[cg2000]

Hi, I'm working on a deck design. There are some wide spans, nearly 16' that I need to put a beam under partway across. Referring to the attached drawing the area south of the old retaining wall (brown dotted line) has about 3' of space under the deck and I can add a beam there no problem. However, north of the old retaining wall there is less clearance to grade and there isn't enough height to build a beam and rest the joists on it (its planned to be 8x2 PT Douglas Fir). How should I deal with this?

The way I have it drawn the beam north of the old retaining wall is effectively at the same level as the joists, and the joists are hung from either side of it. This would work structurally I think but might cause issues with drainage between deck boards that have a gap between them over the beam.

Any ideas or advice welcome.

 

[Nealtw]

Hi, I'm working on a deck design. There are some wide spans, nearly 16' that I need to put a beam under partway across. Referring to the attached drawing the area south of the old retaining wall (brown dotted line) has about 3' of space under the deck and I can add a beam there no problem. However, north of the old retaining wall there is less clearance to grade and there isn't enough height to build a beam and rest the joists on it (its planned to be 8x2 PT Douglas Fir). How should I deal with this?

The way I have it drawn the beam north of the old retaining wall is effectively at the same level as the joists, and the joists are hung from either side of it. This would work structurally I think but might cause issues with drainage between deck boards that have a gap between them over the beam.

Any ideas or advice welcome.

View attachment 586645

Number the retaining walls and how much higher or lower is each to the house floor what is the grey area to the right?

Where is the door from the house.

 

[cg2000]

OK, hope this makes sense:

Number | Relative Level Below Level 1 (inches) | Note

1 | 0 | floor level in the house (doors added)
2 | 1.5" | new retaining walls (deck will extend over walls edge of lawn**)
3 | 2.5" | Approx Lawn level, (just below that of the new retaining wall)
4 | 10" to 12" | Grade under Deck north of the old retaining wall
5 | 30" | Grade south of retaining wall

The intention is that the Deck is as close to the level of the house floor as possible (1), (likely 1/4" below it though) to give a flat transition out to the deck.

**the decking will stop about 1/4 short of the edge of the new retaining wall, and a 3/16th metal plate bolted to the wall on the lawn side, with its top edge flush with deck top surface, will form the lawn edge and protect ends of deck boards.

So the issue is that although above area 5 I have space for a deck beam under the joists, above area 4 I don't, so I'm trying to figure out how best to frame the area over area 4. I'm trying to avoid lowering 4 to accommodate a beam as there's existing drainage behind the old retaining wall that I'd rather leave alone, and would be hard to re-route.

 

[Clutchcargo]

Is a patio out of the question?

 

[cg2000]

Is a patio out of the question?

For now ... not a bad idea though ...

 

[Nealtw]

For now ... not a bad idea though ...

Will the door area be covered or protected from the weather. Level at the door way is a huge problem with leaks.

 

[Nealtw]

For now ... not a bad idea though ...

I have marked a 2x10 ledger all the way around in dark green Then you can leave a little space at the door with your first joist.

A double joist between 4 and 5 all joists with hangers, no need for center beam.

 

[cg2000]

I have marked a 2x10 ledger all the way around in dark green Then you can leave a little space at the door with your first joist.

A double joist between 4 and 5 all joists with hangers, no need for center beam.

Thanks, that's a solid design, a couple of issues though. There's not enough height in zone 4 to use 2x10 and have any clearance under the joists. I.e. some of them would be sitting on or very close to the ground which I understand isn't a great idea for the joists or the decking. Might this work with 2x8 at a closer spacing? 16" OC maybe?

Also, the double joist reproduces the same issue I had with my initial design in that there may be a drainage issue between the 2 deck boards that land over the double joist. (the deck will be 5/4 x 4")

 

[Nealtw]

Thanks, that's a solid design, a couple of issues though. There's not enough height in zone 4 to use 2x10 and have any clearance under the joists. I.e. some of them would be sitting on or very close to the ground which I understand isn't a great idea for the joists or the decking. Might this work with 2x8 at a closer spacing? 16" OC maybe?

Also, the double joist reproduces the same issue I had with my initial design in that there may be a drainage issue between the 2 deck boards that land over the double joist. (the deck will be 5/4 x 4")

I would not put 5/4 decking on less than 16" OC.

16 ft is pushing your luck with 2x10s
I have never built that wide with 2x8s. actually we seldom built anything with 2x8s so getting opinions from others may help.

I would be thinking double 2x8s for that long span.

And there is a cheat for drainage. and you will be covering the top of all joists for drainage too.

 

[cg2000]

Ah, nice! That drainage trick actually may solve the whole problem with either design. Given that it's 2x8 I'd rather put the support mid-span and use this trick to help with drainage.

Only other idea I've had is to notch the end of each joist (cut a 6.5" x 0.75" piece out of the end) where it hits the beam so that an inch or so of it sits above the beam. I would still use hangers to take the load, but only the joists would be touching the boards.

 

[Nealtw]

Ah, nice! That drainage trick actually may solve the whole problem with either design. Given that it's 2x8 I'd rather put the support mid-span and use this trick to help with drainage.

Only other idea I've had is to notch the end of each joist (cut a 6.5" x 0.75" piece out of the end) where it hits the beam so that an inch or so of it sits above the beam. I would still use hangers to take the load, but only the joists would be touching the boards.

The siding should be removed for a proper installation. Post a picture of what you have so we can talk about it.

 

[udraft]

I believe steel is a bit stronger by depth.

 

[cg2000]

The siding should be removed for a proper installation. Post a picture of what you have so we can talk about it.

Will do tonight.

What do you advise as to the best way to hang the joists from the header joists where they meet at an angle? Standard Joist hangers won't work

 

[Nealtw]

Will do tonight.

What do you advise as to the best way to hang the joists from the header joists where they meet at an angle? Standard Joist hangers won't work

They make angled hangers at 45 degrees. They come in right and left if that is confusing just buy both and return what you don't use.

 

[cg2000]

Got it. The angles I'm dealing with are more like 30 degrees and 60 degrees, I don't think these will work too well. Is there a hanger part that can be bent to any angle? Or some other method all together that's acceptable? Or I guess I could just tweak that part a little.

 

[Nealtw]

Got it. The angles I'm dealing with are more like 30 degrees and 60 degrees, I don't think these will work too well. Is there a hanger part that can be bent to any angle? Or some other method all together that's acceptable? Or I guess I could just tweak that part a little.

Yes before we had hangers they used pressure blocks. Inspectors don't like them because they can't see all the required nails.

Your beam will be 2 ply, but you hang the joist when you just have one piece of the beam up.

In the first picture you can see nails thru that beam piece and nails on angle and the joists 3 nails in each position.

Then you add the other beam part with 3 nails every 16"

then you cut blocks that I show in green and again nail the crap out of that.

If you count the nails on a hanger you are doing much more than a hanger would do.

Hopefully this is clear enough.

 

[cg2000]

Ah, ok, yes I think I get it, thank you for the info and the illustration

 

[cg2000]

Here are some images of the site:

https://www.dropbox.com/sh/sxhqvxl8v7m1b0x/AABzIP2f1YUKloyp2yNalujea?dl=0

 

[Nealtw]

Here are some images of the site:

https://www.dropbox.com/sh/sxhqvxl8v7m1b0x/AABzIP2f1YUKloyp2yNalujea?dl=0

I see a couple problems we have not discussed.

 

[Nealtw]

Also, the double joist reproduces the same issue I had with my initial design in that there may be a drainage issue between the 2 deck boards that land over the double joist. (the deck will be 5/4 x 4")

There are a couple ways to deal with this we can talk about.