Concrete Block size confusion

[Sparticle]

We're building a dry stack block house. We have many books we're using to design the house, but used Rob Roy's concrete block chart for the sizes of the blocks. I've just finished laying out the two houses (two small houses together for mother-in-law and us) so that the wall sizes and placement of windows and doors are based on the actual length of the blocks. Everything is in 8th's of an inch, so this took a little time.

I was reading my Surface bonded brochure from the FDA and they have a concrete chart as well. I didn't notice till last night though that their numbers were different.

Rob Roy said 7 3/8 x 15 3/8. USDA said 15 5/8 x 7 5/8. I went out and measured the blocks and they were actually 7 11/16, so we'll call them 7 5/8th.

Can you think of a reason he'd list the sizes differently? Is there something I"m not thinking of or do you think this is simply a typo?

After 2 years of working on these designs and a million re=-works, I was ready to get the roof span and floor plans to the architect today. Now I have to go fix all my dang numbers. Good thing is, I didn't draw to the 8th of an inch. Everything I drew was to the whole inch so at least I don't have any lines to change. I sure hope these drawings are over soon.

[kvr28]

we bought robs first book over 15 years ago, we planned the whole time and finally built it last year, if your going to fill the cores don't sweat it, you can cut the blocks with a diamond tipped circular saw to fit them, make sure you get some coil stock to shim and level the blocks, that was the hardest part of the whole process, we didn't go totally underground, we just went earth sheltered.

[cfabe]

Since blocks are designed to be laid in mortar where the mortar can be used to take up any variance in size, they are not always as dimensionally consistent as you might assume. While building your house, keep that in mind. If you get blocks from two different suppliers, or even two lots from the same supplier, the dimensions may vary and you'll have to adjust for that while building.

[Sparticle]

I know the block sizes are that way for the mortar, however we are using the dry stack method so that changes everything. We have the raw dimensions of the blocks to deal with. There is a course of mortar under the first course for leveling, then they are stacked dry and surface bonded.

http://naldr.nal.usda.gov/exe/zynet....kPage=f&Rank=1

[oneokie]

Originally Posted by Sparticle

Rob Roy said 7 3/8 x 15 3/8. USDA said 15 5/8 x 7 5/8. I went out and measured the blocks and they were actually 7 11/16, so we'll call them 7 5/8th.

Can you think of a reason he'd list the sizes differently? Is there something I"m not thinking of or do you think this is simply a typo?

The difference is because they are planning/using different thickness mortar between the blocks. Rob Roy uses 5/8" thick joint, USDA uses 3/8" joint.

[ErinP]

Rob Roy doesn't use a joint. He dry stacks as the OP is wanting to do.


I, too, have noticed he's off by a fraction of an inch. However, we were foolish enough to not double check before we put our footers in!
Fortunately, our footers are overbuilt, so we can be off-center a smidge to make up for the difference and, ours are for our basement only, and it'll actually fit under the house foot-print better.

We got lucky! lol
But yeah, I've noticed the discrepancy, too.

[Sparticle]

I'm just glad I caught it before the footers went in!

[highlands]

I solved the problem with a diamond.
We cut block, and stone, as needed.
Part of our tiny cottage is dry stacked.
Don't worry about the tiny gapping. The parge can fix it.
We then parged the faces and core poured with rebar.
I like buildings that stay up.

http://flashweb.com/blog/2007/10/600...y-cottage.html

Cheers

-Walter
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
Read about our on-farm butcher shop project:
http://SugarMtnFarm.com/butchershop
http://SugarMtnFarm.com/csa

[Sparticle]

Originally Posted by highlands

I solved the problem with a diamond.
We cut block, and stone, as needed.
Part of our tiny cottage is dry stacked.
Don't worry about the tiny gapping. The parge can fix it.
We then parged the faces and core poured with rebar.
I like buildings that stay up.

http://flashweb.com/blog/2007/10/600...y-cottage.html

Cheers

-Walter
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
Read about our on-farm butcher shop project:
http://SugarMtnFarm.com/butchershop
http://SugarMtnFarm.com/csa

Thanks! It's still weird in the differences in block sizes. Over the course of the whole building it made quite a difference and our footers would have been short. So everyone should measure a block first and not rely on print!

[highlands]

When we did our cottage, which is a very small building, we did a floating pad. All the concrete block sits on the pad so everything is stable and locked together. Rebar projects from the pad up into the block courses. I mortared the first course to the pad and had left that area particularly rough to gain extra adhesion. Before mortaring I washed it with slip (cement & water).

[jlrbhjmnc]

Sparticle - would you mind sharing the list of books you used in planning for your home?

[Sparticle]

Originally Posted by jlrbhjmnc

Sparticle - would you mind sharing the list of books you used in planning for your home?

I can share the books we have. Many were borrowed too and long since given back, some were checked out in the library. Some were too good not to find used and buy for ourselves and I'll give you the list of those.

I'll work on that tomorrow - tired.

[jlrbhjmnc]

Thanks! Looking forward to it.

[wheeezil]

www.texasmusicforge.com/gimmeshelter.html

[Sparticle]

Originally Posted by wheeezil

www.texasmusicforge.com/gimmeshelter.html

We've seen that one before thanks!

[Sparticle]

Originally Posted by jlrbhjmnc

Sparticle - would you mind sharing the list of books you used in planning for your home?

Someone donated a box of Fine Homebuilding magazines and they are awesome! I'm pretty sure we got all these books on half.com or somewhere like that cheap and used. The library also had a lot of books we checked out but weren't worth buying.

For dry stack surface bonded method, use the USDA brochure (now out of print) but found online here:

http://naldr.nal.usda.gov/exe/zynet....kPage=f&Rank=1


Best books:
"Earth-Sheltered Houses" - Rob Roy (though the block chart is wrong in there, don't use it)
"The Best of find Homebuilding Foundations & Concrete work" - by Fine Homebuilding magazine. Great articles in there!
"Underground Root Cellar" Phyllis Hobson "A storey country wisdom bulletin"
"Earthen Floors" by Athena and Bill Steen
"Build your own Earth Oven" - Kiko Denzer
"Serious Straw Bale" - Paul Lacinski and Michel Bergeron
"Building with Earth" - Chelsea Green
"Living Homes" - Thomas Elpel

Other books used:
Real Goods "Solar Living Source Book"
"The Stone Builders Primer" Charles Long
"The Straw Bale House" - Athena & Bill Steen
"Building Underground" - Herb Wade
"Homing Instinct" - John Connell
"The Underground House Book" - Stu Campbell
"The Natural House" - Daniel Chiras
"The Natural House Book" - David Pearson
"Using Natural Finishes" - Adam Weismann & Katy Bryce
"Build your own Stone House" - Karl & Sue Schwenke
"earth sheltered Homes" - Van Nostrand
"The solar House" - Chiras
"Design for Water" - Heather Kinkade-Levario
"Natural Home Heating" - Greg Pahl
"Building with Stone" - Charles McRaven

[jlrbhjmnc]

Sparticle - THANK YOU for your generous response to my question. Wow! We really appreciate your time and effort with this list of resources.

wheeezil - We checked out the "gimme shelter" blog thing - inspiring.