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Old 04-01-2015, 04:17   #1
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Building a Jetty

Anyone ever built a jetty? having recently moved house we now have a salt water creek at the bottom of the garden. Its a bit muddy and the long term plan is to install a proper wall with steps. However, in the meantime I am thinking of building a jetty.

First plan is wooden posts treated with something and 3 or 4 pallets on top. How long does a wooden post last in sea water if it's treated with a good coat of fence preservative or something similar?

The dinghy is used to get out to the yacht on a mooring about 2 miles way.

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Old 04-01-2015, 04:24   #2
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Re: Building a Jetty

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Old 04-01-2015, 04:51   #3
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Re: Building a Jetty

Hi Pete

How long the timber will last will in part depend on the type of timber, if it has been sawn and what treatment you use - aka how long is a bit of string Whereever possible we used turpentine or if we were using some other hard woods we would stand the posts in old sump oil before use.

First thing that I would consider is how you are going to sink the posts into the mud. I used to have oyster farms so I think that I maybe able to help. What we used to do was to pump the posts in to the bed rather than trying to hammer them in. Not only is it a lot easier but also you do not split the timer (which would increase the rate of rot). The second advantage with that approach is that you could use alternative materials including concrete fence posts or as we did in some application sink plastic drainage pipes (remember the effect of UV on any exposed material).

We use a small motor driven water pump with ridged pipe on the end of flexible hose. This was inserted into the mud along side the posts. Some of the posts that we used were 6 foot into the mud.
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Old 04-01-2015, 05:00   #4
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Re: Building a Jetty

The idea of using water and pumping the posts in is a good one. I have a pressure washer which could be pressed into action. The mud other than the top couple of inches is quite solid an only covered a couple of hours each day at high water, so probably only need to go down a couple of feet and then set them in concrete.
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Old 04-01-2015, 05:15   #5
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Re: Building a Jetty

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The idea of using water and pumping the posts in is a good one. I have a pressure washer which could be pressed into action. The mud other than the top couple of inches is quite solid an only covered a couple of hours each day at high water, so probably only need to go down a couple of feet and then set them in concrete.
The water liquidifies the mud/sand under the post. When the water I no longer being forced into the mud it should soon return to the original hardness. The fine silt will tend to wash away leaving you with a situation similar to that of sand on a beach as the tide recedes. I don't think you will need to use concrete.
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Old 04-01-2015, 05:52   #6
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Re: Building a Jetty

Pete,

Here in the US it's common practice to use Chromated Copper Arsenate (CCA) pilings to build docks and jetties. Can you find such a product in the UK? The pilings are sold with varying degrees of impregnation of the CCA, so be certain to buy the ones specified for water immersion, not just ground contact. They will last for decades.

Jetting the pilings into the bottom with a water pump and wand is common practice for "do it yourselfers". The pros use barge-mounted pile drivers. The jetted pilings are less secure than driven pilings, but if you don't have heavy ice with tidal swings lifting the pilings in the winter, or storm surges with waves pounding the underside of the dock, this method should be just fine.
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Old 04-01-2015, 06:09   #7
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Re: Building a Jetty

My jetty was tanalised wood posts and Kreosote hammered in and dry cement and rocks filling the spaces between the tide during install. I changed some of the wood decking a couple of times.

Was fine for the 15 years I had it. North England West coast.
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Old 04-01-2015, 11:39   #8
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Re: Building a Jetty

Here in the US of A first thing I would do is consult with the EPA.
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Old 04-01-2015, 11:59   #9
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Re: Building a Jetty

If all you ever need this for is a dinghy dock, I suggest a floating dock anchored at the shore, hinged and stayed is the least work, no issues with permits (in the US); no disturbing the bottom; no surprises. Easy to maintain too. You can buy or DIY any of this. If you were choose foam as a float, use only EPS (expanded polystyrene). This is Dow styrofoam; or other rigid insulating polystyrene foam. (UC Industries of Amoco) If you encase it so that it is protected from UV it will last many years. We can often find 20, 30 or 50 gallon heavy roto-molded barrels used to transport liquid food-stuffs in bulk such as syrup. These can also be encased to protect them. Locate the screw-bung 'up'.

BTW, we call that a dock here. We think of a Jetty as a more massive earth-works to shelter a harbor or channel from the sea.
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Old 04-01-2015, 12:14   #10
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Re: Building a Jetty

Floating dock sounds good, but will likely still need some pilings to keep it in position.
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Old 04-01-2015, 14:25   #11
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Re: Building a Jetty

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Floating dock sounds good, but will likely still need some pilings to keep it in position.
If the dock is secured to the shore and the ends of the dock are stayed back to stakes on the shore with appx 45 degree cable or line, the dock will be secure. Several marinas here are built that way. Bowers Harbor places my bow over the beach and my transom in 70 feet. The entire marina is floating docks stayed to shore piles. Simply consider how you would build it if the depth was difficult.
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Old 04-01-2015, 14:49   #12
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Re: Building a Jetty

Quote:
Originally Posted by wgewaldii View Post
Here in the US of A first thing I would do is consult with the EPA.
Eek as a Civil Servant the last thing I ever do is consult another government department, it is easier to beg forgiveness afterwards rather than be refused by asking before hand. Remember the English Civil Service still thinks it runs 25% of the world Actually a couple of other house nearby have jetties so shouldn't be a problem.

We only have water for 2 hours each tide and the tides average 5 meters, the photo was taken just after HW Neaps so we don't need it to float and max depth even on a Spring tide is probably only 2 foot. The jetty also needs to be cost effective, read cheap so lots of DIY which I can do in wood.

Some good suggestions folks, so many thanks
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Old 04-01-2015, 14:51   #13
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Re: Building a Jetty

To answer you in full
YES....... use wood and deep enough to hold.
Problem will be keeping green slime off the decking in the UK...... Sand and paint and a spray weekly.

Go fer it.
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Old 04-01-2015, 15:02   #14
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Re: Building a Jetty

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Go fer it.
Its certainly a plan, or was until an hour ago and the wifey decided she wants a wood burner in the kitchen still at least i will be warm whilst designing the jetty and have somewhere to keep my mug of tea

Hud, CCA is available here for treating fencing so will certainly be looking for prepared timber or apply it myself if allowed.
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Old 04-01-2015, 15:46   #15
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Re: Building a Jetty

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Originally Posted by Pete7 View Post
Its certainly a plan, or was until an hour ago and the wifey decided she wants a wood burner in the kitchen still at least i will be warm whilst designing the jetty and have somewhere to keep my mug of tea

Hud, CCA is available here for treating fencing so will certainly be looking for prepared timber or apply it myself if allowed.
Love..
Then the requests for wood burners appear. LOL...
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