DIY Network

Hello all!

My 1950s cement-block home, including the garage, is built on a slab. The exterior concrete block walls are covered with stucco. It appears as though the stucco--or what I think is stucco--was applied directly to the concrete block rather than to a steel mesh.

The interior walls and ceiling of the 20' x 20' garage are finished, so I would like to replace the garage door with an exterior wall using cement block so that it appears to be original.

My questions is this: How does one build the wall so that it is adequately and correctly "attached" to the slab beneath it, to the left and right exterior side walls, and to the "header" above? I'm not really asking this question so that I can do the work--I'm a 50+ woman--I just want to have some knowledge before I talk to contractors. I don't want to hire someone who will take shortcuts, do shoddy work, and/or charge me an arm and a leg for the job.

I have been told that the concrete blocks cannot simply be mortared or cemented directly to the slab--some type of bonding agent should be used. Also, I am thinking that rebar should be used throughout the construction so that the wall is properly secured at the top, sides, and bottom. And finally, I am concerned about a proper watertight seal between the slab and the concrete blocks. Any suggestions, comments, warnings, directions, estimated costs, materials, etc., would be greatly appreciated. I'm all for learning as much as I possibly can about this project. Hope to hear from folks soon. Thanks.

You have pretty well covered the questions related to what you want to do.

Once the overhead door frame is removed it is no problem to lay up a block wall to close the opening. Yes, I'd put small dowels in the floor to lock the bottom of the wall in place. Ome dowel near each end and then at intervals of no more than four feet in between will do that job. A seven-inch piece of #4 rebar drilled three inches into the floor should do this job. To make the same connection to the sides can be done the same way except that drilling into the existing blocks isn't quite as good as drilling into the mortar joints. The dowels can be secured easier in the mortar joints with the new mortar. The dowels at the ends can be integrated with horizontal reinforcement for the new piece of wall. The difficulty will come later because even if the new wall is carefully mortared into place the new wall will expand and contract just enough to make a tiny crack up each side and across the top. You could remove each half-block on each side of the opening and then build the new wall so that the new blocks are "toothed" into the existing wall. If the concrete blocks are already run across the top of the door opening I'd check the top corner and see where the crack is. Longer masonry walls should be provide with a contraction joint at regular intervals. There will be a crack starting at the top corner of the door opening tha goes on up to the top of the walal. That side of your infill wall can become the rest of a contraction joint. You could also look at using a reinforcing strip over the joint betwen the old and new part of the wall. This will allow the stucco to bridge the joint like drywall tape does on inside walls.

In short, filling the opening with new blocks is not a serious problem. The difficulty will be in what do do the the side edges where new and old come together.

Wow! Thanks so much for that informative reply. Your instructions re: this project has confirmed some of my thoughts re: the process of constructing this wall. I will. however, have to read it a few times before I get all of the particulars and come to a fuller understanding of it, especially the part about the contraction joints. Are you saying that a contraction joint is a crack and that cracks are supposed to be there for expansion and contraction. Yikes! I'm just not sure what you mean! I do, however, really appreciate the suggestion for "toothing" the blocks with the original walls to the left and right of the opening. That didn't occur to me!

I was wondering, too, about a vapor barrier. I feel certain that I have to have one. Would that be applied between the inside of the concrete block and the drywall? Or, should the blocks just be waterproofed on the inside before an interior wall is built?

On a sad note, I am having trouble lining up a contractor to give me an estimate for the job. My guess is that it is too small for contractors in Atlanta who have become used to building million $ homes! Thanks again for your input. And, if you are so inclined, then I would appreciate your opinion re: the vapor barrier. Again, thanks. Have a good one.

The contraction joint is as you think. It is actually formed so that an elastic sealant can be installed to make an exterior seal so that wind, water and varmints can't pass through.

In a continuous wall the blocks expand and contract as a whole unit while in a wall that is made of different separate parts the expansion and contraction is within the parts. That leads to the cracking problem I described.

As to vapor barrier, your exterior finish will provide the protection from the elements. You may want to deal with vapor moving from indoor air, into the wall to the cold side of the wall where it may condense into liquid water. In your area the periods of serious cold are few and brief. That doesn't make much of a vapor problem in the wall. Whether you include a vapor barrier depends on what the rest of the inside of the wall is made of. In your area there is more of a problem with moisture moving in from outdoors in the summer time when air conditioning is cooling the interior. Masons usually put something called weep holes in the botoms of masonry walls that lead water inside the wall to the outside. Since this in-fill wall is going to rest on the concrete floor it won't have the same drainage into the foundation that the rest of the walls have.

Try looking for a remodeling contractor. Your project is more within their area of work. A remodeler usually has the name of a couple of masons who prefer to do small jobs. The remodeler may have someone on his payroll to to this kind of work. The remodeler will also have answers based on local conditions and requirements for you. You're right that a regular contractor will see your job as more trouble than it is worth.

Hi, Jdn. Thanks for the additional information. I now have a pretty good handle on this project. In fact, I have had some fellows come to the house to assess the request and give me estimates on the project. Each of them commented on how knowledgeable I was and how appreciative they were to have a potential client who knew exactly what she wanted and how it needed to be accomplished. All that--thanks to you. I appreciate it sincerely and hope that if I have any other projects for which I have questions that you will be "around" to answer them!! Who knows--maybe I can chime in on a question that you may have!
Thanks, again.