Building Homes or Extensions/Header design

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Expert: - 4/26/2010


Question
Looking at retro-fitting into an existing 13' tall block wall (blocks 4" high / 8" wide) a 7' x 9' wide single garage door.  Thinking about cutting in on both sides and adding angle iron then weld angles together in the middle. Would you know size of angle iron for this job or a better way?  The wall is a non-bearing side wall (trusses run parallel to it) yet would have 6' of block above header to support.  Thank you, Eric - AZ

Answer

lintel reinforcement
Hi Eric, that seems an odd size for blocks 4x8 but anyways, you are on the right track.  The lintel or header support is the most important the side angles not so much.  Most masonry walls are self supporting at the header.  In order for the top blocks to fall down the sides must be able to push out otherwise they will remain in compression.  Think of the kid's game of picking up blocks of wood with other blocks of wood.  As long as you are pushing from the sides the middle blocks won't fall down.  As soon as you let the pressure off from the sides the middle blocks fall in.  The same is true with masonry, as long as the sides of the opening you are creating have enough mass to keep from spreading from the weight of the header your masonry won't fall in.  That's not to say that you won't need to install a lintel support angle as you have suggested.  First of all, make all your cuts.  Try not to over cut your vertical side cuts into the header area, however, you can overcut your horizontal header cut on both sides.  In fact I recommend overcutting by at least four inches on each side this will give your lintel angle something to bear on. I would use a 4"x6"x 3/16" steel angle for a 9 foot opening.  I am attaching a simple drawing showing two types of lintel reinforcement. The top drawing is for installing a steel angle.  The bottom drawing is for installing a precast concrete lintel.  I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson

Bruce E. Johnson

Expertise

I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.

Experience

Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

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