How to read construction plans

CarolinaFireJournal - Jim McClure
Jim McClure
10/22/2013 -

(Note: This is part four of a multi-issue topic.)

In the January 2013 installment, I made a comment about how cumbersome it was flipping back and forth between the large pages of a full size plan set. Well, that is what we will be doing now. I will be going back and describing in more detail two of the page titles buried within the major categories. We’ll start with the Site pages.

Hopefully you remember the Civil/Site pages have to do with the dirt itself and everything going in it. The first four of our Bond projects had missing components or something where it did not belong. One contractor forgot the fire sprinkler riser — in a firehouse! It was put in at great additional expense to the contractor. Another located a first floor sewer clean-out in the wrong location. 


This was not discovered until after the second floor was built. The real problem was not the location itself but the fact this particular clean-out was supposed to be in the wall as part of the vertical sewer pipe that drained four bathrooms on the second floor. This would have been a major “do over” except for the fact there was enough slope on the horizontal to drain those bathrooms to the next vertical pipe 30 feet away. Another forgot the water line to the island sink.

Because of these experiences, the fire department instituted a policy. We now require a mandatory all hands walk through before the concrete is poured. All trades that put something in the dirt need to be there. We walk the site insuring the size, amount and location of all pipe and conduit is correct. This applies to domestic water, sewer, gas, sprinkler, line voltage conduit and low voltage conduit. You will not be able to ensure that everything is in place if you can’t read the plans. You will have to flip back and forth between the Civil pages, the floor plans, the plumbing pages and the electrical pages to make sure everything lines up.

Highlighting each type of pipe with different colored markers makes it easier to find and follow everything.

Once the concrete cures, you rarely get to correct these deficiencies. This is why there is a picture of a concrete truck on my website.


05515 - Exit Ladder Devices
05515.A - Roof Access Ladder
07311 - Asphalt Shingles
05515.A - Roof Access Ladder 07510 - Built-Up Bituminous Roofing 07510.A - Built-Up Asphalt Roofing System
07510.B - Can’t Strip
07510.C - Built-Up Roofing Over Rigid Insulation Cricket
07510.D - Roof Walking Pad
07620 - Sheet Metal Flashing and Trim
07620.A. - Mansard Roof Cap Flashing
07620.B - Roof Cap Flashing at Low 07631 - Gutters and Downspouts 07631.A - Gutter
07631.B - Downspout
07631.D - Splash Pan
07710 - Manufactured Roof Specialties
07710.A - Roof Drain and Overflow 07720 - Roof Hatches and Vents 07720.A - Curb Mounted Roof Access Hatch
07820 - Skylight
07820.A - Skylight
10210 - Louvers and Vents
10210.A - Metal Louver
15000 - Mechanical Equipment 15000.A - Mechanical Equipment 15000.B - Mechanical Unit Condenser
15800 - Air Distribution
15800.A - Vehicle Exhaust System 16000 - Electrical
16000.G - Roof-Mounted Antenna

Speaking of concrete, there is an old Chinese proverb, “Be careful what you ask for, you may get it.” That is what happened to me on another project. The Civil engineers design and draw the concrete slopes of the driveways, parking lots, walkways, etc. They have their own language and scale to interpret. I confess I still don’t have this one mastered yet. They don’t draw to scale but compress their drawings making it difficult to understand whether the pitch of the driveways is too steep or too flat. The numbers are more important than the lines. One of my early remodels involved new drainage and concrete for the parking lot behind the station. The old surface did not drain well and we often had a lake after a heavy rain. I shared this with the engineer. His design solution was not apparent to me until the concrete was being poured. There were more ups and downs in this parking lot than a skateboard park. Kind of made it hard to play any sports requiring a round inflated ball.

The first firehouse project I was assigned was in 1997. It was a drive through station with a sweeping 180 degree return driveway. The concrete floor of the apparatus bay and living space was poured first leaving the ungraded soil for the driveway. I was new to all this but the pad looked too low to me. I expressed my opinion but as the new guy I did not carry much weight. The contractor and his sub-contractor assured everyone that it was fine. The city staff and the architect did not pursue this. Why this was important was the design called for all the water to flow out the return driveway. The distance had to be at least 150 feet from the back apparatus bay doors to the gutter.

Flash forward 12 months and the building is now open. The first rain we get and water is rolling in the back door from the driveway instead of the other way around.

I’ll give you a moment to think of some solutions for this problem. Did you think we could lower the driveway? That wouldn’t work. There would not be enough “fall” to get the water to flow all the way out. How many thought we should raise the apparatus bay floor? That would reduce the apparatus bay door height, create a trip hazard and decrease the functionality of the building. How many are ready to hang the contractor in the hose tower? A satisfying answer but it won’t solve the problem. The solution was to cut the concrete driveway right where it meets the building. A trench was created for a French drain with piping running all the way around one side of the building to the street. That mistake probably cost the contractor his new boat.

Bottom line — the dumb firefighter was right. They had cut too much dirt from the building pad and it was not high enough. If I knew how to read the civil plans then I might have made a better argument.

Let’s jump to the electrical pages for a second. If you are checking to see if the four inch conduit is coming up right against the wall in the communications room and it isn’t, it might have to do with the concrete under that wall. That will send you to the Structural pages to see if the wall in question is a bearing wall and has a wide footing under it. This will force the conduit off the wall at least six inches, totally screwing up the layout in the communications room. You have to communicate early in the process to the design architect, structural engineer and the electrical engineer what you need so they can coordinate everything. Once the structural engineer has their say you may be too late. This page flipping exercise will occur again and again as you review your plans.

I told you we would be flipping pages. Let’s go to the roof next.

The purpose of the roof is to keep the building and its contents —including you — dry. Mother Nature’s job is to keep on being Mother Nature. This means we have to think about the roof for as long as we spend time in the firehouse. A new roof is like a walk-off home run in baseball. It means very little the next day. You start all over again worrying about the next event. My intent here is to make sure you know enough to get the best roof you can for your meteorological needs. Some of us are challenged by snow loads and ice dams, others by 140 mph winds and wind driven water. Still others worry if the roof will come down in the next earthquake or off in the next tornado. There are specific building codes in each part of the country to deal with all these events. None are guarantees but are designed to mitigate the damage to the building and you need to be familiar with them. The simplest example I know is roofs in snow country. A roof with a 12:1 pitch will shed its snow more quickly than a 4:1 pitch and a flat roof had better be engineered for the potential load.

Once we know the roof will hold up, the next consideration is; will it drain? Obvious on pitched roofs, not so obvious on built-up roofs. It does not take much slope going the wrong way to create a ”birdbath.” A birdbath is a low spot in any flat surface that holds water where you don’t want it. Standing water will eventually find its way into your building and you can take that to the bank. One of my project managers would always have an inspector on the roof when the roof was being done to make sure it worked as advertised. The first thing he would do when it was finished was to pour water over it to check for birdbaths. If you do not understand what the roof plans are telling you, ask the architect to explain it. If you do not know what a ”cricket” means to a roofer find out. Ensure that there is enough pitch to get the water off the roof.

While we are on the topic of flat, built-up roofs, there are different types of material for roofs. There is the built-up roof made with tar paper, hot tar and gravel and the new single ply membranes sealed at the joints. The new stuff seems to last longer if done right. One critical element; once that membrane is down, you must minimize foot traffic, tools and dropped nails on the roof. All it takes is one nail dropped and then stepped on to puncture the membrane.

Once you get the water going in the right direction you have to pay attention to the rainwater leaders. These are not alpha-type raindrops. It is construction speak for a downspout. If you live and work where water freezes you do not want the runoff flowing across your path of travel. If trees surround your building you will have leaves on your roof. They will eventually clog the gutters, downspout or the collection point on a flat roof. You will not notice it until the water starts dripping through the ceiling right on the captain’s computer. True story. Aside from doing proper and timely maintenance you need to “daylight” you rain leaders. Spec a break before the pipe hits the concrete. Do not let the architect design a system where the pipe disappears into the concrete. Ask for a drain with a grate over it with the leader stopping several inches above the grate. By the way, checking out this particular detail will also have you flipping to the architectural pages that show the exterior elevations. If it is raining and no water is pouring out you will not have a clue there is a problem until it is too late.

I don’t know about your departments but ours train firefighters to “throw ladders.” Sometimes we use our own building for ladder training. Make sure your architect knows this and designs accordingly. Throwing a ladder against a nice aluminum fascia will ruin it, the fascia not the ladder.

Shown in this article are the keynotes to the roof plan and a partial roof plan. It uses the CSI (Construction Specifications Institute) numbering system I spoke about in my first article.

This shows a combination sloped roof with a flat roof in the center. The flat roof creates space for the HVAC, access ladders, vent pipes, walking pads, etc. The dotted lines indicate the exterior footprint of the building. Other notes on the Roof page talk about locating penetrations to avoid the sloped roofs, attic ventilation calculations and notes regarding the different down spouts.

Look forward to bringing your more information in the winter issue.

Jim McClure is the owner of Firehouse Design and Construction (FD&C). The mission of FD&C is “to help firefighters, architects and government agencies design and build maintainable, durable, and most importantly, functional firehouses.” McClure’s career in public safety spans almost 29 years. For more information visit, or call 408.603.4417.
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