Deck Leaks
by David H. Pascoe, Marine surveyor
Wet beds, mildew, rust stains
in the cabinets, water stained and rotting paneling, stained
headliners, rotted deck cores with soft spots . . . these
are just a few of the damages caused by deck leaks.
Whether we're talking sail or power boats, deck leaks tend
to be a pervasive problem, one which few people give much thought to until
it's too late and the damage has been done. And as the boat building industry
keeps on turning out boats of ever decreasing quality, the problem continues
to worsen. Sometimes the leaks can be repaired, other times not.
Let's begin with the fact that nearly all boat decks are cored
with materials like balsa, plywood and foam. The coring is necessary for
several reasons, including strength. But the cores are also good heat
insulators too, and there's nothing wrong with the basic concept of coring a
deck except when water gets into it. Leaking decks usually have two basic
causes:
1. Improper design,
construction and installation of hardware.
2. Installation or
removal of hardware and other equipment by the owner.
The first thing we need to understand about decks is that the
cores must be designed to be completely water proof, followed by the rule that
nothing must ever be done to the deck to damage that water proofing. Of
course, people find it necessary to attach things to their decks, and that's
where the second basic problem arises. They drill holes in the deck and screw
things down without realizing that what they are doing is creating a point of
water entry into the core.
"Oh, but I caulked the hardware when I fastened it down,"
people tell me. Unfortunately, they don't understand several important points.
First, screws are a lousy way to attach things to fiberglass which is brittle
and will not hold screws very well. Secondly, as the screws loosen, even just
a little bit, the caulking also loosens and the leaks begin. So what they
thought was a good job of attaching something was actually doomed right from
the start.
If you own a used boat, you may find yourself the victim of
the former owner's ignorance. If you bought your boat new, pay heed to what
you should and should not do as respects adding hardware.
Those folks who build top quality boats make it a rule that
nothing should ever be attached (1) with screws, and (2) to a cored structure.
When you look at a well designed boat, what you will find is that at every
point of attachment (a) there is no core in at that point, and (b) the
hardware is bolted through the deck. This should be the inviolable rule for
both boat builders and boat owners. Never, ever, attach anything to a cored
structure. Illustrated below is the proper design and installation method of
hardware to cored structures. Notice that the deck has to be designed properly
in the first place.
Click for bigger illustration.
If the builder just ran screws through a cored deck, you've
got a problem.
Pre Existing Holes
I would venture to guess that about 75% of all boats that I survey have holes
drilled in the decks, holes that are revealed by the removal of hardware, and
holes that were never even properly repaired. Whether there are existing holes
in the deck, or you plan to remove a piece of hardware, the first thing you
must be aware of is that you just can't fill the hole with putty and forget
it. Fiberglass expands and contracts with heat and cold, so that just filling
the hole with putty won't seal it. The putty will loosen and the leaking will
begin.
If you have existing holes, or holes with open seams around
the filler, they need to be repaired immediately. But before you can do that,
you need to determine if there is water in the core. It won't do you any good
to try to fill a hole that is wet. You might as well paint your boat while
it's raining for all the good that will do. To determine if it's wet, drill a
3/8" hole on the underside: if the core shavings come out wet, you got a
problem. Now, I know some of you are going to be thinking, "Sheesh, I gotta go
through all that rigmarole just for a coupla lousy screw holes?" Well, let me
tell you what's likely to happen when you don't. A few years down the road
when it's being surveyed for the new buyer, the surveyor says, "Well, gee,
look here, there are holes in the deck and the core is all rotted and that's
going to cost $2500 to fix." And guess who's pocket that comes out of. Right,
yours!
So now that you know that dinky li'l hole in the deck is
serious business, here's what's got to be done to fix it. What you do is to
drill a total of four more holes on the under side in a rectangular pattern,
bracketing the area. You can just take a small drill and run it straight
through the deck from the hole(s) that you're going to fill to locate the area
from the underside. Temporarily cover the holes on deck with silicone sealer,
and then wait at least two weeks for the core to dry out. Once the core is
dry, then take a drill that is just slightly larger than the old holes and
drill them out to get a nice clean surface to which your epoxy paste can
adhere to. Using a nail or something similar, work the epoxy paste down into
the hole until the hole won't hold any more. On the surface, pile the epoxy up
a little to make a slight hump that you'll come back with a razor blade and
slice off nice and smooth after it has cured. It's not likely that you're
going to go to all the hassle of gel coating the finish, so you can just touch
up with a dab of white enamel. It won't look so good, but at least you won't
end up with a rotted deck core.
Railing Stanchions
The most common point of leakage is from stanchion bases. For some strange
reason, the boating industry has never seen fit to manufacture stanchion bases
that are wide enough to resist the tremendous amount of leverage that is
placed on the base by a 36" stainless steel pipe. When you lean against a
stanchion, you are likely to be placing at least several hundred foot-pounds
of pressure at the base. With that in mind, it's not hard to understand why
they so often come loose and start leaking. And to make matters worse, you'll
often find that on small boats, the rails are simply screwed and not bolted
on. And if that's the case, there's not a darn thing you can do about it
because it's just plain built wrong.
The above illustration shows the proper method of installing a
stanchion or any kind of hardware. Notice that there is no core in way of the
point of attachment, an area of solid fiberglass called a 'boss." This
eliminates any possibility of water getting into the core, and provides a very
strong point for mounting. Obviously, if your boat is not built this way,
there's nothing that can be done to change the original design.
Repairing Leaking Stanchions
Leaking stanchions can be repaired if you have some access from the underside.
Unfortunately, in most cases you have to tear the interior of the boat apart
to get that access, which accounts for the reason why deck leaks are rarely
ever repaired. The leaks just go on and on until the interior is ruined and
the boat gets junked, or some poor fool comes along thinking he can restore
it.
If you cannot reach the stanchion bolts from the underside,
it's a waste of time to try to caulk it from the exterior. No amount of
exterior caulking is going to stop the water. There is only one way to
effectively stop the leaks, and that is to rebolt the stanchion bases, and to
add aluminum doubler plates to the underside if it doesn't already have them.
It's the lack of doubler plates that is probably part of the problem in the
first place, and unless you resolve this, nothing short of strengthening the
mounting will help.
There should be no deck coring in way of the stanchion bases
but, if there is, what you have is a badly designed boat. If the core is
deteriorated around those bases, then what you are looking at is a repair job
of major proportions, and one that almost no one will foot the bill for. If
there is no core in way of the bases, then all that is necessary is to remove
the headliner or whatever is covering up the fasteners on the inside and
remount everything. The thing is, if they were bolted on in the first place,
they are not likely to be loose, meaning that what you've got is probably
screwed on stanchions. The only way to remedy this is to bolt them on. That's
easy to say and very hard to do.
Hatches
The second most common offender is improperly installed hatches which, just
like improperly installed stanchions, are extremely difficult to correct. Most
often the causes are as follows:
(1) There is not enough framing in the deck so that the deck
sags somewhat, making it impossible for any caulking under the hatch frame to
seal. In this case, you can remove the hatch frame, recaulk it, only to have
it start leaking again. The only solution for this is to drop the headliner
(if possible) and add frames around the hatch opening to strengthen it against
deck deflection.
(2) While the deck may be strong enough, the hatch opening may
be improperly designed. If all the builder did was to cut a hole in the cored
deck (as many do) and simply screw the hatch frame in place, then that is the
source of your problem. Whatever small about of deflection there is in that
deck is going to break the screws and caulking loose. Check the screws: if
they're loose and won't tighten up, then that's the problem.
Remove the frame and check if the hatch is screwed into the
core. Chances are it is, and if that's the case then it can be fixed fairly
easily. Here's the method I used for repairing a foredeck which had no frames
whatever, and a hatch that was installed through the core.
Click for bigger illustration.
My deck was very weak, so what I did was to cut two fir frames
and heavily glassed them to the underside of the deck, one forward and one
immediately aft of the hatch. Since the headliner was glued to the underside,
I opted to replace it with new white vinyl and contact cement. Took 3 hours
with 2 people.
The basic idea here is to remove the core (balsa or foam) and
replace it with a wood frame as show in the above illustration. In my case it
was balsa and I cut it all out 2-1/2" around the perimeter of the hatch,
mainly by just digging it out from between the glass laminates. Then I
smoothed off the rough inside laminate surfaces with a sanding disc. Next, cut
a teak framework to fit the perimeter of the hatch, making the frames about
1/16" less than the distance between the void space that you have created by
digging out the core. If the deck is slightly curved, you need to shape the
teak strips accordingly by planing them to the proper contour. This is likely
to be only a few degrees of arc and won't be difficult, but if you fail to do
this, it will distort the deck!
Next, fit the pieces between the laminates, set the hatch
frame in place and drill new bolt holes to size of the new bolts (instead of
screws) that you're going to use. If the headliner is glue to the deck
underside, you should bolt right through the liner, or be prepared to install
moldings to cover up the bolts. After all the new holes are drilled, you next
load the void up with epoxy, fit the teak frames into the void, caulk the
underside of the frame, and then bolt the whole mess together while
its still wet. Make sure that the edges around the new framework are
completely sealed off with the epoxy, as well as the surface of the exposed
teak.
Before putting it all together, perform a dry fit to make sure
that when you bolt the frame down that it does not distort the frame when the
bolts are tightened. It should merely squeeze it altogether, not cause any
distortions in the deck. If you did the job right, I guarantee you this hatch
will never leak again. This part of the job took about 8 hours.
Deteriorated Deck Cores
Sometimes these are repairable, sometimes not depending on where the problem
is and what has to be cut out to make the repairs. If you have, or suspect you
have, water in a deck core, the way to tell is to simply drill a couple of
small holes in the underside and see if water runs out.
The best way to repair deck cores is from the underside when
that is possible. Making repairs is easy, but putting back together everything
that has had to be torn out is where the real work comes in. The problem with
repairing from the exterior is that it is extremely difficult to accomplish a
finish repair that doesn't look like its been repaired, and it's not a job for
an amateur. If you can't make the repair from the underside, you should not
try an exterior repair yourself unless you are highly skilled in this sort of
thing. Few people are. If you can't get access from the underside, then you
have a major and costly problem on your hands.
Window Frame Leaks
A pervasive problem, window frame leaks almost invariably occur because the
structure in which the frame is mounted is weak. That usually means either the
deck below or the house top above it is distorting and causing the caulking
seal to break open. Whether or not it can be repaired needs to be evaluated by
an expert, as you don't want to waste a lot of effort and money at resetting
the frames only have them start leaking again.
One possible method of repair is to remove the frames and to
reset them using bolts instead of screws. Problem is, you're not likely to be
able to get at the inside without ripping things apart, so now what? Here's a
possible solution that will require several days to accomplish. Remove all the
window frames, and remove all the old caulking completely.
Use acetone to get it all off. Then sand the mounting surface with 80 grit
paper to rough it up. What you will do next is to apply a very heavy layer of
caulking and then reset the frame. Only instead of completely pulling the
fasteners tight, you will put 1/16" to 1/8" thick shims under the frame and
only draw the frame against these shims. This will leave a layer of caulking
that will form a gasket. After you've done this, you wait 2 days for the
caulking to cure. Then you pull the shims out and draw the fasteners tight.
What you will have accomplished here is to provide a greater
degree of flexibility to the joint surface that will permit some movement of
the supporting structure without breaking it completely loose of the seal. As
long as the fasteners are holding, you can continue to draw it tight if the
leaking continues. This method will work for good quality frames and for a
structure that is not hopelessly weak. It will only work for frames that have
flat, and not concave inside surfaces.
Leaking Port Holes
Ports in hull side usually leak because the hull side is weak and panting.
This causes the caulking seal to break loose and the frames to crack or
distort, particularly if they are plastic. Kick the hull side with your foot.
If it flutters, then you know what the problem is. You can pull it apart and
recaulk, but it will probably soon start leaking again.
Sometimes builders install the port frames with a vinyl or
fabric liner under the inside frame that causes water to wick through. Others
installed plastic frames in curved surfaces so that, when the fasteners are
drawn tight, the frame distorts and the gasket will not make a complete seal.
This can sometimes be corrected by releasing the flange or base plate. If it
springs back to a level surface, you can recaulk with 5200, but this time do
not draw the fasteners completely tight where the gaps appear on the curved
surface. Just draw it tight enough to bring the flange into the caulking so
that there is a seal. This may allow the thicker layer of caulking to flex
without breaking the seal. Then again, it may not.
Even on well built boats, as they age time will break the
caulking seals around ports. For hull sides that are fairly solid, you can use
the same method as for window frames described above.
Chain Plates
Most people find that sealing chain plates that go down through decks to be
impossible. Between the flexing decks and the stress on the plates, it really
is. Silicone and other types of caulking won't work because it won't stick to
stainless steel and its impossible to get a water tight seal. To make matters
worse, if the chain plate is bolted to a plywood bulkhead, the leaking is
going to cause the plywood to rot and eventually the rig will topple over. The
answer to this problem is to design a method that limits the amount of water
that can enter.
First of all, remember that when it rains, water is going to
run down the rigging. You don't notice this, but it does, and that's one of
the reasons so much water gets in through those tiny cracks. The other is that
the stainless bar penetrates the deck in a place where water is standing.
Click for bigger illustration.
The above illustration shows a collar arrangement that is
effective in stopping most of the leakage. The collar is made of acrylic
plastic, cut on a band or hand saw to fit around the chain plate. It is
clamped together with a screw fore and aft and serves two purposes. The
caulking gap between plastic block and chainplate should be close to 1/4" to
allow for movement.
What this accomplishes is that, first, it creates a cofferdam
at deck level so that standing water won't leak in around deck level.
Secondly, since we can't get an adhesive bond to the metal, we've going to use
a pressure bond instead by tightening the screws against the 5200 caulking
AFTER it cures. The contact surfaces of the plastic should be rough cut to
help with adhesion. The plastic is then glued to the deck with 5200, and
caulked around the chain plate. Rough up the gelcoat surface on the deck with
sandpaper or a Dremmel tool and bit. You should shoot for a layer of caulking
between the collar and the deck of nearly 1/4" thick to allow for as much
flexibility in the caulking as possible. Then, after the caulking is cured, we
come back and tighten the screws slightly . . . . but no so much as to pull
the plastic collar loose from the deck.
The nice thing about this arrangement is that if you don't get
a good seal the first time, you can always pull it up and start over, or redo
it if it starts leaking again later. Notice here that the whole idea is to
allow for some flexibility without seams opening up.
Posted October 11, 1998 (First
posted July 9, 1998 at
www.yachtsurvey.com. Page design changed for this site.)
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