# Newbie needs to build a deck addition



## Willie T (Jan 29, 2009)

Buy one of those Deck Building books Lowe's and HD sell. They're really pretty good.


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## toolbot (May 6, 2011)

Yep, I bought one of those as well, and contains a lot of good information I will be using.


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## toolbot (May 6, 2011)

Really would appreciate advice on post/beam locations. Have gone through several books now, but would like input from people with real experience.


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## BigD9 (Mar 10, 2011)

I did almost the same thing you are wanting to do. I got Lowe's to design it as close to the design I wanted and then I modified it from there to fit exactly what I wanted. That way it gave me the post size and spacing. Then my next door neighbor, who thinks he knows everything about everything, came over and told me I was doing it all wrong. I was way over-building the deck and wasting money. I knew at that point I was doing it properly because I've seen his work!

Don't forget the permits if you need to get then in your area.


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## Ron6519 (Mar 28, 2007)

You have so many direction changes on this structure. Where it meets the old deck I would put a row of supports a few feet away from the old deck and cantilever the new deck into the jogs. 
Two supports at the end.
Row of 3 supports midway between the two ends.
Another few along the curve. The number depends on the radius of the curve.
Ron


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## toolbot (May 6, 2011)

I just finished doing a mockup in SketchUp, thinking that I have the foundation covered, but I am definitely confused when it comes to the joists and decking. I'm not sure how I would create joist headers so close to the pool, so I can put down the decking without running into stability issues. Here are a couple of views:

http://www.dropbox.com/gallery/22475563/1/deck?h=b4efc8

I know there a couple if issues, but please take a minute to let me know of any major issues. The books are a little help, but not enough in this scenario. It's a stand alone deck, using 16" off center joists, and 5/4"x6" decking.

I was told 12' is the longest lengths I should order for both the 2x8's and the decking, so that's what I used as the largest lengths.

Thanks!


edit: Didn't see your suggestions until I already finished the drawing.


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## Ron6519 (Mar 28, 2007)

The arc around the pool would be a continuous beam, not a bunch of hurdle like supports. The beam would link the support posts together.
Ron


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## toolbot (May 6, 2011)

That's what I thought as well, but I am having trouble figuring out how to do this, and the book didn't seem to cover this.


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## dpach (May 12, 2009)

Please make sure to get a copy of the local building codes for your city. Books have very good ideas, and cover the basics, but you must have joist spans, beam size and methods, post spans (depends on type of beam/size of beams you use), joist size (2x10, 2x8 etc), etc that meet your local code. You will also need to find out the max distance between joist braces (braces between the joist for lateral stability) and this can also vary from city to city.

I built my new deck last summer (have to add railings and stain this summer) and found very good advice online by googling. But I found out a lot by speaking with the city's building code/permits office and building inspector. For example, books say to dig footings/piles to below the frost line. My local codes call for minimum 8 feet and strongly recommend 10 feet because I live in very gumbo type clay where frost puts so much side pressure on footings that frost heaving can suck the footings up (and leave a holly below the footing). By going 10 feet I would have 4-5 feet below the frost which would stop this heaving due to side pressure. I went 12 feet.

Another example was local codes called for minimum 4x4 posts, but local inspector recommended 6x6 because as wood dries and ages, it can get vertical cracks up the posts lengthwise. He's often seen 4x4's with cracks on each side that have actually met in the middle of the post, where as 6x6's would rarely ever have this happen. Plus your footings diameter will depend on depth and also post size (wider post requires wider footings).

As already mentioned, make sure you have a permit. It not only covers you and future issues, but it allows you to speak with a permit writer who will give you some very good info.

One other tip for later, I strongly recommend spending the $300 or so to blueskin (or another brand of barrier) the tops of the joists and beams. The most common cause of joist failure is where the deckboards get screwed to the joists -- rain sits under the boards on top of the joist and soak into the screw holes. That is the most common cause of joist rot. This membrane is rubber surfaced with a tar based compound under it that seals around the screws as they go into the joists. Its a pitty to see someone tearing down a deck because the joists fail in 10 yrs.

Good luck!


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## Ron6519 (Mar 28, 2007)

toolbot said:


> That's what I thought as well, but I am having trouble figuring out how to do this, and the book didn't seem to cover this.


Books don't cover every contingency possible. This would come from experience and sometimes professional guidance.
I would place posts every 4 feet or so. The middle posts would be 6x6's. The ends, 4x4's. Since the beams will hit the posts at various angles, you could notch each post so the beams would have a flat surface to bolt to the post.
I'm sure there are other ways to do it. Others will come along and make suggestions.

Ron


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## Daniel Holzman (Mar 10, 2009)

Ron, I am assuming that is a typo, you don't mean to place posts every 4 inches? Probably every four feet? Even so, posts every four feet are almost certainly well in excess of code requirements. As previously noted, get the code guide for your area. When I built my deck, the building inspector gave me the "Prescriptive Residential Wood Deck Construction Guide", based on 2006 International Residential code.

This was a very useful guide, included most of what a person would need to build a deck, including post sizing (6 inch minimum in my town), connection details, nailing, screw and bolt requirements, joist sizing and spacing, footer design, staircase requirements, railing details, bracing, and a few other critical details. You have an unusual shape, however the post spacing, joist and beam sizing is primarily a function of the tributary area of deck supported by each joist or beam, and once you know the required load per square foot it is relatively easy to determine the required joist size and beam size, and minimum post spacing. Then you can play around with your software, move the posts etc. to maintain minimums.


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## Ron6519 (Mar 28, 2007)

Daniel Holzman said:


> Ron, I am assuming that is a typo, you don't mean to place posts every 4 inches? Probably every four feet? Even so, posts every four feet are almost certainly well in excess of code requirements. As previously noted, get the code guide for your area. When I built my deck, the building inspector gave me the "Prescriptive Residential Wood Deck Construction Guide", based on 2006 International Residential code.
> 
> This was a very useful guide, included most of what a person would need to build a deck, including post sizing (6 inch minimum in my town), connection details, nailing, screw and bolt requirements, joist sizing and spacing, footer design, staircase requirements, railing details, bracing, and a few other critical details. You have an unusual shape, however the post spacing, joist and beam sizing is primarily a function of the tributary area of deck supported by each joist or beam, and once you know the required load per square foot it is relatively easy to determine the required joist size and beam size, and minimum post spacing. Then you can play around with your software, move the posts etc. to maintain minimums.


 I'd put the posts that close because he was going around a curve and it would let him get the decking close to the pool without added framing between the beam and the pool.
Yes, it was 4 feet.
Ron


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## toolbot (May 6, 2011)

Wife tried to pick up a copy of the building code for my town, but the code inspector told her to just have me come in with my plans and he will go over it with me. Of course, it doesn't help he is only there when I am at work, and while I can find the building code for fences etc online, nothing for decks :/

It looks like the type of footings I used in my drawings are outdated, and known to have problems with moisture. dpach's pictures/deck look pretty good. I guess I need to go buy a more recent book and read up. Are there any other resources for this kind of project?


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## dpach (May 12, 2009)

Here's a couple on basic footings:

http://www.deckmagazine.com/pdf/2007/0701/0701pier.pdf

http://www.finehomebuilding.com/PDF/Free/021180044.pdf

Don't know if they'll help you a lot, but some good basic info. www.deckmagazine.com also has various forums that discuss design, structure, etc specifically for decks.


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## SteelToes (Oct 5, 2010)

_For example, books say to dig footings/piles to below the frost line. My local codes call for minimum 8 feet and strongly recommend 10 feet because I live in very gumbo type clay where frost puts so much side pressure on footings that frost heaving can suck the footings up (and leave a holly below the footing). By going 10 feet I would have 4-5 feet below the frost which would stop this heaving due to side pressure. I went 12 feet.

_*10 feet below the frost line?*_ :surrender:

_dpach ..where are you located? ...please..just curious


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## dpach (May 12, 2009)

SteelToes said:


> _For example, books say to dig footings/piles to below the frost line. My local codes call for minimum 8 feet and strongly recommend 10 feet because I live in very gumbo type clay where frost puts so much side pressure on footings that frost heaving can suck the footings up (and leave a holly below the footing). By going 10 feet I would have 4-5 feet below the frost which would stop this heaving due to side pressure. I went 12 feet._
> 
> *10 feet below the frost line?*_ :surrender:_
> 
> dpach ..where are you located? ...please..just curious


 
Not 10 feet below frost line....10 feet deep footings because the frost line gets to 5-6 feet deep and they recommend a good 4 feet below the frost line here. I'm in Saskatchewan Canada. We get 5-6 feet of frost here in a lot of winters. 

There are people in the city here who have gone down 6 -7 feet with footings and still get heaving due to the sideways pressure the frost and gumbo soil puts on the footings. The heaving, combined with the pressure actually sucks the footings upward and it leaves a hollow void below the base of the footings. That's mainly due to our heavy clay gumbo soil that expands so much when wet and frozen. It cost me an extra $25/footing to go from 8 feet to 12 feet, so worth it to know they will never move.

I went 12 feet because that gets us into a solid base and since half of our city was originally backfilled 4-6 feet before building on it, it gets me about 6 feet into virgin soil. Plus, we have shallow oil here and though I might strike it rich! :laughing:

A lot of people forget to think about how their property was built. If it was backfilled 4-5 feet for proper grading before the house was built, digging piles/footings 6 feet down only gets you into 1-2 feet of virgin undisturbed soil for a solid base.


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