Drainage under Deck

Reply

  #1  
Old 03-24-08, 09:08 PM
M
Member
Thread Starter
Join Date: Mar 2008
Posts: 3
Received 0 Votes on 0 Posts
Drainage under Deck

I just recently had a deck built off an existing patio and had a question about drainage. The deck is free standing (about18in. from the the decking to the ground and 7 in from the patio to the decking). Essentially there is a "whole" under the deck. 15 yards of dirt and boulders were removed. I was just curious if there will be an issue with drainage? I had three different bids and none of three contractors seemed concerned about water drainage or seteling. I live in Washington state where the soil is comprised mostly of boulders (4in to 2ft in diameter) and sand. And though it rains quite a bit, it is very dry from June through September. Anyone have any thoughts?
 
Sponsored Links
  #2  
Old 03-25-08, 05:15 AM
connie's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Oct 2006
Posts: 979
Received 0 Votes on 0 Posts
Good Morning and welcome to the DIY Forums!

Yes, you are correct, the water should drain out from under the deck and away from your house, as well.

Standing water leads to mold, termites, rot and mosquitoes.
 
  #3  
Old 03-25-08, 08:26 AM
M
Member
Thread Starter
Join Date: Mar 2008
Posts: 3
Received 0 Votes on 0 Posts
there has never seemed to be any standing water. Also the rains here are mostly misty in nature and not really downpours. Should there be cause for concern.
 
  #4  
Old 03-25-08, 01:24 PM
connie's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Oct 2006
Posts: 979
Received 0 Votes on 0 Posts
I'm sorry, did I misunderstand your question?

There should not be a hole under your deck, it should be graded to drain water away from your house. To my knowledge there is no alternative to this, regardless of where you live. Was your deck permitted and inspected? Did the inspector mention the "hole"?


Perhaps someone else will come along with another opinion, so check back again.
 
  #5  
Old 03-25-08, 01:59 PM
Join Date: Mar 2005
Location: USA
Posts: 6,130
Received 0 Votes on 0 Posts
Drainage under Deck

If you do not have standing water due to the pervious soil, grading will not have much effect.

The important thing is to make sure you have ventilation under the deck to keep the humidirt down. - Keep the sides open.

Because your deck is too low, your biggest problem will not be mosquitoes, but rot from the high humdity unless can make sure the air circulates, even with your high average humidity.

The problem is that your deck is already built.

You can always expect a low deck to have a shorter life. If the area under the deck is reasonably level or can be made to slope, a layer of 10 mil poly can be used to direct any water away from the area. Depending on the size and number of posts, there are creative ways to push (with 2x2s and stapled poly) and pull a layer under the deck that will direct most of the rainwater away, but it will not be perfect.
 
  #6  
Old 03-25-08, 03:09 PM
M
Member
Thread Starter
Join Date: Mar 2008
Posts: 3
Received 0 Votes on 0 Posts
one side is open and it is fairly breezy/windy all year round(we live on an island)so i do not foresee any issues with humidity. Also, there is no part of the deck that is in direct contact with the ground. It sits on pier blocks. Never had any problem with standing water in the area prior to building the deck. According to the city, the deck did not need inspection or permit because it was considered to be "an extension of the yard" because it is only 7in high from the patio and level with the yard around the other 3 sides.
 
  #7  
Old 03-25-08, 03:37 PM
K
Member
Join Date: Aug 2004
Location: Vancouver, Canada
Posts: 1,210
Received 0 Votes on 0 Posts
Originally Posted by Concretemasonry View Post
If you do not have standing water due to the pervious soil, grading will not have much effect.
So true. In our area, soil percolation is excellent and so landscaping to direct the flow of surface water is irrelevant.

I think the cavity under this deck will help keep that restricted space dry. I would only be concerned about earth beside the footings eroding into this hole.
 
  #8  
Old 03-25-08, 03:51 PM
connie's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Oct 2006
Posts: 979
Received 0 Votes on 0 Posts
I certainly learned something, here! Virginia soil is pure clay...it absorbs nothing without massive amounts of amendments.

A deck here with a large hole, without drainage away from the house, would be catastrophic.

Termites abound and we are constantly being reminded to remove standing water (tires, trash can lids, flower pot saucers)
because of breeding mosquitoes.

I
really should get out more, huh?
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: