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First time builder, building a lifted deck.

Hello ^^;;

 

currently I am building an elevated deck which is not attached to the house in any way.

This deck platform measures 20'x20' at about 4' off the ground.

As of now I have nine 6"x6"x5' in the ground with concrete. These are square and sticking 3 feet out of the ground.

 

I wanted to use 4"x10" beams for the outside and center. (outside cut to 45 degree angles to fit)

I would then use 2"x10" beams for joists between and 2"x10" for blocking.

 

 

 

I was wondering and I have a few questions:

 

1) what kind of brackets would I use to fasten the frame of the platform to the base?

-1a) what braces should I use to hold the frame together? (hangers corners etc)

-1b) should I use bolts, screws or nails?

2) how exactly does the decking get put on top of the frame?

-2b) should I used 2"x8"s or shaved 2"x10"s so that the decking will be flush with the frame? Or does it go on top?

3) should I use five 4"x10"x20' or should I use ten 4"x10"x10'?

-3a) does it make a difference?

 

I will have more questions later. But thanks for looking at my post! :D

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Posted 2012-08-03T14:58:19+0000  by NerdrageIMO NerdrageIMO
 

Hello and thank you for joining our How to Community.

 

So this is your first time building a deck ha? You could have started with 10’x10’ or 12’x12’, it didn’t really have to be a deck and half for the first time … :smileyhappy: just kidding…I ‘m glad to help here as much as I can.

 

Let’s start from ground up… post and footings first.

So you’ve got a 6”x6”x5’ foot posts in ground with concrete, sticking about 3’ feet out of the ground.

That would make it about 2’ feet in ground right?

You haven’t specified your location but I’m assuming you’re in the warmer (nicer) part of the country where posts are not affected with freeze/thaw cycles? Otherwise your post footing would need to be placed bellow the frost line which is for determined by the location. For example here up north frost line is bellow 42” + inches.

 

Also depending on the location (soil type) and applicable local codes, post can or cannot be buried in ground. Some building codes require post to be placed on top of the concrete footing using a standoff type of base.

post-to-concrete.JPG

In the areas where in ground footing is allowed post that are used have to be rated for “in ground” applications. Treatment process used for these posts is different than from common pressure treated lumber. Normally on the stamp it will be indicated if post is rated for in ground application or not.

 

Enough about posts right:smileyhappy:

 

There are couple different construction methods that are used in deck construction. First is “beam flush with the joist”, with this method beams are at the same high as the joists.

Joist are connected to the beams using joist hangers that are nailed to the beams using galvanized nails and decking sits ,as always, on top of the joists.

jost hanger.JPG

This method is normally used with low platform type of decks where there is no room for standard construction or for the joists to be placed on "top of the beam" which is the second, most commonly used method.

 

With “joist on top of the beam” method joists sit on top of the beam that is perpendicular to the joists. In this case joists are connected to the beam(s) by using fasteners only or in some locations hurricane ties.

jost-to-beam.JPG

Last method is the one I should have probably listed first and that is a structure without the beams. This method is normally used on small decks where lumber can span its length providing for required loading per square foot.

 

In your case, considering height and size, you’re best of going with standard “joist on top of the beam method” with added diagonal al bracing.

bracing.JPG

Diagonal bracing are the supports that are installed diagonally in between posts and the platform of the deck. Purpose of the diagonal support is to prevent rocking of the structure that can occur with detached or free standing decks.

 

Going back to your material list…

 

You want to use 4’x10” beam lumber for the beam, correct? I’m assuming you’re referring to a three boards sandwiched together aka triple beam which would be 4.5”inches (3x1-1/2”)?Triple beam is probably an overkill ,normally double beam is sufficient.

 

Beam size is calculated using per square foot loading, exposure and span. Span calculators are readily available from manufacturers and in construction books.

 

One that I’m use to using is provided by the American wood council and its called AWC maximum span calculator

In this calculator you can enter the size and spice of the board you’re using, span, exposure and it will give you a maximum span that board can span.

 

For example @ 20’ feet a single yellow pine #2 and better 2x10 board @ 60psf of live and 20psf of dead load in outdoor conditions can span a maximum of 12’8” inches.

span calc.JPG

Live load and dead load requirements are going to be determined in your local “prospective deck handout” provided by your local building department.

 

Now your questions;

 

1) What kind of brackets would I use to fasten the frame of the platform to the base?

 

In your case beam should sit on top of the posts and connector that is normally used for this type of connection is pictured in image #3.

 

With “beam flush with the joist “method frame –platform is bolted to the posts using galvanized lag bolts.

 

1a) what braces should I use to hold the frame together? (hangers corners etc)

 

Joist hangers are used where joist are connecting to a support member, rim board (perimeter board) is not lead bearing and it does not need hangers. Corner braces are required for stair treads and stringers in some instances and a good practice for corners.

 

1b) should I use bolts, screws or nails?

 

Bolts for post to joist connections, to sandwich beams -staggered 24 O.C and for ledger to the house (lags).

Screws for decking and railing –need to be rated for exterior use. And nails (galvanized) or structural screws for joist hangers or similar connectors.

 

2) how exactly does the decking get put on top of the frame?

 

Decking sits on top of the whole frame assembly overhanging the frame for about ½” or so to divert water from the rim board. Boards should be installed with the annual ring facing down so that in case of cupping water doesn’t retain on top of it.

 correct.jpg

Also expansion and contraction gap needs to be maintained in between board butt joints.

 

 

-2b) should I used 2"x8"s or shaved 2"x10"s so that the decking will be flush with the frame? Or does it go on top?

 

Rim boards and joist should be same size. Decking sits on top of the both. You can use fascia ¾ board over the rim board to conceal fasteners.

 

3) should I use five 4"x10"x20' or should I use ten 4"x10"x10'?

Use span calculator to determine size and length of the beam.

 

-3a) does it make a difference?

 

I prefer long lumber and less butt joints.

 

Hope this helps,

 

George

Posted 2012-08-06T16:51:39+0000  by George_HD_CHI

what if i lived in the pacific northwest?

i live in tulalip washignton so we are hit with frosts at winter.

 

mostly wetlands out here.

 

am i gonna have to crane these posts out with the concrete and dig deeper?

Posted 2012-08-10T17:04:29+0000  by NerdrageIMO
the holes are 24" wide
Posted 2012-08-10T17:22:38+0000  by NerdrageIMO

I apologize but honestly I’m not familiar with building codes in your area. Your best resource would be your local building department.

 

If there is anything else myself or any of us on here can help you with, please feel free to ask.

 

George

Posted 2012-08-14T15:41:42+0000  by George_HD_CHI
 
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