I've been asked to build a decking area which will overhang a pond, the decking will be 8 mtrs x 6 mtrs, the overhang will be between 700 mm -1000 mm roughly. I won't be able to put any supports under the over hang as it is directly over the pond and it's very marshy/ soft ground. Any recommendations on the size of joists I should use to make sure there is no bounce on the over hang?
structural engineer job perhaps ?? maximum span normally 600 so a 700m over hang possibly 9x3" cantilevered with perhaps3-4m off weight to counteract
9 x 3 was what I was thinking, and there would be a good 5mtrs of weight counteracting on the opposite side, question is am I brave enough to try it, do I involve a structural engineer or take joinerjohn1 advice.
Run a beam as close to the waters edge as you can and 8x2 at 400 centres will be more than enough, another beam at the back edge 4.8 and one in the middle, screw all your joists down in to your beams, through the side.(skew) If you can, run up some 45s from each post holding the beam to the joists, you can also run your boards at 45 degrees to your joists rather than at 90 degrees, which will add strength. Stick a rim plate on and some noggins. With the weight of the joists and decking its not going anywhere
That looks like the jobby, although my job is not that high of the ground probably about 500-600 mm so I wouldn't be able to get the 45's coming up of the posts, so i could drop a few smaller posts at intervals under neath the main support beam.
I researched this years ago and tend to go by a guide of max of 25% of joist length, there are obviously variables in that, google cantilever decks and go to images
Bear in min d that the end posts will be taking a much greater proportion of the deck's weight, so its founds need to be able to take it and not sink. Any possibility of adding some diagonal support struts - like on a gallow's bracket - coming from the bases of the end posts up to the end of the decking - that should strengthen it lots and cut down on any possibly bounce?
For me, I'd want to have the last 3 metres, smaller joists(or lower) and double up the decking boards all the way out, staggering the long joints. Mr. HandyAndy - Really
Forums
Facebook
Twitter
You Tube
Instagram
Shop