Home Construction FAQ Page. Our Block Forum may also provide additional information.

New Errata Page for Book Changes

See our Certification Standards page

Last update: 24 Jan 2014, newest additions are at the top of this list.

Truss Tie-down strap installation? Refer to the New errata page link above for this discussion.

Approximately. 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 small errors.

Example: Wall 51-feet long and 14-blocks high = 51x14x0.75=535.5 -blocks.

Can 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.

Other 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.

These "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.

My 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 construction.

Why 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.

What 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?

What 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.

Do 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 rocks diagonally.

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.

Don't 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.

Can't 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.

More to come, I am sure...........

Return to Top

Copyright © 2006-2022 Nefcon, contact us at support@gonefcon.com
Reproduction or republication strictly prohibited without prior written permission.
See Website Rules for further legal information.
Website owned & operated by Nefcon
Update:01Jan2022, webmaster@gonefcon.com