Quality By Designs
We are frequently asked about how our docks
compare to other builders’.
The following are what we consider the most
important differences.
The purlins on our Docks have NO unnecessary
joints. We can transport a 45' purlin to our build site with a
special trailer built for the purpose. Most builders use 18'
purlins and overlap at a finger. While this is acceptable it also
creates a joint in the system which is holding the dock in unison across
the slips and the roof square.
The roofing also is ONE sheet on each side.
The dock is held in square and the columns/purlins vertical by the
roofing. By keeping the roofing in one sheet, we increase the
strength of the roof.
A dock with a pieced together upper structure
is subject to being destroyed by the constant daily movement. A
roof which has loosened due to excessive piecing is a more common
problem than Storm damage.
Purlins are standard for this area at 8.5x2.5
16Ga Z. The maximum span recommended by the manufacturer is 20'.
We never go more than 12'.
You will find that the largest company
building docks uses short roofing sheets spliced on a purlin to allow
easier transport of the material to the job site. This is good for
them and BAD for the customer. We build at one site within 2
Blocks of our facility and push the completed dock to your site so that
we can use the best size material to maximize the strength of the roof
for each dock size; that is ONE FULL-LENGTH sheet for each side of the
dock’s roof.
You will notice that a lot of docks have the
center truss over the header (center walkway.) The sole purpose of
this truss is to allow equal length slips. This disregards the
Fact that is 1987 this truss was the Cause of dock failures on Table
Rock. Snow drifts on roofs at the peak so this area is loaded with
more snow than any other. The downward load on the center purlin
is held by bolts which are through the adjoining columns. In
extreme loads the downward force is complicated by the outward force and
These bolts failed, the roof followed.
Wind braces are used along with box handrails
to ensure the slenderness ratio of the columns are within acceptable
range.
We have examined numerous roof collapses and
the columns are never the part that fails.
We started building docks in 1986 and have
never had a roof collapse.
Our columns/purlins are spaced at 6'.
You will find other builders with 6' spacing.
The difference is that our substructure
frames are built for the specific location in the dock. So the
Double girders across the substructure which hold the columns/purlins
parallel and vertical are ALWAYS at the columns. It is hard to
believe but not all builders do this - it is common to put double cross
girders on 4' spacing with the column/purlin spacing at 6'. This
puts most of the columns/purlins on angle iron without cross girder
backup.
Headers are built of 3/16” steel due to the
twisting action which these frames are subject to daily. ALL
joints in the frames have bolt up parts with 3/16x2" min. angle.
The fingers are a continuous set of frames with the center bolt up in
the center of the frame. This allows the wave flow to go through
the system along the fingers and carry the header along with its
adjoining frame.
The headers are not Load bearing frames.
All columns are bolted to the finger frames.
We do not use oversize holes or oblong holes
for joint connection. The frames are leveled and squared in the
shop prior to galvanizing with the holes precisely placed to match the
adjoining frames. The practice of using oversized holes or oblong
holes allows movement in the bolt up.
Movement is a dock’s worst enemy.
We have had docks hit by tornadoes.
They have never been taken apart. They have been pulled out of the
water and thrown back upside down on both land and water. The
frames have been very impressive in these cases. The roofing did
not take the “belly flop” well at all and was concave between the
purlins, leaving all other parts unharmed. The shore landing
destroyed the purlins as well as the roofing.
Lake Anchors are bolted within the frame to
assure the bolts are not the only holding part. A down Leg is used
to minimize swing and share the pull.
Ramps and Standoffs have backup cross bracing
within the frames to hold the brackets. These brackets are
1/4”-3/8” thick angle depending on the bracket type. Ramps are
light weight flexible and arched with bracing built into the end which
bolts up to the dock.