11ft Garden Pond Bridge

[Fast_Muchly]

Hi

I need to build a Pond bridge the total length needs to be 11ft and 2ft wide .It also needs to be flat not arched .It will be the only access to the rest of the back garden so will be used regularly.

I was thinking of using the grooved decking panels for the panels you will actually tread on as eventually we are having decking put in up to the pond .

But the actual gap where the bridge will get no support from underneath is 5ft going over the pond .It then goes over a thin strip of ground so the bridge needs to be quite long to get to a very very firm ground base .Thats why im saying 11ft .

So the question is what supports would be strong enough for this to just nail decking planks to ? .Would decking posts do at 4x4 inches or would these bow a little ,it needs to be totally rigid .

 

[big-all]

absolutly just a guess assuming the banks are 11ft apart
but i would have though your span will be nearer 13ft to allow a bit of clearence to give you a concrete footprint

would also suggest a minimum of 6x2" timbers x3 one each side and one central

as its your only access you need to make it strong enough to support any material you need to carry accross it

 

[Fast_Muchly]

No the span is 5ft

But the shape of the pond is a figure 8 style with the bridge going over the middle bit .So for the bridge to get on really solid ground it needs to span 11ft of which only 5ft is going over water .

What im asking is would 3 posts at 4x4 inches then be o.k ? .There would not be any sides on this bridge just a flat bridge with the decking paneling nailed straight on to the decking posts .Would this be enough to support anyone and last a good number of years .

Wouldnt want a heavy grannie falling in the pond thru the bridge lol .

 

[big-all]

ok simple solution place one post each end at right angles to the "bridge"

pack to stop movement lay 3 posts accross the gap place several bits of decking across at the centre
load up gradualy with 2 or 3 adults then gradualy try bouncing progresivly harder and if your happy jobs a good un
if its a bit bouncy add a forth post

 

[Thermo]

6 x 2 at that span should be ok. if you can get any extra posts neaer the waters edge then so much the better. DId one similar last year that was about 7ft, exactly the same design with decking planks, 6 x 2 and four 3 x 3 posts, one at each end in the corner.

 

[Fast_Muchly]

Im not being funny and im certainly no joiner .

But dont you 2 think that 6x2 inches is a little bit on the weak side ? .

I was going to go for 3 long posts of 3.5 x 3.5 or even 4x4 and about 3 mtr long with one straight down the middle .

Its just when i look at the old tape measure and look at 2 inches it looks awfully thin .

Alan

 

[big-all]

6x2" is far more rigid than 4x4 " and will hold a lot more weight without deflection

try bending your 12" ruler whilst holding it flat on the table

do your own calculations

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

http://www.awc.org/calculators/span...ad=5&submit=Calculate+Maximum+Horizontal+Span


obviously it depends on the type of timber but at 12" spacings its 10ft something in actual fact your at 11" centres so 8% more than the calculator shows

 

[oilman]

IIRC, floor joists are something like 7 x 2 for a 12 ft span.

The span is from support to support, not the bit over the water or soft ground, neither of those count as support (unless you put down several sheets of styrofoam).

 

[workrelatedstress]

Hello

Is there a reason why the timber needs to be small ? Its not expensive and as you mention Grannies are quite valuable.

I would stick in three 9 x 3 joists as they wont bow, wont break overkill is better ( and considerably easier ) than fishing out an elderly relative as they can get very slippery when wet !

You could excavate the ground where they hit the sides to reduce the effective height and also give you a good stable base .....

WRS

 

[Hazelb]

There was a gardening program on tv about 2 years ago, which had a different type of water feature in each program.
one was a flat bridge across a small lake/ large pond. It was a flat bridge with wooden decking planks. They spanned the bridge using 2 RSJ's, and I think ancored it each end by bolting to concrete plinths. You could google it but I can't remember the name of the program!

 

[Fast_Muchly]

Well to be honest think ive been a bit thick here dohhhhh .

When you have been mentioning 6x2 i thought you meant laying it flat but you mean having the 6 inches vertical dont you lmao .

The reason i was thinking like that tho i was wanting the bridge as flat as possible so as not to be going up a foot and over looking the neighbours garden if you know what i mean.

But i think thats the way i have to go will have to put the 6 inches vertical ggrrrr to get the extra strength .

Alan

Thanks for all the help

 

[freddiemercurystwin]

When you have been mentioning 6x2 i thought you meant laying it flat but you mean having the 6 inches vertical dont you lmao .

Don't mean to take the P but thats superb!

 

[kevindgas]

basically the height should exceed the width!

4x4 will bend very quickly and you would have a nice foot bath within a few months

the bigger the thickness the longer it will take to rot or distort

 

[breezer]

There was a gardening program on tv about 2 years ago, which had a different type of water feature in each program.
one was a flat bridge across a small lake/ large pond. It was a flat bridge with wooden decking planks. They spanned the bridge using 2 RSJ's, and I think ancored it each end by bolting to concrete plinths. You could google it but I can't remember the name of the program!

dont mean "water gardens" do you?
same 2 blokes each week, one was called mark and the other was?

just found it

if so it is sometimes on uk tv

these blokes?

bloke on the left designed it, other 2 had to build it

 

[Fast_Muchly]

When you have been mentioning 6x2 i thought you meant laying it flat but you mean having the 6 inches vertical dont you lmao .

Don't mean to take the P but thats superb!

Hmm B*gg*r Off lol .

Goes away and be's a plonker all on his own in the corner lmao