Construction FAQ Page. Our Block
Forum may also provide additional information.
Errata Page for Book Changes
our Certification Standards page
update: 24 Jan 2014, newest additions are at the top of this list.
Tie-down strap installation? Refer
to the New errata page link above for this discussion.
how many blocks are needed to complete a wall?
Wall length x 0.75 x rows high will provide the block count for that
wall. This is a good rule of thumb. Of course windows and doors will
reduce this count a little, but that allows for broken blocks and
Wall 51-feet long and 14-blocks high = 51x14x0.75=535.5 -blocks.
you use conventional siding in lieu of SBC?
Defiantly not! The SBC is an integral part of the walls structural
strength. You could place conventional siding on top of the SBC, if
you don't like the stucco appearance. This would be difficult and
costly. The cost of the SBC is considerably less than the cost of
external siding, not to mention the SBC durability and color fast
properties. Home construction with SBC has several advantages.
website references disagree with your block dimensioning numbers.
Why is this?
These other references most likely contain some very useful information,
but conflicting dimension numbers will not be useful to you at all.
I suspect these numbers came from an engineer who never actually completed
a structure. Other references could just be carelessness or referencing
of bad sources for their numbers.
"other" dimension numbers are good in a virtual world, but
they don't cut it in the real world. I just went outside and re-measured
my actual house walls (the first 6 rows before I learned about wall
growth) and the bottom row of 8 blocks is exactly 10' - 5-1/2"
long. This matches my old tables (13 Jun 05 which is NOT in the book)
that have been modified in the published book (and this website).
Do the math for an alternate numbers system (such as mha-net.org/msb/docs/surfbond.PDF)
and you get 125" = 10' - 5" + 1/4" = 10' - 5-1/4".
Notice that my bottom row measures 10' - 5-1/2" which already
violates their numbers. My fifth row measures
10' - 5-3/4" due to wall growth. This violates my original chart
(13 Jun 05 which is NOT in the book). My new charts in the book and
on this website call for 10' - 6" for those same eight blocks.
Bottom line, their numbers just don't work in the real world. My house
blocks were stacked as tight against each other as I could get them.
numbers in the book and on this website provide for a little excess.
Remember, you can't squeeze that closing block if it is 1/16"
too long. But you can space out adjacent closing blocks slightly to
incorporate any slight gap. You can also mortar any closing block
gap that is less than 3/4". The SBC will fill any small gaps
and reinforce any mortared gaps. This will prevent wall weakness at
the gap locations. You also have a full block above and below any
gap due to the running bond pattern. This results in very solid home
can't I just drill holes in the foundation and insert the cell rebar?
You can; but it won't pass code. The wall openings page
on this website demonstrates what is required by most building codes.
Don't forget that high winds create tremendous uplift forces on the
roof structure. This is why the code requirements are as specified.
about lining forms with plastic?
I personally would never go there!. Any wrinkle or air pocket under
the plastic will result in a void on the concrete surface. I know
from experience in my early header pours that any wrinkle or bulge
in the vapor barrier will result in a void of the poured concrete.
Common sense tells you that the weight of the concrete would flatten
out any wrinkles, but in reality the wrinkles result in a void. If
air bubbles remain and leave voids, (that is why they vibrate the
wet mix for federal jobs) isn't it also reasonable to believe that
plastic wrinkles could also leave a void?
about shimming dry stacked blocks?
Ah yes, those metal shims. Some people also say you can use sand for
shimming. That makes sense because sand granules can't be compressed.
I never found a need for shims. I found that once in a while an imperfect
block will rock slightly, but when you place the next row on top,
the weight above stops the rocking. The SBC will fill that slight
gap, and the sun will rise the next day. If there is a lot or rocking,
either replace that block or fix the underlying (literally underlying)
problem. Do the shimmy shimmy if you desire; I just never found a
need for it. Of course, I also remortar the seventh row to reduce
wall growth and to greatly improve stacked wall stability above row
seven during construction.
you know of a source for plastic shims?
I have never looked into plastic shims, but nylon would probably be
stronger. I will do some research on this shim source question. My
first inclination would be to use nylon cable ties with the clicking
end cut off. Of course, the non-metal shim should not be load bearing
in my opinion. This could make the wall unstable before the SBC is
applied. Some of my walls (with poured wall cells and bond-beam) have
remained standing for a year awaiting the SBC application and I would
not want any nylon or plastic involved in the wall stability before
application of the SBC.
My general experience is that a rocking block doesn't really matter
unless it makes other blocks unstable. If other blocks become unstable,
then you should fix the underlying source of the problem. The SBC
will close all gaps, and bonds this rocking block just like it bonds
the other blocks.
I have found that when you presort the block height (my blocks were
low cost 80 cents each, and they had three different heights, 7-1/2,
7-3/8, 7-1/4; these heights varied by pallet groupings (the entire
pallet would be same height)) then the block rocking is not a problem.
For some reason, each of my pallets also had two - five bad dimension
blocks on top.
The block can also rock diagonally and this is from out-of-plane blocks
being reversed in the row beneath. In other words, when the next row
sits on top of two blocks which have the same out of plane, but the
one block has the high side on the wall outside, and the other block
has the high side on the inside of the wall; then the block on top
My experience has been that when you sort block height and monitor
block plane by keeping the across wall level as you stack, then block
rocking is history. Only use the same height blocks in any given block
row. When the blocks are stacked tight against each other longitudionally,
then this also reduces block rocking from underlying block differences.
I recently made a video on stacking the attached garage walls using
all the concepts explained in the book, and I had just one block out
of about 250 that rocked. And that was because I missed one block
below which was the wrong height. This low cost video on DVD should
be available late May 2007. This one hour video takes you through
all the concerns of stacking a wall from footer forms up through placing
the bond-beam rebar. This DVD compliments the book.
I need end-blocks for wall openings and corners?
That is a loaded question. I am hearing from others that across the
nation all differing styles of concrete blocks can be found. I chose
to build with two-cell flat end blocks and the book explains the reasons
why. Many three-cell blocks have an open web on each end. These blocks
can not be used on corners and for wall openings. This style of block
also inventories end-blocks which have flat ends for such applications.
I don't need to order additional inventory because I use the flat
end blocks all around for my home construction.
I just make wall openings the desired width to fit the door or window?
This is not recommended. Remember that top row of lintel blocks that
are required for your bond-beam? If you fudge on the door opening,
then the block rows above the door opening will not fit because the
wall segment including that door has to remain the same at the top
and bottom. If the door opening does not follow the dimensioning tables
then the block rows above the opening will have different lengths
than the block rows below the opening. This means the top of your
wall would be different than the bottom of the same wall unless you
cut some blocks above the opening.
to come, I am sure...........