Friday, July 17, 2009

Re: [papercreters] Re: Size of blocks?



Slurryguy is absolutely right the manufacture of blocks is very time consuming.  I make blocks that are 12" long, 8" wide, and 6" thick.  I drain the mix into a draining bin for about an hour to collect almost half my water back.  Then I pour into my block forms on top of screened tables and capture more water. After about 20 minutes I can remove the forms.  I built a blender from an old 55 gallon barrel outfitted with a 4 horse motor with a weed-eater blade modified.  From the the barrel I get about 5 1/2 blocks on average.  I can roll the blocks in about a day, and move them to setting tables in about 3 days.  I have made longer blocks up to 4' long, but they take incredibly longer to dry enough to move them.  I am needing about 2600 blocks.  I do not make blocks everyday, but when I do it's about 20-25 blocks.  At the moment it feels like it is going to take forever to make enough blocks to start.
 
Jerry

--- On Fri, 7/17/09, slurryguy <slurryguy@yahoo.com> wrote:

From: slurryguy <slurryguy@yahoo.com>
Subject: [papercreters] Re: Size of blocks?
To: papercreters@yahoogroups.com
Date: Friday, July 17, 2009, 8:47 PM

In my humble opinion, the reason you are struggling to figure out block size is because you are asking the wrong question at the wrong time in your design process.

I suggest that "ideal" construction material dimensions are determined by the detailed dimensions of the structure you intend to build, the construction method that is best for you to employ, and how you expect your structure to perform.  Figuring out the answers to these questions will naturally lead to answers to such questions as block sizes.

I encourage you to consider if building with blocks is the best construction method for your situation in the first place.  Don't get me wrong, blocks are fine.  However, they may be the most labor intensive technique for building with papercrete.  You also can consider slipforming, large monolithic poured walls, and some other techniques.

If you have a tractor available that has a front-end loader, you have a very powerful tool that can be exploited to assist in pouring very large and tall vertical formwork.  You can save yourself weeks and weeks, if not months and years, of block making and layup by pouring and compressing tall wall sections at a time.  Don't hesitate to take advantage of the heavy lifting tools that are available to you.  Exploit whatever heavy equipment you can to save yourself labor and effort.  Why form, turn, stack, layup, and mortar blocks by hand if you can have a tractor pour the equivalent of hundreds if not thousands of blocks in place in a wall in one day?

Do you have a large enough work area to pour papercrete blocks on the ground and then dry them?  If you don't have a good place to make your blocks, this can be a very important consideration when thinking about other techniques like slipforming etc.




Here are a few more questions to ask yourself.  The answers to these questions will lead to the kinds of answers you are seeking:

What are the overall dimensions of your desired structure?

Will the walls be supporting a load?  Will the walls be infill only?

If he walls will be supporting a load, what load?  Typically it might be a roof structure, potential snow loads, attic insulation, ceilings, etc.  There are many standard consruction books that can help determine these load expectations for the size of structure you want.  It's not rocket science.  Find a good book for estimating construction jobs and figure out the loads you'll need to account for.  The book obviously won't mention papercrete, but don't worry about that.  Concentrate on estimating the weight of the roof you will need for your building and work your way down to include everything the walls need to hold up.

Will the walls be supporting the load evenly, or will certain walls be carrying more weight than other walls?  Some building designs have interior load bearing walls, or have a roof style that puts more weight on one wall than another wall.

All these questions about load bearing walls should eventually boil down to a number of #### pounds per linear foot for each particular wall.  Then you simply need to determine what papercrete mix and wall thickness will phyically support those loads.

It's actually a lot easier than this sounds.

For the sake of your block size question... the wall thickness is the key number.  Assuming you choose to build a wall from blocks instead of slipforming or other technique.  The most common method is to have at least one dimension of the blocks be the full thickness of the wall.  While this isn't absolutely required, it is the most common method.  Don't forget to account for shrinkage when designing your block forms.  Typically it's best to keep the vertical height of a block reasonably thin so that it will dry more quickly.  4" to 6" is probably most common.  Less than 4" can be tricky to keep from breaking while turning it while it's still damp and hasn't reached full strength yet.  Thicker than 6" height blocks take longer to dry.  However, maybe drying time isn't a critical factor for you?  If that's the case, maybe it makes sense to go with a taller block?

The lateral width of the block is usually rather arbitrary.  You want the block to be wide enough so that you can lay a nice bond block pattern in your wall and have each layer overlap the previous layer's joints nicely.  You also want the final weight of the block to be light enough you can work with it easily by hand.  Plan the lateral width of the block accordingly.





What if the walls will not be structural?  What if they are only infill walls? 

In this case, the biggest factor to determine wall thickness is what level of insuation you desire from the wall.  R-Factor for papercrete depends upon the specific recipe mix you use, but R2 to R3 per inch is very typical.  R4 per inch or so is possible, but it will require a more specialized mix, and probably high compression to get insulation values that high.

The next thing to consider is what is your climate like?  Here is an outstanding FREE software tool that can be extremely helpful in determining how much insulation makes sense for various structures:
http://mackintosh.aud.ucla.edu/heed/

Using HEED, you should be able to completely analyze the BTU's required for various particular structures in your particular climate.  When you factor in the price of various energy costs, you can calculate how much money you'll be spending to heat/cool the structure.  If you also calculate the construction cost of adding more insulation to your structure, you can easily determine how much insulation is economically optimal.  I HIGHLY recommend this tool.  It's very powerful.  While many people just pick a wall thickness out of thin air, this tool allows you to make these decisions for solid reasons that you can document.

Again... once you have determined the thickness of your infill wall... the same process applies to determining the other block size dimensions as with a structural block wall.  Drying time and safe handling determins vertical height.  Joint overlap, and weight handling considerations determine lateral block width.


Yes, I know... I've given a very verbose answer to what appears to be a very simple question.  What can I say?  It's what I'm good at!!  My brain does what it does.  I tend to think about these issues and try to understand what answer is the BEST answer and why.

At the very least, I hope I've given you, as well as others in the group some food for thought. 



Of course...  there is a completely different way to decide on block size.

You can easily just pull a number out of thin air and run with it.  Maybe you don't care if the wall thickness is the perfect size to keep your construction costs and long term energy costs to the absolute minimum?  If that's the case ... go with whatever size you want.   

Build with what works well for you and don't look back.  It's a method that has worked since the ancient Egyptians first started laying up mud bricks, and still works today.

As long as you are happy with it, who cares what all the numerical mumbo jumbo optimal design calculations say.  It's your house.  Build it your way.





--- In papercreters@yahoogroups.com, Evelyn Vollmer <evelynanne8@...> wrote:
>
> Could some of you tell me about size of blocks, what size would be best? I
> have an idea of what eventually I want to build but have not thought on the
> size, thickness, etc (and why) of a wall for a small dwelling. I don't think
> I would tackle a dome type structure at this time. I am sure this question
> sounds simplistic but any info would help me decide. Thanks in advance, Ev
>
> --
> Chinese herbals for the Western Mind
> www.ozbotanicals.com
> Skype~eve8mon
>




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