Rastra is a type of ICF (although somewhat lower on the “I” than the usual kind) that is made with cement and syrofoam (or maybe other recycled foam). I was interested in using it because of its fire protection value. However, I read that it was about $4.00/sq ft just for the Rastra, so you would need to also figure in rebar and concrete fill for a wall. If I remember correctly, these units are fairly hefty compared to standard ICFs. I also remember a couple of complaints that the Rastra that was received by some builders had been damaged in shipping, so it appears that it might be a fragile. The cost has me looking at other fire resistant building alternatives.
There is an article in today’s LA times on an architect who built his own house from Rastra. Some of you might find the article interesting:
http://www.latimes.com/features/home/la-hm-fireproofhouse13nov13,1,3032305.story
I believe there are a couple of competitors to Rastra. I read that the original US firm that licensed Rastra had a falling out with the parent company in Germany and started making their own line of similar blocks. I don’t recall the name so would appreciate anyone letting me know what it is. There is also another firm that makes a block that incorporates wood waste with cement, I believe. Any info and pricing on similar products would be appreciated.
Replies
wasn't there some guy here not to long ago complaining about why he can't find anyone to build a house out of that product?
Rastra is a unique beast to work with unlike any other ICF I,ve seen. The last house I built was part rastra. I would never ever choose to use this product ever ever again nor would I recomend it. I see no advantage in rastra. Look at Arrx block or Amvic but stay awaay from rastra unless you've money to burn and want a fight on your hands.
Jonathan
Jonathan,
DETAILS PLEASE! I too have been curious about Rastra and other forms of alternative building. Always wondered how hard or easy such a system would be to work with.
Seems from your comments that you've actually worked with the stuff. Soooo, for those of us who have not, please, please, please,.....spill your guts and give us the straight "skinny."
Thanks.
Davo
Glad to lend my perspective,
First let me say I had nothing against Rastra before working with it. I was open and still am open to new products and so on. That being said........
Rasta Is very expensive. It is very heavy. The best wasy to set the blocks is with a crane or boom (more money) The blocks are extremely brittle and if they get wet before setting them, it gets heavier and more brittle. The product itself is not 'clean' or uniform so you need to constantly shim and wedge in every direction as you go then foam each block. It lacks a good bracing system for your pour, you'll spend days gluing and nailing braces everywhere to prevent blowouts. Corners and openings for doors, windows are weak so watch them. One thing to consider is with Rastra you get concrete cells that run horizontally and vert, any other ICF gives you a solid wall. Much better in my humble opinion. In discussions I've had with my inspector I've heard talk that system like Rastra may be prohibited mainly because of the weakness that the cell wall could have. Imagine what will happen if you rest a beam on thewall where there is no concrete core. So you must be diligent and create beam pockets in the wall before you pour so there is adequate strength in the wall. If you've seen the product you'll see what I mean. OK now thinkabout hanging your cabinets. how to fasten them? then your subs. It is not fun to route cables and wires into that . Its dusty and dirty. Just because they say you can stucco and plaster (you can) doesn't mean you'll find subs willing to. Ours put up drywall (with lots of glue)on the rastra over the weekend after having been told to plaster over the rastra. I made him tear it out, not fun. they also say you can tile onto it. I would not recomend it, atleast not on any exterior wall. I've seen a Rastra house with the shower enclosure built on an ext wall that is having moisture problems. Apparently the material is so porous outside moisture is working inside and peeling paint in the bedrooms and dropping tiles in the bath. It is built with cells 15 inches on center so if you don't follow that you'll end up with lots of waste (more money). I built a basement recently with Arxx (i looked at Amvic and it seems good too) It took me a fraction of the time to set, cost a fraction of the money ,looks better, and is a stronger wall. Theres more but I'm tired of typing and you should get the drift. I hope this helps. Anymore questions let me know. FYI i'll be gone for a week from tomrrow and as such won't respond until I return.
Jonathan
I have to area with Jonathan, Rastra SUCKS big time!!! Right now I'm involved on a project which is using Rastra blocks. The manufacture rep. who I've never met (phone only) seems to know nothing about this product (he told us to glue the ledgers on for the floor system). I'm not all that educated on this product but as far as the Moisture wicking though does anyone have a solution. The only two things that I've seen good about this product so far is that it has a great fire rating and also great on keeping a quiet home. Those who have used it, did you get sold the Pro-13 glue gun? We did and learned after the 6 or 7th gun not working that we got the new and improved recalled Pro-13 (stick with the older version). Right now we are starting our third story of Rasta on a 16x26 addition and looking forward to finishing (at least lifting the blocks) and then moving inside dealing with more problems ahead. So anyway, those who like the idea of Rastra, I would check into other ICF products.
Thanks for the input, I kind of had a feeling that Rastra might be a pain given the weight of the blocks and the hints that it is rather fragile. The problem with the polystyrene blocks, as most of the ICFs are, is that the first full blown brush fire to come through my area would melt or burn off all the exterior polystyrene. My area is also a major carpenter ant area, so I would at least have to get some treated blocks, and most vendors don't list theirs as treated, although it might be available and they just don't bother to put in on their websites.
The tradition ICFs seem to come in two major catagories - the grid system where the styrofoam blocks have horizontal and verticle channels to fill with concrete but with much of the wall being nothing but polystyrene. I definitely would not want something like that facing a brushfire. The type that allows for a solid concrete wall in the center for the blocks would be better for my situation, but I am still not convinced that it would be a good idea in ant and fire country. I do agree that if you are going to use it, get the plastic ties with their lower thermal conductivity.
It looks like good old fashioned concrete walls using plywood forms is probably the best idea, although I don't look forward to setting up all the forms. I have enough forms for about 1/3 of what I need, so, given the current price of plywood, I guess I had better start looking for places to rent forms...
CaseyR,
"fire resistant building materials".........
Well, how about plain ole concrete! Check out the website http://www.Superiorwalls.com
Another "fire resistant alternative"....and I know you are gonna laugh...but, its true...try building a straw house. Once the straw is stuccoed over, it pretty much is fire proof. And, supposedly the straw bales are packed so tight that a fire cannot sustain ignition...it can only smolder a bit... least this is what I've read and heard.
Anyway, for me...concrete walls, metal roof...ESPECIALLY if I was living in California's wild fire range.
Davo
casey, Look into Hebel Block. A mason friend of mine in NC built a house using this German (I think) building idea. Here's a pic of construction and some google links.
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http://castlebuilders.com/faq.htm
Remodeling Contractor just outside the Glass City.
Quittin' Time
Edited 11/14/2003 6:30:01 AM ET by calvin
The big problem with Rastra, and the other concrete and EPS mixtures, is the static R-value is really low. The R-values they indicate are "equivalent", which means they perform like stick built in certain circumstances. Those circumstances are where thermal mass levels our daily temperature swings, like in the desert. Put that same wall in a climate that is cold for weeks at a time and it's R-value more "equivalent" to a concrete wall than a stick built.
Lots of info on a similiar but better product called Durisol. Try http://www.durisolbuild.com. It is made in Mitchell Ontario.
Edited 11/14/2003 4:22:53 PM ET by newby1