Shelter Build Series 1
14 x 50 foot extended length shelter
Seven courses of blocks are started. You can see the longer wall pieces of rebar tied to the floor tie-ins. Note the corner boards that ensure the corners are plumb and square. Also, see the blocks shaped like a “U” stacked up – they are bond blocks that allow for horizontal rebar to be installed. Every other course is made from bond blocks and has a run of horizontal rebar.
This is a rough opening for a flat blast hatch that will allow access to an adjacent generator room. They’ve used a masonry saw to cut blocks in half to create the rough opening and a steel beam for a header.
This is the completed rough opening for the 36 x 80 inch blast door. Note the cut blocks on each side. The left side has them every other course, the right side has them every course. A masonry saw makes quick work of cutting down blocks.
The 11 courses of the walls are complete and the wall/ceiling tie-in rebar is sticking up. The rebar in the ceiling will be tied to these pieces. The rough openings for the blast door and generator room blast hatch are shown. Note how much space there is with the 14 foot inside width. Prefabricated shelters must be under 10 feet wide – or they have to get expensive wide load permits for delivery.
The ceiling trusses are being set. These wide flange beams will stay in place to reinforce the ceiling slab. Beams are a much more efficient shape to carry loads than the round shape of rebar. Note the holes punched in the bottom of the beams for the longitudinal runs of rebar. Located at the bottom of the ceiling slab, this rebar will be in tension if the shelter has to adsorb a blast load.
The trusses are centered between the walls with angle brackets bolted to the bottom of the beams. The same brackets are bolted to the ends of the beams to hold the form boards for the ceiling in place. We provide all the brackets and their fasteners in this kit and the trusses have all the holes punched for these brackets.
In this view of the truss centering brackets you can see that the brackets have holes in one end and slots that are plasma cut in the other end. The slots allow you to push the bracket tight to the wall so the beam can’t shift when you are pouring the ceiling.
The trusses and the brackets are factory primed to inhibit rust.
The top view of the trusses and ceiling form boards. Note the intake ventilation pipe next to the riser blast hatch in the back of the shelter.
The NBC filter will be at the back of the shelter and the outflow vent pipe will be at the front by the blast door so that the filtered air will have to transit the entire protected space before it is returned to the outside. This will ensure that oxygen is replenished and the carbon dioxide and water vapor that the occupants exhale is relieved throughout the shelter.
You can almost see the slope from one side to the other of the top of the ceiling in this picture. A perforated drain pipe will be laid in some river rock at the base of the shelter on the lower side. When everything is backfilled, any surface water that finds its way to the top of the shelter will run to the low side, down the wall, and into this drain.
The Generator Room
This is a generator room adjacent to the main shelter. Special care must be taken to ensure that carbon monoxide or fuel vapors do not migrate into the shelter or accumulate in the generator room.
Generators should have their own air supply and have the exhaust pipe routed outside. If the generator is going to use filtered air from the NBC filter in the shelter, the air consumption of the generator must be factored into the total air supply needed. Generators with exhaust pipes routed outside are air pumps – they take air from the shelter and pump it outside. This can make the shelter go negative pressure, relative to the outside air pressure. This is exactly opposite of what is needed in an underground shelter which should always have positive relative pressure (overpressure).
American Safe Room supplies parts in kit form. It is the responsibility of the installer and occupants to ensure that no carbon monoxide or fuel vapors enter the shelter or accumulate in a generator room.
The walls are up, a bottom form board has been put down for the ceiling and the rebar has been placed. Temporary cribbing is inside to hold the concrete until it cures.
Note the extra course of blocks on the shelter next to the generator room. These will be filled with concrete when the generator room ceiling is poured to form a parapet over the exposed end of the shelter.
Sealing the Outside of the Shelter
The Critical Components
The ventilation pipes are bolted down to the bottom form boards with a heavy duty gasket. Just under this vent pipe is a ceiling mounted blast valve that has the same mounting flange and uses the same bolts to hold it in place. The nuts are on the inside in case the blast valve has to be removed for servicing. The vent pipes get poured in place and backfilled.
Also shown here just behind and to the left of the ventilation pipe is a one inch penetration. It is also bolted down to the bottom form board with a gasket. Penetrations carry water, electrical lies, data lines, or septic removal. We have one inch, inch and half, and two inch ceiling penetrations available – see section G of the shelter kit manual for more information about ceiling penetrations.
The riser blast hatch is bolted down on the riser truss pair. Right below the mounting flange at the bottom of this hatch, you can see the channel section we weld between the trusses. The rebar is cut so it butts up against this channel section. These channel sections and the trusses are forms that make the penetration hole for the hatch.
To the left of the hatch are two more one inch penetrations.
The optional single leaf blast door is mounted on the exposed end of this shelter. It allows easy access for people, pets, and equipment. The door and frame are come all assembled and are bolted to the wall before the steel door leaf envelope is filled with concrete.
Note the grease zerks on the ends of each of the hinges. They also feature oil impregnated bronze sleeve bearings so the 1,700 pound filled weight of the door takes only 20 pounds to open or close.
This blast door has the inset deadbolt assembly and wide angle viewer options.