I need help with weep holes in a retaining wall and the use of speed blocks.


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Old 07-20-07, 02:26 PM
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Question I need help with weep holes in a retaining wall and the use of speed blocks.

Do you lay speed blocks from one end of the wall to the other, or start at the corners and then fill in the middle? I've found some info online that shows building up each corner first, then filling in the middle of each row. This example I saw showed building four walls to form a square and also used only the rectangular concrete blocks.

My project differs from the example I saw however. I am building one straight wall about 7 ft long and 7 ft tall. I am only using rectangular concrete blocks on the ends and am using speed blocks (the H shaped "mortarless head joint" blocks) in the middle to fit around the rebar. Here's the website with the instructions and illustrations I came across while looking for info about using a mason's line that has caused my new dilemna.

http://www.bhg.com/bhg/story.jsp?page=2&catref=cat240036&storyid=/templatedata/bhg/step-by-step/data/hie_307.xml

The wall has been properly engineered and has a huge footing with a good sized key in it so don't worry about that aspect of my project. I actually already laid the first row perfectly level and plumb, but didn't use a mason's line. In the middle one of the speed blocks was warped/crooked and I thought I had it straight and flush, but my eye must not be as good as I thought it was. The wall veered slightly to the left after that brick. It bothered me so much when I looked down it not to see a straight line that I pulled the bricks off and am going to start over. Hence my mason's line research. I shouldn't have ignored the mason's line part of the instructions my father-in-law gave me, especially when a mason's line is referred to on the mortar mix bag too. I guess you live and you learn though.

I've learned that the speed blocks technical name is "mortarless head joint." I'm assuming that mortar on the vertical sides of the block isn't needed because of the way they connect together and because of the name, but it would be great if anyone could verify that for me that I don't need to apply mortar to the vertical sides.

Last but not least, on to the weep holes. I'm putting in 4 inch drain pipe in the felt sock and also laying felt below the pipe and above the drain rock. Do I need to make weep holes as well? How many will I need and how should I make and space them? Thanks!
 
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Old 07-20-07, 03:43 PM
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I need help with weep holes in a retaining wall and the use of speed blocks.

When you say "speed block", that a a term that has been used for many different common block around the world. What do the block look like?

What are your trying to build? - Basement, home, retaining wall, motel ot high rise apartment building?

If it is properly engineered, you should have some details and construction specifications to go by. If not, be prepared for and inspection.

Few mortarless block walls are approved for use in buildings in the U.S.

Are you in California and trying to build a 7' high wall?

Dick
 
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Old 07-20-07, 08:49 PM
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I am not familiar with "speed block", but regardless, you build "leads" at both ends of the run and then fill between them. You use a level to check level and a plumb on the leads then use a line to maintain coursing and trueness of the run.
 
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Old 07-21-07, 07:16 AM
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Speed Blocks

The speed blocks are H shaped gray concrete blocks. They slightly interlock with a little tongue and groove type of design at the end. They are also rectangularly shaped, but the ends are open, hence the H shape.

I'm using the corner rectangular blocks on the end and half blocks.

There is mortar along the horizontal surface of the bricks and vertically on the corner bricks. I don't think I need to put it vertically on the surface of the speed blocks, but was hoping someone could verify that.

My question of if I should lay out the corners first is because if they are laid that way then when it comes time lay the closure brick in the middle it seems possible that the last block may not fit in the interlocking design regardless of how careful I am. It would be simple to just cut it to fit if that happened, but I just want to find out if people lay them from one end to the other because of the interlocking design or if they generally start at the corners as is the link below.

I learned that these H shaped cement blocks are called speed blocks or mortarless head joints from wikipedia. The speed block info is in the last paragraph fyi. Here's the info:

A Concrete masonry unit (CMU) [US], concrete block, or breeze block [UK], cinder block or foundation block [US], clinker block (if bottom ash or clinker is used as an aggregate) is a large rectangular brick used in construction. Concrete blocks are made from cast concrete, i.e. portland cement and aggregate, usually sand and fine gravel in the case of blocks. They are formed typically in the shape of two squares joined on one side to form a rectangle, with the insides of the squares hollow. This allows structures to be built in the traditional masonry style of overlapping rows, with the structure's weight carried by the "walls" of the blocks.

Concrete block, when reinforced with concrete columns and tie beams, is a very common building material for the load-bearing walls of buildings, in what is termed CBS construction for Concrete Block Structure. Suburban houses typically employ a concrete foundation and slab with a concrete block wall on the perimeter. Large buildings typically use copious amounts of concrete block; for even larger buildings, concrete block supplements steel I-beams. Tilt-wall construction, however is replacing CBS for some large structures. The holes inside concrete block allow rebar and concrete (creating reinforced concrete) to run vertically through the block to compensate for the lack of tensile strength. Because most people find the appearance of concrete block to be drab and unattractive, exposed surfaces are generally given a decorative finish of stucco, brick, paint or siding.

When the rebar running vertically through a concrete block wall is anchored, as is usually the case, into the foundation or floor slab before the wall is built, it presents a potential problem in assembling the wall, since every block might need to be lowered from the rebar tops to its resting place in the wall. This problem is solved by using a style of open-ended block whose plan form resembles the letter "H", commonly known as a mortarless head joint or speed block. Speed blocks can be maneuvered between the reinforcing bars and tilted into place; the vertical spaces are then filled with concrete as with ordinary Concrete blocks.
 
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Old 07-21-07, 08:02 AM
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Smile I got an answer! What do you think?

I posted my question also on allexperts.com and got an answer from Dave Coil. It answers it all, except it doesn't address if they should be laid from one end to the other or not. I'm pretty happy with it overall though. Here's what he had to say.

Speed blocks are fun to lay up...fast. They are T&G so mortar is not wanted, or needed. You would only need weep holes if your grade is such that the water cannot easily flow from end to end. If the grade is too low...the weep hole would be a stop gap measure to exit the water with minimal carry. That string mason line is so easy to forget...and so important when used.
 
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Old 07-21-07, 08:10 AM
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If you are building a CMU reating wall, and you have provided for drain to daylight, you do not weep the wall through the face.

As for your other question, the units are modular, that is to say all the same size, nominally, so you lay out the wall and the leads so that your closer is not a cut. If in your layout you can not avoid a cut closer, then make the cut on the leads. Once the leads are built, you do not normally lay from both ends to the center, unless 2 persons are working the line.
 
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Old 07-21-07, 09:06 AM
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Smile Many thanks everyone!

I appreciate all the help! I guess I'd better get to work now that I've got it all figured out.
 
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Old 07-21-07, 02:00 PM
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I need help with weep holes in a retaining wall and the use of speed blocks.

If you are not filling the wall solid with grout, you are totally incorrect when you assume the mortar on the head joint is not needed because the block is designed that way.

In 40 years in the concrete masonry, for ungrouted construction, I never been able to find a block wall without head joints and grout that was even close to a wall with head joints. This include the U.S and 37 different countries.

Without head joints you do not comply with any of the U.S. codes

Vertical load capacity will be reduced by at least 20% if you have a bond beam on top and over 50% without a bond beam.

Longitudinal shear strenght wil be reduced at least 30-40%.

Transverse shear will be reduced at least 25%.

If you are using the type of blocks with a minmum face shell and web thicknesses, the reductions would be even more.

I hope whoever engineered the wall knew what type of units you are using, because a 7' high wall is very dangerous.
 
 

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