May 14, 2010

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How to Build A Block Foundation

In today’s post we are going to discuss how to build a concrete block foundation and the tools you will need to complete this task.  You should have a good construction knowledge and be in good physical shape before attempting to do this.  One thing you should do though is have the hole dug and the footers in place by a licensed excavator to ensure you at least have a good starting point.

Lets go over what you will need for this job first, you will need a cement mixer, partner saw, wheelbarrow, mortar boards,a laser for elevations, scaffolding and plank if you are building a basement.  The hand tools you will need are a trowel, hammer, striker, chalk box, line, line bars and a 2ft and 4ft. level.

So lets get started, with your footers in place the first you need to do is layout your job and mark all of your corners with a concrete nail or a pencil.  This can be a time consuming process so be sure you have someone to help you measure everything out to be square.  After you have you corners marked take your chalk box and pull it from corner to corner and snap a line mark down onto your footer, this is the line that your block will follow.

Next you will need to establish your elevations with your laser, i recommend you get a self leveling laser because the slightest error in this step can be very bad in getting your foundation level.  Establish which corner is the highest and use it to set all of your other heights.  Be sure to mark each corner with how much you need to raise it so you don’t get confused.

Now it is time to build your leads, with all your corners marked lay in your first course, if you need to raise a corner try to do as much as you can if the first course.  Use jamb block for your corners, ones without ears on them it will make the job look nicer and they are much easier to level up as well.  You can get up to about 1 inch of height with a heavy bead of mortar under your first course, hopefully all your corners are close from your excavators work. Run 4 block out in one direction then 3 block in the other direction for your first course and then lay the subsequent courses on top dropping back 1/2 of a block in each course in each direction till you are left with one block at the top. Check your elevations frequently with your laser to be sure that all your corners are working out to be the same hieght.  It is very important that leads are level, square and plum, this will make the whole job alot easier if it is.

After all your leads are up attach your line to your line bar and pull it tight from one lead to another on the same course.  Spread your mortar down the chalk lines and start laying block, try to line the bottom of the block up with the chalk line and the top of the block with the top line.  after that course is in it gets a bit easier be sure that your block aren’t lipping over at bottom and keep running them to the top line but be sure that none of the block touch the line, stay off of it about 1/8 inch and you should be good.  Continue this process over and over till your walls are up and job is complete, also be sure to strike and brush your wall frequently to be sure that it is sealed good.  Also every two courses it is a good idea to put a layer of derwal between the courses, it is required by code in some areas.

If you are still unsure on how to do this project hire a qualified contractor to complete the job for you.  Block foundation costs are still typically cheaper than poured walls, about 30% or so and they are just as good or better in most cases because the masons have much more control over heights of corners thus leaving you a more level finished project.  And if you want you can then fill all your block with concrete thus giving you a solid block, concrete wall.  It is also a good idea to drop a piece of re-bar in every 4 foot as well and pack it in with concrete, this is also sometimes required by code.


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