Trickle Down Arch Design

Our latest design challenge is a brick arch with recessed accent courses that tie in to the recessed accent courses of the running bond of the building.  Here is a building in Baltimore with a similar style arch.

What complicates the matter further is the 32" soffitt and the question of how we will prefabricate the arch.  When designing a normal radial brick arch the measurements that we need to determine are the circumference, angle, length of the outside arc, and brick size.  

circumference x angle  =  length

360    

But in this case the masonry opening arc is half round and the outside arc is elliptical.  Also we are limited by the size of brick because the joints of the accent course must line up with the running bond.  Here is where it gets tricky.  Instead of starting with the arch, I started with the running bond and accent course, and started at the top of the arch.  To pass the eye test the arch cannot be too tall in the center, but also the 2 1/4" brick size must line up to the same number of courses in the arch.  The only way to get the desired effect was to start with 3 5/8" closure size brick towards the top of the arch, then work our way smaller towards the bottom.  This is how we came up with the ellipse.

I am no math wiz, so if anyone knows a better way to reverse engineer this thing send me a message.  What has me mixed up is the length of the elliptical arc combined with the size limit of the radial segments.  

You say Palladium, I say Palladian

A palladian window is a large window divided in three parts: a central sash that is arched at the top and two sashes on each side of it that are smaller than the central sash; the smaller sashes are rectangular, topped with flat lintels.  This style of window is also called a palladium window depending on where you look on the internet.  Needless to say, this window is very common in the D.C. metro area with some of the production home builders like NV homes, Winchester homes, Pulte homes, and Toll Brothers.  The challenge for a bricklayer is how to cross over this style window with a brick arch.  Cast stone commonly is used.

Here is a palladian surround we did for Plus One Masonry @ Pulte homes.  As you can see the lines are clean and the look maintains it's colonial architecture.  There are several examples of historical palladian/colonial buildings in Annapolis Maryland one of which is the Hammond-Harwood House

And a modern example in Baltimore is a multiple building project at Johns Hopkins University for Henry J Knott Masonry.  Here it is 3D google maps.

Getting back to the residential palladian window, here is the design we use for a brick arch.  There are two  tricks to making it look good in my opinion.  First is how the radial arch and the lintel jack arch come to a natural meeting point on each side of the 1/2 round window. Second is to avoid small brick pieces if possible.  You do this by starting with a 7" long radial brick, and by the time you are to the 5th course on the 1/2 round center, the bonded arch meets up with the bonded lintel wing.

My vote is for calling it a palladian window.

Prefabrication: material cost vs. labor cost

    I was trying to come up with a formula for masonry contractors of how to quantify in dollars how utilizing prefabricated brick arches saves money.  Like a profit & loss statement there are fixed numbers and numbers that can manipulated.  We are doing a job right now for LFJ masonry called Watkins MOB in Virginia.  We have prefabricated and delivered 86 brick arches.  Eusebio Cantone of LFJ told me that when they estimated the project they added the price of the arches to the material costs and subtracted estimated production time in hours from their take-off.  He said:

     "The largest benefit is that we can set these and keep going, we don't have to wait! At the end of the day you can figure the total time you took to fabricate the arches (man-hours) and that would be your time savings on the project. Based on crew size and number of arches on the project you could also determine the following, the project saved X number of man-hours to fabricate and set arches therefore saving X number of days on the total project and that is where equipment savings comes in as well."

I figured we used 8 diamond blades, cut over 8000 brick, purchased, cut and bent 3500 feet of #4 epoxy coated rebar, 20 boxes of wall ties, and purchased and mixed 800 bags of cement/grout.  We also dedicated 2 employees to work on this project for 100 days each.  This does not take into account utilities, fuel, transportation, and maintenance.  Other costs that are sometimes overlooked by contractors that are reduced by installing prefabricated arches are rental equipment, employee insurance and liability.

So here is the math that gives you more profit:

$ INCOME

- $ ARCHWAY SYSTEM PREFAB

= X

+ $ SAVED IN LABOR HOURS 

+ PRODUCTIVITY ( $ FROM DAYS ON SITE)

+ MATERIAL NOT PURCHASED (REBAR, CEMENT, WALL TIES, ETC.)

+ EMPLOYEE LIABILITY

+ EFFICIENCY (ON TIME DELIVERY, START THE NEXT JOB SOONER)

+ RENTAL COSTS AND MAINTENANCE FEES SAVED

= MORE $$$$$$$$$$$

The hardest thing to put into the equation is efficiency...lets say LFJ masonry finished this project 20 work days ahead of schedule, how do we add a dollar amount to the equation.  In reality that same masonry crew can complete more jobs in a given year, therefore increasing revenue.  I think efficiency would be a % that carries over to the revenue for the year on the profit/loss statement.  

Thanks Seb.  When I take some pictures of the finished buildings I will be sure to post them.  

Post Tension Brick Jack Arch

We are currently prefabricating 8 foot long brick jack arches for a project in Philadelphia that have no angle iron support under the brickwork. Oh the joys of design-build. Actually it has given us the chance to try a system that Ray Wethington invented, of using post tension #4 epoxy coated rebar through he length of the arch.

Post-tensioned is the descriptive term for a method of applying compression after pouring concrete and the curing process. 99% of the brick jack arches we prefabricate are set on steel angle irons, and it is the steel that carries the load of the weight above the masonry opening. We do make structural jack arches but code usually dictates steel reinforcement unless a historical variance is given.

For this job we are drilling a 1" hole into the brick before we prefab the arch. Then we are inserting the rebar that has a hook on one end and threaded on the other end. We then tighten a nut on the rebar threaded end giving the brick jack arch post tension strength. The dramatic effect is 8 foot straight spans with brick and joints visible from below.

Brick Arches of the Roman Colosseum

Walking up to the Colosseum through the modern streets of Rome with my wife Brigid made me feel alive. I felt proud to work for a company that designs brick arches because there is no greater proof of masonry’s mastery than in Rome. I also felt insignificant in the physical and historical scope of the Colosseum. The stories of thousands of people who had died and cheered on the spot I was standing are what movies are made of.

The exterior of the Colosseum is made from white travertine stone that was quarried from the local hillside and held together with iron clamps. I was surprised to learn that all of the interior was brick and mortar. I we walked through the arcades and hallways, the tour guide gave a short talk on the significance of Roman technological breakthroughs in the field of masonry. The Romans discovered that masonry strength was not compromised by adding arches to span openings. The strength of the masonry structure increases as weight is dispersed above an arch.

The structural brick arches of the seating areas held up as many as 80,000 people as well as the weight of the masonry above it. The arena itself has a brick underground structure that allowed for trap doors with people and animals below like in the movie Gladiator. The brick jack arches of the arena and ground level doors were brilliantly designed and built.

Using four foot long brick, the Romans constructed the jack arch for functionality. The jack arches that supported the arena floor have a 77 degree skew but the jack arches under the massive seating area are built with a 70 degree skew to support more weight above it. What a marvel of engineering.

Chevron

Wikipedia defines a chevron as a v shape pattern. We see this in nature with Canadian geese flying overhead. In my case it has to do with architecture, in particular with a herringbone brick pattern.



This is a custom design of a firebox with a herringbone pattern. The architect wanted to replicate a slate fireplace with 1" x 6" brick shapes. The bond works out to 1/5 with a 1/4" joint. As you can see in the following picture, there is a central chevron in the back panel of the fireplace, and visually the firebox has 3 chevrons pointing up on the back panel, and 3 chevrons on the side panels.



This firebox is pleasing to the eye, but a real pain in the but for the bricklayer to layout. I hope to post some pics of the finished fireplace soon.