Front porch design

[dug]

I need a little help with the design for the front porch I am building on the home below-



I will do my best to describe what I have going in the fewest words I can, so hang with me please!

I am planning to put in 5 concrete piers about 6 or 7 in. above grade, 8 ft. out, perpendicular to the existing ones on the front of the house. Piers are on 7 ft. 3 in. centers. Connected to these would be 4 by 8 posts running up to support a rafter header beam (?). Resting on the piers that support the house, and connecting to the upright porch posts, would be 4 by 10 beams that will carry the deck joists. Joists will run parallel to the house, on 24 in. centers. They will be 2 by 10's, which I think is overkill but they will bring the deck to the correct height.

While staking everything out I discovered that this design would place a post directly in front of both windows and the door!     So now I would like the posts on 10 ft. centers.

I was hoping I could use the same basic design to build the deck and somehow attach posts on 10 ft. centers on top of the deck. Is this O.K.?

(2) What sort of lumber would I need for the rafter support beam on 10 ft. centers? It will be a relatively light roof. Purlins, metal, very low snow load area. 2 by 6's or 8's for the rafters.

(3) Am I missing an obvious, better way to do this?

Thanks much!

[John Raabe]

Let me see if I have the picture of what you want to do.

• The house is 30' long and you want to add a full length shed roofed porch that is 8' deep.
• You want to support the porch with 4 posts spaced 10' o/c

If that is right, here is the next question:

• Are you building from one of my plans? (Much easier to explain how to modify the porch layout you already have.)

[dug]

Yes. Porch will be 30 ft. by 8 ft.

Also correct that I want 4 posts on 10 ft centers.

I am working off your plans for 20 by 30 1 & 1/2 story, though I have made slight modifications here and there.

[John Raabe]

Great. See the porch and deck plan and details on sheet 8 (the little page number in the lower right-hand circle - the big page number in the title block is 6). Note how the deck beam is notched into the 6x6 posts and the posts go up and support the roof beams. Note that the beams, deck joists and roof joists are all designed for a max span of 10' between the posts. This is for light snow country, which it sounds like is your situation.

I think your all set. It makes a nice porch. I built mine the same way.

[John_M]

I know this has been said before and I know some people are set in their ways....but the number one regret I have with my cabin is NOT having a 10 foot porch instead of an 8 foot one.  It doesn't cost that much more and the amount of room you gain is really beneficial.   Just something to consider!

[OkieJohn2]

Have you considered not having the posts on even centers?  What I mean is having the two center posts closer together, to flank the entry door and supporting hand rails for a wide stair leading down to ground level. This might require going with 6 piers, two to only support the floor and a hand rail support, not going all the way up to the roof.

[dug]

Insert Quote
Great. See the porch and deck plan and details on sheet 8

I get it, I actually have to read the plans eh? Not woe of my stronger points. 

Seriously though, I did go through it but I don't think it will work because of a design change I made. For reasons that don't seem so important now I placed the piers a few inches inboard from the beams. See photo below-




This leaves the rim joist hanging over the edge and I wouldn't think that would be a good place to attach the deck joists to. Is that correct?

This is the reason I was thinking of running the support beams perpendicular to the house, like this-



these beams would attach at the posts, into a 1 @ 1/2 in. notch, and joists would be on top running parallel with the house. Deck beams would run perpendicular to house, which I like better. But then I'm back to the problem of trying to get the posts @ 10 ft, centers.

[dug]

Oop's, didn't quite finish the last post- posted when I was trying to preview. 

I hope at least some of this makes sense and am very interested to hear your opinions, especially from John in regards to using the standard plan with my foundation modifications.

As to the 10 ft. porch-

I know this has been said before and I know some people are set in their ways....but the number one regret I have with my cabin is NOT having a 10 foot porch instead of an 8 foot one.  It doesn't cost that much more and the amount of room you gain is really beneficial.   Just something to consider!

A 10 ft. porch would be nice but I am trying to keep it as high as possible, so as not to restrict the view, and I'm fighting for every inch. 2 ft. farther out would lower it another 6 inches.

[John Raabe]

I think I understand better what you are trying to do... If you extend beams perpendicular as you show in the mock-up photo they want to land on a pier as well since they are carrying and aggregating the floor load from the joists.

You could still layout the posts the way you want (10' o/c) and have the outside porch beam oversized to take the load from the intermediate perpendicular beams. That is a more complex loading to analyze since you now have point loads landing at different points on the beam. A 6x12 would probably be oversized but it would be a quick engineering problem to size it more accurately.

The decking will be running the depth of the porch rather than the length. Maybe that isn't an issue but it seems slightly unnatural to me.

The other way to do this is to just block out a 2x8 ledger with bolts back into the floor system say every 4'. (I suggest two 5/8" thru bolts w/ washers.) Then you could build the deck and porch roof the way it is shown in the plans.

[dug]

Thank you John. That gives me something to think about.

I actually like the idea of the decking running the depth of the porch. I will see what I can come up with.

[dug]

One more question I have-

I am not sure what I will use for the decking yet but was hoping I could use regular (non-PT) lumber for the beams and joists. Is this O.K.? One of the beams would be about a foot from the ground.

Thanks.

[John Raabe]

While using PT or cedar for joists and decking will last longer, you are not required to have PT material unless the wood is closer than 8" from soil.

[rwanders]

What pitch do you plan for the porch roof? If you could flatten it out enough to allow for a 10' depth , I believe you will be very happy with the result----the extra 2' really makes a remarkable difference in the look and feel of a porch. An 8' porch that is also 30' long may appear pretty long and skinny.

[dug]

rwanders- I have staked out and run string lines for the 8 by 30 porch and you are correct, it does appear a bit skinny. However, I already have the materials and money is running a bit tight so 8 ft. it is. In retrospect I probably should have went with 10 ft. deep.

Roof pitch will be 2 & 1/2/ 12, which should place the bottom of the beam that supports the rafters at a little under 8 ft. above the deck.