Deck sag


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Old 01-18-08, 12:31 PM
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Deck sag

I have just recently bought my first home, so by default, that makes me a dummy in some areas. When we got our inspection, the guy said that our deck sags in the middle, especially when you apply weight to the area. He gave me a tip on how to remedy that, but I can't remember for the life of me how exactly he said to do that. From what I remember, I think he said that I could take a piece of plywood (measured out to fit between the joists of where it sags) and affix that from the bottom of the deck, distributing the "give" more to the joists. Does that sound right or is there an easier method to go about this?
 
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Old 01-18-08, 12:41 PM
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MattDFreeman,

Welcome to DoItYourself.com and the Deck forum.

The LAST thing you want to use outdoors is plywood -- it'll delaminate (fall apart).

First, you need to determine exactly WHAT is sagging and what is giving when you put weight on it. May be the same thing, or it may be two different things.

Starting at the top, you have the deck boards. If they are sagged, or flex when you put weight on them (and nothing else gives), then the boards are overspanned -- too much space between the joists that the boards are attached to.

If it's the joists that are sagged, or give when you put weight on them, then the joists are overspanned.

Or is it the beam that the joists sit on that's the problem?

You'll probably have to get under the deck and pull a string across the various members to determine sag, and have one or two people walk on the deck while you're under it to see what's flexing.

Tell us what's the problem member(s) and then we can discuss the proper fix.
 
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Old 01-18-08, 01:26 PM
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At home inspections we frequently see various kinds of “creative” deck supports to deal with over-spanning problems:



What they all have in common is that they are needed because the deck was incorrectly designed and/or constructed, usually by a homeowner or “handyman”.

The big problem is that if they got something this basic wrong, they probably got other things – for example the connection to the house – wrong as well and the result may be truly hazardous.

Reinforcing the underside of the deck with plywood would IMO not be considered an acceptable repair, my suggestion is that you get an experienced deck or general contractor to inspect this and repair as required.
 
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Old 01-18-08, 01:44 PM
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Michael,

I'm very much in agreement with you. As a home inspector, there's no doubt that you have seen as much poor construction as I, as a general contractor have seen. Some of those 'owner/builder' or handyman built deck are downright scary!! But before we start calling in the big guns, lets' let Matt tell or show us what he is dealing with.

I mentioned "overspanned". We both know how common that is. But it could just as easily be rot. We don't know yet.

Matt,

If you can post pictures on a free site like photobucket or yahoo pictures and give us the URL, that would certainly be a help.
 
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Old 01-19-08, 01:19 PM
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MattDFreeman,

I would like to see pictures of the underside of your existing deck as well. Would also like to know if your support boards are 16" apart, are 2x6 or 2x8s and also, their length (span) distance.

If "under built" (re: BOT minimum code) then yes, under support system (as shown below) might do the trick. If built to code but its underside is "rotten out" then unfortunately, your existing deck could be a complete "remove and replace" fix. Without pictures of your deck's underside, measurements, etc., its very hard to recommend what is the best fix - for your specific deck.

Also... If thinking of fixing your existing deck or thinking building brand new, do remember to leave proper ventation under the deck. Many folks forget about this important need. For me, I like using white plastic lattice - private rating. The white skirt looks great but at the same time, it allows wind under the deck. Wind means the underside of the deck will dry - and eliminate rotting. For a few pictures of my different decks (and their lattice skirts with under supports), surf:
http://i178.photobucket.com/albums/w...s/100_1497.jpg
http://i178.photobucket.com/albums/w...ts/After-1.jpg
http://i178.photobucket.com/albums/w...deStairs-1.jpg
http://i178.photobucket.com/albums/w...portPost-2.jpg


Thanks for posting pictures of your deck.

.
 
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Old 01-19-08, 04:20 PM
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Spike

Nice looking job, but .... are those "shelf supports"?




If so are they listed for use as a "structural post cap" for exterior construction? The fasteners?

Normally, that connection would be made with something like:



http://www.strongtie.com/ftp/fliers/F-DECKCODE07.pdf

and would also need a listed connection to the footing - if not it probably does not meet code, and more important could be a real hazard if located someplace subject to seismic activity.
 
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Old 01-19-08, 04:47 PM
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Yes Micheal,

Those are L-Brackets under my deck. Same brackets that are used for indoor shelving brackets. For my deck, they work great. And yes, they would NOT pass code.

And I have my house deck on flat patio stones on the outside verticals and inside verticals are currently using 2x10s (as shown in the picture). In the spring, I plan to replace the inner 2x10s with flat patio stones. And yes, they would NOT pass code.

Personally, I really don't care if it passes code. When my deck was built, it was code. re: Cement pillers into the ground. After each year of frost, it was a mess. Now, our deck goes up and it goes down of equal amount. Having flat surface mount is the best design I ever used. Will it pass code? NO. But it works for me.

.
 
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Old 01-19-08, 06:21 PM
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Spike99,

Those shelf brackets JUST WON'T FLY!!

Simpson makes proper brackets for that application. Rather than construct some hazard and risk hurting somebody, do it right. The $10 to $15 you might save won't even come close to paying for a trip the the ER or the morgue!
 

Last edited by lefty; 01-22-08 at 05:07 AM.
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Old 01-19-08, 06:56 PM
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Update:

Yes Michael. You are correct. Those L-Brackets under my deck are ilegal. Nice eye.

Do you agree that "air flow" should be allowed under a deck? This was a purpose of my post and supporting pictures. Hope you agree that others should allow "air flow" to reduce rot as well.

Have a good one...

.
 
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Old 01-20-08, 09:53 AM
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Originally Posted by Spike99
Update:
Yes Michael. You are correct. Those L-Brackets under my deck are ilegal. Nice eye.
"I'm paid to be suspicious"

Originally Posted by Spike99
Do you agree that "air flow" should be allowed under a deck? This was a purpose of my post and supporting pictures. Hope you agree that others should allow "air flow" to reduce rot as well.
Airflow is a Good Thing.

The problem we see with that white plastic lattice at home inspections here in Chicago is that unless provision is made to allow a lot of movement they will crack at their fasteners, usually as they contract in cold weather.

Here's a example from this morning, at right around 0 F:

 
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Old 01-20-08, 10:17 AM
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Originally Posted by Spike99
Personally, I really don't care if it passes code. When my deck was built, it was code. re: Cement pillers into the ground. After each year of frost, it was a mess. Now, our deck goes up and it goes down of equal amount. Having flat surface mount is the best design
I ever used. Will it pass code? NO. But it works for me.
What you are trying to do there is a “floating” deck foundation, which may meet code if properly designed and the deck is not attached the house.

For example this manufacturer:




http://www.oz-post.com/html.php?p=viewproject.html&id=7

claims their system meets 2006 IRC, R403.1.4.1 under exception (3), you can watch a bunch of us attempt to hash out whether it does at:

http://www.inspectionnews.net/home_i...-footings.html

The final call would have to be made by your local AHJ.

Note that the system above goes considerably beyond what you have attempted, for example it provides for secure connection to the structure above it and attempts to secure the pad against lateral movement.
 
 

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