Water Pooling under decking! Help

Soldato
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Our builders have built a frame for the decking sittting on plastic sheeting

over night rain have come back to pools of water collected on the plastic all touchiing the wooden supports

I am assuming this will rot the wood over time if allowed to collect after every rain

Is it ok to make holes in the plastic to allow drainage or does that risk weeds growing up?

any other ideas?
 
Soldato
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Surely this won't be much of an issue when the decking is complete? The decking planks would allow the rain to run off the sides.

I thought they used more of felt type material under deckings anyway, stops weeds growing through, but allows water to seep through.
 
Soldato
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the water will still run in the gaps and gather..

I wasnt sure about felt/ membrane or other but the builder says hard plastic is normal
 
Soldato
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There are no concrete posts

Half the area is sitting on concrete drive way

Other parts is attached to the house

Rest is just on supports on the grass.

I'll get photos
 
Soldato
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double post
IMG_20180921_094423.jpg
 
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Soldato
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PS - here is my 4.8 x 5.8 decking build that I finished last month. I used a mix of posts concreted into the ground (10) so that there would be no lateral movement, it was attached to the brickwork at the back, and I used 30 adjustable decking supports which sat on concrete slabs, so every individual beam had at least one support in the middle as well as by the frame.

 
Soldato
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On the grass?
yes

the right hand side is sitting on concrete
bottom is attached to the house
top left is sitting on grass

1) is that ok or does it really need a contrete post top left?

2) how to deal with the water pooling around each leg post as the ground is not flat?
 
Soldato
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someone else has suggested just poking lots of holes in the plastic to allow water drainage and then lay membrane on top to stop weeds/letter water run away.
 
Soldato
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I'm no expert - I only know what I've seen in Youtube videos showing how to make decking. But that doesn't look right to me.

Is this a professional who's doing this? Only I've never seen it done like that. The water is going to pool around the posts and it will easily sink into the grass. The end of each of those long beams should be concreted in posts. Any support sitting on grass should be on a slab.
 
Soldato
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Yes he is a professional

doing some research some people say its fine as long as the weight is spread over a larger area, which it is.

thank you for your help, much appreciated . ill keep researching
 
Associate
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Weed fabric isn't always necessary but does provide that extra protection. Plastic sheeting is the wrong material really as you want the wooden supports to avoid prolong contact with water. As the plastic sheets will pool water rather than allow it to pass through the wooden support will decay faster than normal. If you use weed fabric, it needs to be permeable.
 
Soldato
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Agreed, he's used a DPM sheet there.

If those vertical supports are sitting on top of the DPM (presume so), they will suck water up the endgrain. Guessing he hasn't treated the cuts in the timber either?

Infact, is that even treated timber? It's hard to tell.
 
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