 100% mineral plaster finish with a silicate coating to protect the plaster for decades of service. From interior self cleaning Ecosil ME to exterior Granital, Royalan and Soldalit, KEIM has a proven 130 year history for these finishes. KEIM is unique with 77-83 perms permeability yet water resistant and will not contribute to fire or smoke. These are complete mineral systems that offer another choice beyond the traditional.

  • Steve Nurse

    I built my house in Northern California wine country using Rastra. I commonly get 100 degree days here an I never use my AC ( the house design has overhangs on the South facing walls so that contributes to shading also. I’ve just had an attic fire and the Rastra material saved me from losing the whole house. This stuff takes a couple of tricks to use properly, but in the great scheme of things it’s terrific. I don’t think it matters if it’s perfomr wall or Rastra, they are pretty much the same. The real trick is sealing the outside from wind driven rain – I’m having water problems, Howver, that’s because I used a conventional brown coat and elstomeric finish without first applying a seal coat before the brown coat. I’m now looking for a solution to cover the finish to make it completly water proof. This KEIM product looks intersting.

  • Steve Nurse

    I built my house in Northern California wine country using Rastra. I commonly get 100 degree days here an I never use my AC ( the house design has overhangs on the South facing walls so that contributes to shading also. I’ve just had an attic fire and the Rastra material saved me from losing the whole house. This stuff takes a couple of tricks to use properly, but in the great scheme of things it’s terrific. I don’t think it matters if it’s perfomr wall or Rastra, they are pretty much the same. The real trick is sealing the outside from wind driven rain – I’m having water problems, Howver, that’s because I used a conventional brown coat and elstomeric finish without first applying a seal coat before the brown coat. I’m now looking for a solution to cover the finish to make it completly water proof. This KEIM product looks intersting.

  • Steve Nurse

    I built my house in Northern California wine country using Rastra. I commonly get 100 degree days here an I never use my AC ( the house design has overhangs on the South facing walls so that contributes to shading also. I’ve just had an attic fire and the Rastra material saved me from losing the whole house. This stuff takes a couple of tricks to use properly, but in the great scheme of things it’s terrific. I don’t think it matters if it’s perfomr wall or Rastra, they are pretty much the same. The real trick is sealing the outside from wind driven rain – I’m having water problems, Howver, that’s because I used a conventional brown coat and elstomeric finish without first applying a seal coat before the brown coat. I’m now looking for a solution to cover the finish to make it completly water proof. This KEIM product looks intersting.

  • Sindy Singh

    You all seem to be experts in this field or at least you have had some experience with the product. What are the prices like for Rastra? Is is suitable for a tropical climate? Is there training or trained professionals available to install this product? I am guessing that regular construction guys, can’t do the job.

  • Sindy Singh

    You all seem to be experts in this field or at least you have had some experience with the product. What are the prices like for Rastra? Is is suitable for a tropical climate? Is there training or trained professionals available to install this product? I am guessing that regular construction guys, can’t do the job.

  • truly

    My husband and i are not professional builders, we’re “farmer builders”. We built our own 1200 sf winter home out of Rastra. It is easy to work with and goes up super fast. it is all the finish work that takes time, but that is the case with traditional stick built too. We did have some friends who had built with Rastra (also DIYers) who gave advice, etc. Of course there are things we’d do differently if doing it again, but overall, we love our Rastra house and believe it to be a real DIY-friendly product.

  • truly

    My husband and i are not professional builders, we’re “farmer builders”. We built our own 1200 sf winter home out of Rastra. It is easy to work with and goes up super fast. it is all the finish work that takes time, but that is the case with traditional stick built too. We did have some friends who had built with Rastra (also DIYers) who gave advice, etc. Of course there are things we’d do differently if doing it again, but overall, we love our Rastra house and believe it to be a real DIY-friendly product.

  • truly

    My husband and i are not professional builders, we’re “farmer builders”. We built our own 1200 sf winter home out of Rastra. It is easy to work with and goes up super fast. it is all the finish work that takes time, but that is the case with traditional stick built too. We did have some friends who had built with Rastra (also DIYers) who gave advice, etc. Of course there are things we’d do differently if doing it again, but overall, we love our Rastra house and believe it to be a real DIY-friendly product.

  • roxane

    I’m considering using Rastra for a walkout basement for a superinsulated cottage in Vermont. I would love to talk to someone in the northeast who has used the product and has figured out how to make it waterproof. Please contact me at roxanejj@yahoo.com. I need to make a decision soon as plans need to be completed by Feb 2010. My place will be a simple 24×32 rectangle. I would love to see your place if you are in New England! Thanks.

  • roxane

    I’m considering using Rastra for a walkout basement for a superinsulated cottage in Vermont. I would love to talk to someone in the northeast who has used the product and has figured out how to make it waterproof. Please contact me at roxanejj@yahoo.com. I need to make a decision soon as plans need to be completed by Feb 2010. My place will be a simple 24×32 rectangle. I would love to see your place if you are in New England! Thanks.

  • John Neville

    I built a home in Sedona, AZ with Rastra Block in 2003-4. I had the Rastra people put up the walls to be sure things were done right – they weren’t. The home works fine in the hot months – we have no AC – and not as great in the cold. Oriented for passive solar gain, the south walls warm up nicely during the winter. This warming also causes expansion and contraction issues with the 30-40 degree temperature drop over night and the rapid cooling that takes place. We have cracks. Also, the north walls never warm up. There is not enough insulation value in Rastra for the wall to function without the thermal mass of the concrete. In the north walls, the thermal mass never functions. Cold north walls.
    Also there are serious issues with water infiltration. Rastra is porous and allows water to pass through easily. In driving rains, water comes into the walls. Some flows down the outside of the building taking lime and other materials from the stucco across the windows – a real pain to clean. Some water flows inside the home when the water hits a window frame and is redirected. If you use Rastra, you have to make sure water cannot get into the walls – use a water barrier – which we did not. Treat the building like a stick building – waterproof anything that comes in contact with soil – keep water away from the walls, if possible – do NOT seal the walls – allow the walls to breathe to release any water vapor that collects from the inside or outside – but keep water away from the walls. If you are really considering ICF construction, you may want to look into the closed cell forms which do not allow water to pass.

  • John Neville

    I built a home in Sedona, AZ with Rastra Block in 2003-4. I had the Rastra people put up the walls to be sure things were done right – they weren’t. The home works fine in the hot months – we have no AC – and not as great in the cold. Oriented for passive solar gain, the south walls warm up nicely during the winter. This warming also causes expansion and contraction issues with the 30-40 degree temperature drop over night and the rapid cooling that takes place. We have cracks. Also, the north walls never warm up. There is not enough insulation value in Rastra for the wall to function without the thermal mass of the concrete. In the north walls, the thermal mass never functions. Cold north walls.
    Also there are serious issues with water infiltration. Rastra is porous and allows water to pass through easily. In driving rains, water comes into the walls. Some flows down the outside of the building taking lime and other materials from the stucco across the windows – a real pain to clean. Some water flows inside the home when the water hits a window frame and is redirected. If you use Rastra, you have to make sure water cannot get into the walls – use a water barrier – which we did not. Treat the building like a stick building – waterproof anything that comes in contact with soil – keep water away from the walls, if possible – do NOT seal the walls – allow the walls to breathe to release any water vapor that collects from the inside or outside – but keep water away from the walls. If you are really considering ICF construction, you may want to look into the closed cell forms which do not allow water to pass.

  • John Neville

    I built a home in Sedona, AZ with Rastra Block in 2003-4. I had the Rastra people put up the walls to be sure things were done right – they weren’t. The home works fine in the hot months – we have no AC – and not as great in the cold. Oriented for passive solar gain, the south walls warm up nicely during the winter. This warming also causes expansion and contraction issues with the 30-40 degree temperature drop over night and the rapid cooling that takes place. We have cracks. Also, the north walls never warm up. There is not enough insulation value in Rastra for the wall to function without the thermal mass of the concrete. In the north walls, the thermal mass never functions. Cold north walls.
    Also there are serious issues with water infiltration. Rastra is porous and allows water to pass through easily. In driving rains, water comes into the walls. Some flows down the outside of the building taking lime and other materials from the stucco across the windows – a real pain to clean. Some water flows inside the home when the water hits a window frame and is redirected. If you use Rastra, you have to make sure water cannot get into the walls – use a water barrier – which we did not. Treat the building like a stick building – waterproof anything that comes in contact with soil – keep water away from the walls, if possible – do NOT seal the walls – allow the walls to breathe to release any water vapor that collects from the inside or outside – but keep water away from the walls. If you are really considering ICF construction, you may want to look into the closed cell forms which do not allow water to pass.

  • Jon McLelland

    Thanks for all the comments here. I’m an architect and have two Rastra houses going right now, one nearly complete and one just coming out of the ground. It’s a system I’ve wanted to work with for a long time, and so far it seems to be all I’d hoped it would. We’ve used the 12″ blocks, and the walls are amazingly stout. There’s a very noticeable temperature and acoustic difference between inside and outside, even without windows and doors in place. Because it’s a new system where I am (in Alabama), there’s still a fair amount of nervousness among builders about how to deal with it. Our builder still isn’t really satisfied with the water-management advice we’ve gotten so far. Anybody else out there who’s used it and can recommend solutions, I’d love to hear from you.

  • Jon McLelland

    Thanks for all the comments here. I’m an architect and have two Rastra houses going right now, one nearly complete and one just coming out of the ground. It’s a system I’ve wanted to work with for a long time, and so far it seems to be all I’d hoped it would. We’ve used the 12″ blocks, and the walls are amazingly stout. There’s a very noticeable temperature and acoustic difference between inside and outside, even without windows and doors in place. Because it’s a new system where I am (in Alabama), there’s still a fair amount of nervousness among builders about how to deal with it. Our builder still isn’t really satisfied with the water-management advice we’ve gotten so far. Anybody else out there who’s used it and can recommend solutions, I’d love to hear from you.

  • Jon McLelland

    Thanks for all the comments here. I’m an architect and have two Rastra houses going right now, one nearly complete and one just coming out of the ground. It’s a system I’ve wanted to work with for a long time, and so far it seems to be all I’d hoped it would. We’ve used the 12″ blocks, and the walls are amazingly stout. There’s a very noticeable temperature and acoustic difference between inside and outside, even without windows and doors in place. Because it’s a new system where I am (in Alabama), there’s still a fair amount of nervousness among builders about how to deal with it. Our builder still isn’t really satisfied with the water-management advice we’ve gotten so far. Anybody else out there who’s used it and can recommend solutions, I’d love to hear from you.

  • louis abrams

    we’re about to purchase a rastra=made home in colorado and since it’s a major investment for us we are extremely interested in knowing, with a five-year-old home, how a buyer can determine if it was “done right” or not? this seems to be the burning issue from what we are reading, whether or not the installation of rastra block was done propertly in order to manage water issues–and how can one tell ‘afterwards’ please?

  • louis abrams

    we’re about to purchase a rastra=made home in colorado and since it’s a major investment for us we are extremely interested in knowing, with a five-year-old home, how a buyer can determine if it was “done right” or not? this seems to be the burning issue from what we are reading, whether or not the installation of rastra block was done propertly in order to manage water issues–and how can one tell ‘afterwards’ please?

  • louis abrams

    we’re about to purchase a rastra=made home in colorado and since it’s a major investment for us we are extremely interested in knowing, with a five-year-old home, how a buyer can determine if it was “done right” or not? this seems to be the burning issue from what we are reading, whether or not the installation of rastra block was done propertly in order to manage water issues–and how can one tell ‘afterwards’ please?

  • We have a 10 year old RASTRA home that was built with a traditional tree coat stucco finish. Since construction we have had problems with water at the floor level after a hard rain. The water appears to be moving behind the stucco and passing through to the inside when it hits the floor slab. Since we have colored plaster interior walls this is a real problem. Short of painting the outside of the house, has anyone found a solution to this type of problem? We hate to give up our hard troweled stucco finish fo a painted surface.

  • Gurmacher

    can rastra be used to fillĀ  in and use as a stucco material to be troweled on.
    in other word can it be used together with and blend into a house that had previously been stuccoed.
    don’t want to remove old stucco.
    reply to ; gurmacher@msn.com

  • Thomas Roth

    Rastra strikes me as being among the better products on the market along with DAC-ART blocks. As with everything the devil is in the details. Proper flashing using stainless or lead coated copper along with proper finish coatings in the case of Rastra make all the difference. Waterproofing below grade with high quality materials such as Laurenco will ensure everything stays dry. One should note that none of these products come cheap. Any ICF or precast concrete unit structure will always be more expensive to build than a wood framed home, and any offset you would achieve from energy savings would be negligible when considered against a properly framed and insulated 2×6 stud wall. However, there are advantages to Rastra and a product like DAC-ART when you consider damage due to hurricanes or flooding. Neither a Rastra or DAC-ART building will suffer much if any damage due to flooding whereas a wood framed wall will need to be gutted and cleaned of mold. A Rastra or DAC-ART building would also be inherently stronger and able to take a lot more punishment from high velocity impacts not to mention its low maintenance exterior finish.

  • We are going to be building a treehouse and want organic lines and a lot of curves and that would be hard to achieve doing stick built . It occured to me that using rastra block filled with some kind of foam rather than concrete so it is lightweight could do the trick. Anyone know if number one this is feasible, two if it could withstand the load or need to be post and beam and three if there is a green foam product out there that could be used instead of concrete for infill. Any comments would be appreciated.