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grover
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# Posted: 24 Jun 2015 10:57pm
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I have a porch that runs the full length of the cabin front. It has 6 x 6 posts 8 ft away from the cabin holding up the roof of the porch. I want to build a deck under this and have attached a ledger board to the cabin but I'm not sure how to attach the outside beam opposite the ledger board. My first thought was to notch the outside of the posts and bolt my outside beam to the posts. This would mean having each end of the board that makes up the outside beam to meet at the midpoint of each post. Only 2.75 inches of each beam resting on the notch. For some reason this does not seem solid to me. Maybe it is the way it should be done but I'm not sure.
How would you attach the outside beam? Should it be double thickness beam, (3 inches) and be attached to the inside of the porch posts? Help!
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bldginsp
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# Posted: 25 Jun 2015 08:25am
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It would help if you could give us a drawing.
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grover
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# Posted: 25 Jun 2015 11:46am
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Not sure how to load a drawing on here.
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beachman
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# Posted: 25 Jun 2015 01:13pm
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I suppose it depends on the length between the posts on the outside but I would at least double the beam opposite the ledger board. I would run joist hangers for each 8ft joist and use 8inch joists for strength on 16inch centers. I would probably not notch the posts as I wouldn't want to impair the integrity of the posts with an over cut, but I would probably put supports - either 2x4 pieces or steel brackets under the beam as well as bolting them to the posts. This is total non-scientific and certainly not code calculated - just my opinion.
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grover
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# Posted: 25 Jun 2015 02:25pm
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See if this works.
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bldginsp
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# Posted: 25 Jun 2015 02:37pm - Edited by: bldginsp
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Now I see what you are doing, and yes, attaching the ends of the beams with only 1/2 purchase on the posts in the middle is not good. Best thing would be a full length beam. Another solution is to put the beams inside the posts and use butt end hangers. Or, put the beams inside the posts and bolt supports to the posts under the ends of the beams. Beams need solid support and connection.
If you use three separate beams in any configuration, strap them at the joints to keep them from coming apart.
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grover
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# Posted: 25 Jun 2015 03:24pm
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Not sure I like the idea of hangers for the beam on the inside of the posts. Might work fine, just sounds strange.
2 x 10's are what I have on hand for the ledger, beam, and joists. When you say a full length beam, do you mean nailing multiple 2x10's together creating a beam that is roughly 3 inches thick x 28 feet long?
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bldginsp
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# Posted: 25 Jun 2015 05:32pm
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Not what I meant but it's possible. I meant getting a 28 foot beam, special order. I wouldn't nail together 2x lumber for an exterior situation cause water will get in between and rot.
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Don_P
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# Posted: 25 Jun 2015 06:28pm
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No joy on the pdf here.
Nail together multiple plies to create a built up beam if you go that route... use pressure treated lumber, the decking will fail long before the beam rots if you use .40 or better treated. It is stronger and better treated than a custom thick timber and a fraction of the cost.
There is nothing wrong with beams inside the posts, use the hangers with inturned ears, Simpson HUC or similar.
Deck design, beam and joist spans etc are in a publication called DCA6 on the awc.org website
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morock
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# Posted: 25 Jun 2015 09:34pm
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I would use a 2x material on both the inside and outside of the posts, attached with treaded rod. Add some blocking in between the posts as needed. Then cantalever the floor joist over this beam. I assume you have some roof over hang past the posts? Take advantage of all the roof you have.
I prefer the joist over beam vs hangers, but that just my $0.02 cdn.
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toyota_mdt_tech
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# Posted: 25 Jun 2015 09:36pm
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I was wondering why the beam would need to be on the outside. Could one beam be on the inside of the post, no notching (I would not notch those post for any reason) and add a cleat or sister another board onto the original post (treated) right down to the footing and that would carry the deck load, no deck load would be placed on the post iself and the deck would square tighten it up besides.
Could you run the decking planks 90' from original design (not parallel to deck, but away from it), this way, you can run the decking past that support beam running your deck to the outside edge of the post (slightly cantilevered) decking to make it flush as I assume you will put railing between support post. This would eliminate the "hole" under the railing. Other end would tie into the ledger on the cabin and the joist betwee them. You would have to use probably a girder for the longer decking joist (middle area) as the span would be longer. Just another option. 
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morock
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# Posted: 25 Jun 2015 10:06pm
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I would use a 2x material on both the inside and outside of the posts, attached with treaded rod. Add some blocking in between the posts as needed. Then cantalever the floor joist over this beam. I assume you have some roof over hang past the posts? Take advantage of all the roof you have.
I prefer the joist over beam vs hangers, but that just my $0.02 cdn.
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morock
Member
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# Posted: 25 Jun 2015 10:18pm
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Not sure how the posting was duplicated. I usually say things twice anyway.
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grover
Member
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# Posted: 25 Jun 2015 11:15pm
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If I do a 2x on the inside and another on the outside of the posts I'm still left with the situation of needing to splice the 2x's somewhere. That would have to be at each post unless I come up with a 28 ft 2 x 10.
The hangers inside the posts sounds like the easiest solution by far.
The other possibility is the double 2x nailed together to create a 28 ft beam. I then would get a 4 x 6 treated post cut in short sections to bolt to the posts below the beam to help support the beam. I didn't like the idea of notching the posts either but I know it needs to be supported by something other than bolts. The deck will only be about 2 ft off the ground.
I'll check the awc.org website tomorrow.
Thanks everyone.
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Don_P
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# Posted: 26 Jun 2015 07:22am
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Correct, never hang a floor from just bolts or rods through the beam. The injunears show us picture after picture of split beams generating from the bolt holes, often just from drying and shrinkage of the beams. Another rule of thumb; when bolting things up is never space bolts wider than 5" across the width of a timber, the high and low bolt pattern in the end of a 2x10 or 2x12 often causes a split in between the bolts.
If you run the joists 90* to the house there will be a beam from each post back to the house with joists running parallel to the house. At each girder to house connection I usually run a 6x6 from the house footing up to the underside of those girders... a ledger there with code bolting is not up the task of supporting the concentrated load of a girder. The inboard house connection is normally where decks collapse.
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bldginsp
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# Posted: 26 Jun 2015 07:42am - Edited by: bldginsp
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Quoting: Don_P If you run the joists 90* to the house there will be a beam from each post back to the house with joists running parallel to the house.
Excuse me, I used to be an editor:
'If you run the GIRDERS 90* to the house....'
I think this is a good solution, but there has to be a way to connect the girders to the house. In this case the entire attachment of deck to house is with 4 girders, if the joists are perpendicular you have 20 joist hanger connections. I'd try to strap the girders to house joists or blocks between the house joists to get them tied to the floor diaphragm.
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grover
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# Posted: 26 Jun 2015 09:50am - Edited by: grover
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The plan was to run the floor joists at a 90 degree angle to the ledger board with hangers on the ledger and beam for each joist. That will make my deck boards run parallel to the house. Running the floor joists parallel to the ledger board creates a lot more complexity with beams at every post. If I was unsure of my ledger board connection I could bury several 6 x 6 posts about a foot from the house and run another beam parallel to the house for my joists to rest on. If I was going to do that I wouldn't have even had a ledger board and done it free standing.
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Don_P
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# Posted: 27 Jun 2015 10:01am
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Quoting: bldginsp 'If you run the GIRDERS 90* to the house....'
Yup, Thanks
Quoting: grover The plan was to run the floor joists at a 90 degree angle to the ledger board with hangers on the ledger and beam for each joist. That will make my deck boards run parallel to the house
This is prescriptive if the house is on a prescriptive foundation, the ledger connection is outlined in the code and in DCA6. It's a good way to go. If the rim joist is part of a cantilevered floor system read that section of DCA6.
............................
Backing up to just generally talk about this a little more;
Quoting: bldginsp 'If you run the GIRDERS 90* to the house....' I think this is a good solution, but there has to be a way to connect the girders to the house. In this case the entire attachment of deck to house is with 4 girders, if the joists are perpendicular you have 20 joist hanger connections. I'd try to strap the girders to house joists or blocks between the house joists to get them tied to the floor diaphragm.
bldginsp is talking about the lateral connection to the house, the deck pulling away in a horizontal direction. Although for years we have effectively been using those joist hangers to restrain that force, they are not tested or rated for that load direction. In the previous 2 code cycles they have been calling for a 1500 lb lateral connection near each end of a deck from the deck joist, through ledger and rim, to a house joist. They have, I believe, dropped that requirement in the latest version but do keep the intent in mind. This is bldginsp's very valid concern when there are just a few girder connections between house and deck to form that path of horizontal load resistance.
This is the reason I put the house side 6x6 against the foundation wall, sitting on and clipped to the house footing (why place a spot footing 1' away from a continuous footing). The post is bolted to the wall or (usually) the rim and supports the ledger and girder. Although the ledger at the house is not carrying joists it is still code attached to help resist the lateral load through the deck floor. In other words I build it freestanding for vertical load (posts under the ledger and girders) and attach it to the house to resist horizontal load.
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grover
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# Posted: 5 Jul 2015 07:50am
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I got the beam and the joists installed yesterday. I put 1, 2 x 10 between the posts with hangers. The other 2 x 10 is nailed to the out side of that beam along the length and then bolted to the outside of the posts. Next trip I will bolt 2 x 6's vertically on the outside of the posts under the horizontal beam for support. Now I'm going to do some searching for screws to attach the deck boards. I'm looking into the hidden type but I may just use the good old fashion deck screws. Thanks
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grover
Member
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# Posted: 5 Jul 2015 10:13am
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Sounds like the hidden fasteners are only recommended for the composite deck boards. Real wood may warp and cup too much for the hidden ones.
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Don_P
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# Posted: 5 Jul 2015 04:08pm
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There are concealed fasteners for solid wood although I've never used any of them.
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