# What's the weight of an 8 x 4 sheet ?



## Losos (21 Dec 2008)

Have tried to Google it but didn't get a sensible answer :lol: I'm sure someone on here will know.

*8 x 4 Sheet of ply, let's say half inch (12.5) thick*

*What does it weigh *- I need to work out how many I can carry on a roof rack :roll: and order a suitable r/rack.


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## Peter T (21 Dec 2008)

Do what I did; buy an old Toyota Hilux.....................you can put as many 8 x 4 sheets as you want in one of those.


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## Screw Loose (21 Dec 2008)

Try googling "The density of plywood"


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## jasonB (21 Dec 2008)

depends what plywood it is, Far Eastern WBP will weigh less than Birch ply.

But this should give you a good idea.

It will also weigh a lot less as the wind gets under it so tie it down well with ratchet straps :wink: Friend of mine did it with bungee chords, needless to say they came undone and sprung down the sides of his capri leaving a nice dent in each door  

You should also subtract the weight of the actual roof rack from the total weight it says you can carry in the handbook.

Jason


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## CNC Paul (21 Dec 2008)

No Problem 8)


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## Mr Ed (21 Dec 2008)

I have done this in the past with a couple of sheets of 20mm veneered MDF. I found the bigger issue is getting them up and down from the roof, not the weight the car / rack can take.

I use those webbing ratchet straps but I still fear the board turing into a sail and detaching itself. In fact, only on Friday did I see this happen with a sheet of plasterboard on the top of a van.

If I was at work I have a book on my desk that would tell you the KG/M3 of plywood, but unfortunately I'm not and I don't commit these type of facts to memory...

Cheers, Ed


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## Steve Maskery (21 Dec 2008)

I once was driving along, minding my own business when I was overtaken by a car with a large load on the roof. He was driving quite irresponsibly and the load was bouncing up and down in an alarming manner.

I flashed him to warn him of his impending doom and got the finger for my trouble.

I was, however, gratified to find him, just a few minutes later, sat in a lay-by with his gutters (this was a long time ago) detached from his roof and the load scattered everywhere.

I was too busy laughing to return the salute.

I have carried sheets on the roof of my car. I drive painfully slowly, but it still scares me rigid. These days I let them deliver and cough up if there is a charge. It's still cheaper than damage to the car.

Cheers
Steve


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## Sgian Dubh (21 Dec 2008)

Losos":2qqtcpfs said:


> *8 x 4 Sheet of ply, let's say half inch (12.5) thick*



MDF weighs, on average, slightly under 50 lb/ft³
WBP Birch plywood normally weighs approximately 32 lb/ft³

Therefore your plywood will weigh something close to 43 lb, calculated thus:

((96 x 48 X 0.5)/1728) X 32 = 42.666 lb. Slainte.


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## Jake (21 Dec 2008)

The trouble with thin stuff like that Losos is that it isn't rigid, so the sheets bow up at the front under the wind pressure, making a nice aerofoil. I usually buy a thicker sheet of something to go on the top - it gets used up. A spare rachet over the front edge, binding the sheets together would probably help.

Rachet straps for definite. And not trying to exceed about 40mph - over about that (with my car at least) the front end gets very light and tells you to slow down.

My Thule is rated to 100kg, and I've probably exceeded that at times, given that's around 2.5 sheets of 18mm MDF.


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## Anonymous (22 Dec 2008)

a very nice trick I've picked up as a blind joiner and woodworker as well as former woodturner is when going to a contract and having materials ( friend driving me in his van) any timbers we need or plaster board etc is secured using a method such as this:

3 beams of 4x4 timber to match length or exceed length of boards to be transported, high tension strapping and then 3 more beams on the top with cross members to stop damage of timber and then a tarp to protect the timbers from rain or wind shock.

ideal when hitting the motorways etc. hehehehehehe

so its always a good thing to have that in mind if you have a pickup wagon or heavy duty trailer or something like that.

lew


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## BradNaylor (22 Dec 2008)

Not sure of the exact weight but I do know for sure that sheets of MDF, ply, and chipboard are significantly heavier than they were 20 years ago...



:lol: 


I quite often carry sheet materials on the roof of my car. Ratchet straps are essential and I also clamp the boards together along the 'leading edge' to stop them flapping about and sliding. I once had a sheet of MR MDF slowly slide out from the middle of a stack of 4 or 5 boards when I braked at a roundabout, despite my load being well strapped down laterally.


Cheers
Dan


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## Jake (22 Dec 2008)

Dan Tovey":29u7iduc said:


> I once had a sheet of MR MDF slowly slide out from the middle of a stack of 4 or 5 boards when I braked at a roundabout, despite my load being well strapped down laterally.



Oh yeah, reminds me - I always stick another one lengthways down the middle to stop that.


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## dickm (22 Dec 2008)

Trivial, but potentially expensive, tip - if you've got one of those short radio aerials like are mounted on the roof (Golfs, for example) don't forget about it as you heave the sheet of board up on to the roof rack. They snap quite easily. DAMHIKT.


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## Losos (22 Dec 2008)

CNC Paul":1e12rdt8 said:


> No Problem 8)



Paul, fantastic, that'll do me :lol:


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## Losos (22 Dec 2008)

Steve Maskery":1fjn190f said:


> I have carried sheets on the roof of my car. I drive painfully slowly, but it still scares me rigid. These days I let them deliver and cough up if there is a charge. It's still cheaper than damage to the car.
> Cheers
> Steve



Thanks Steve, nice story and shows that some people need a brain transplant.

If I do it I'll be going quite a long way so I had in mind making a kind of box the size of the sheets (and with no top) but upermost in my mind was the overall weight thingy.


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## Losos (22 Dec 2008)

Jake":1hwdq3gc said:


> My Thule is rated to 100kg, and I've probably exceeded that at times, given that's around 2.5 sheets of 18mm MDF.



My spare 'payload' will likely be around 100Kgs. too, so that's not many sheets (As you say about 2.5)

I must admit the wind thingy *does worry me *since that is a lot more difficult to calculate i.e. on any particular day the wind might be *high*, I might be driving *into it*, and going *downhill*, and if it's all racked down hard that might *still not be enough to hold it all *securely :roll:


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## Losos (22 Dec 2008)

Sgian Dubh":11pqveoq said:


> Therefore your plywood will weigh something close to 43 lb, calculated thus:
> 
> ((96 x 48 X 0.5)/1728) X 32 = 42.666 lb. Slainte.



Thanks SD 

And Dick M - Good tip, and no I'll not ask :wink:


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## big soft moose (22 Dec 2008)

for my two penneth i'd say forget the roof rack and hire a transit van - the hire will probably be less than a rack costs to buy and its much safer and easier.


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