Advice on building trailer deck?

-- Last Updated: Jan-11-16 11:43 AM EST --

I bought a kayak specific trailer last Summer that is an open square steel stock frame with cross bars elevated above the frame with removable yokes for two sea kayaks. The racks are a little more than 8' apart. I'd like to also be able to use the rig for hauling furniture and construction materials, and even just to have a solid surface for gear under the racks when hauling boats. So I need to build a 4'x 8' deck for it. I figure others here may have done a similar build -- what would you suggest for lumber? A "raft" of treated 2 x 4's? Those 6" wide by 5/4" thick deck boards? Severe use 3/4" plywood? The rectangular frame is about 4' wide by 6' long so 2' of the deck would be cantilevered out but supported by a single square bar in the center (which becomes the trailer tongue past the rear rack).

I would use
6" boards, treated. Leave gap in between boards 1/4" to allow for expansion.

For sure

– Last Updated: Jan-11-16 12:08 PM EST –

Don't use plywood. I would probably use 5/4" decking. Trailer deck is usually built out of 2x6 or 2x8 but I assume this will be for pretty light duty hauling. Trailer is probably not rated for much weight???? so 5/4" should be plenty strong. Haveing trouble picturing this from your post. You'll need some kind of steel/ aluminum frame around the outside to bolt these planks down to or they will warp and curl up on the ends. If you already have an undecked frame I would recommend keeping your planks inside the frame and bolt the ends down. You'll also need some cross members about 24" apart to bolt down to to keep your boards from wrapping.

Treated wood shrinks quite a bit when it drys out. If it were me I'd go ahead and but the boards together, you'll still get 1/4" or more gaps when the wood drys out. This is the way I build decks.


2nd this
Plywood won’t drain. 5/4 boards should be plenty strong without getting too heavy. You could also use expanded metal or metal mesh to keep it even lighter, but it’s nice having a smooth floor.

I built one many moons ago for bikes
If it is garaged I would just use OSB and some deck paint.

If it is stored outside, use the 5 quarters treated.

The 3/4 inch plywood will be very heavy and cost a bunch more

Jack L

Thanks, guys!

– Last Updated: Jan-11-16 12:18 PM EST –

Appreciate the advice. Since I have no garage (and no place to even build a driveway or structure: I live on a steep hill) this trailer has got to live outdoors in Western PA which means rain and snow.

SOunds like it would be best to use the 5/4 by 6 deck boards.

Ozark: would a perimeter frame of galvanized slotted angle stock be sufficient for keeping the boards from warping?

I considered using Trex synthetic deck boards but that would cost upwards of $80 or more (and weigh almost twice as much). Thought that might be more durable but wondered if vibration would cause the hardware holes in the synthetic material to enlarge and loosen if I used that.


– Last Updated: Jan-11-16 12:38 PM EST –

Trailer was home built by a good mechanic, very nicely welded and I would say pretty rugged -- but no weight rating per se. The main constraint on hauling weight is my vehicle which has a light duty hitch and is a 2.0 liter manual 6 speed (Mazda CX5). Other than boats, drywall, a few paving stones, and furniture, it is not likely to see heavy use.

trex is heavier
and tends to bend more over time.

I’d use the 5/4"x6" treated, cheaper and plenty strong for your needs.

I would also use plain old 3/16" angle. Get it from a steel supplyer in your area for the best price.


Thanks again

– Last Updated: Jan-11-16 1:42 PM EST –

I've got a great wholesale metals supplier here in town with every kind of sheet, rod, angle and tubular stock you can imagine. I try to avoid the big box stores when I can. Better pricing and service at the "mom and pop" specialists and lumberyards. We have a huge building and architectural materials recycling place too, "Construction Junction" which is on my way home from work. Worth a stop there to see their lumber and miscellaneous metals stock.

PT 3/4 plywood
for the deck, simple, cheap and fast. It will be much easier to secure to the trailer frame. It will last a long time, and be lighter then using 5/4 by 6 boards, each of which will have to be fastened to the frame, and each other. It’s what I used on my utility trailer that lives outside.

I used 3/4 plywood
Painted it, Sitting outside for 6 years, Mississippi humidity, hurricanes, tropical storms. no rot.

When it’s not in use the tongue is on a cinderblock so there is about a 20 degree slope on the deck, drainage is not an issue. When it is in use it’s moving along at 65 mph which also promotes drainage.

wood XXXXX

use steel. paint. try an online steel structural calculator

wood is a PITA


– Last Updated: Jan-11-16 7:05 PM EST –


where wood you park it ?

PTW has a catch .....New at the wood store PTW is kinda toxic

but bring it home then the PT begins absolving off the wood surface...was put on under pressure ? remember ?

so when brought home chemicals begin boiling off.

datakoll has old information
that is no longer always true.

I have marine plywood in my trailer. it was wicked expensive. But 20 years later there is no rot.


– Last Updated: Jan-11-16 8:51 PM EST –

refrigerates his wood.

First rule of PTW Industry is they lie
Second Rule: PTWI always lies.

Why ? PTWI is selling immortality thru deadly poisons for uses merely temporary at best.

Ckearly, a minor trailer use in NO WAY merits PTW.

Steel crossmembers with hemlock, yellow pine, oak planks...cover it ...a used to poer ?

Steel needs paint. I have a photo...tomorrow.

For wood, find a local mill, order, cut, stack to dry.

You are so off the mark
with your stereotypes.

gonna use deck planks
Deck planks, deck screws and galvanized bolts and washers. Cheap, simple, more than sufficient. Thanks, all.

What’s a deck plank ?
native hemlock is somewhat rot resistant.

If using untreated wood, painting the areas supported by the trailer frame with thinned linseed conditions both support and wood surface.

Blue loctite bolt n nut areas then paint exposed fastener surfaces with white Rusto.

When wood shrinks, the locktite will allow tightening the fasteners. Wood absorbs moisture, swells then shrinks when drying into smaller dimensions. Fasteners need periodic wrench checking

He is off mark because …
you keep him going.

Ignore his nonsense, and he might just go away