New deck w/ screened porch & roof

Henry W

HenryW
Senior User
That is a confusing statement that seems unrelated to a deck. Can you explain please?
I would GUESS that he means that: Minimum codes make for a deck that is 'bouncy' rather than the 'rock-solid' feel of a deck where the framing is selected at greater than their minimum allowable size.
 

Saal

Gene
User
I have been getting quotes/estimates on tearing off the deck on my house and replacing with a screen porch and roof. The joists are starting to show deterioration and I can't see putting walls and roof on a so-so framing structure. The deck is also not level....several inche of drop from house to outer side. Not sure if it was built that way or it got that way over time. I don't like the way the faux trex looks (not sure how long it's been there) so will replace it also. The house is 50 years old and I don't know if the support structure is original or not.

Out of 5 estimates, only one has proposed using more posts than the current 3 posts and it was the lowest estimate....about half what the bigger companies want. The current and new structure will be 12' x 20' with the 12' sides going away from the house wall. I just don't see the need for 2 new posts 6' from the house wall and two more at the house wall. I've seen screen porches this big and bigger with just the outer support. Tell me I'm not crazy. Here is a pic of the current deck. I believe they would all use 2x12's for the ledger board and double rim joints with 2x10 floor joists. Yes, I know, the dish will have to be moved...lol.

View attachment 195822
 

Saal

Gene
User
I have been getting quotes/estimates on tearing off the deck on my house and replacing with a screen porch and roof. The joists are starting to show deterioration and I can't see putting walls and roof on a so-so framing structure. The deck is also not level....several inche of drop from house to outer side. Not sure if it was built that way or it got that way over time. I don't like the way the faux trex looks (not sure how long it's been there) so will replace it also. The house is 50 years old and I don't know if the support structure is original or not.

Out of 5 estimates, only one has proposed using more posts than the current 3 posts and it was the lowest estimate....about half what the bigger companies want. The current and new structure will be 12' x 20' with the 12' sides going away from the house wall. I just don't see the need for 2 new posts 6' from the house wall and two more at the house wall. I've seen screen porches this big and bigger with just the outer support. Tell me I'm not crazy. Here is a pic of the current deck. I believe they would all use 2x12's for the ledger board and double rim joints with 2x10 floor joists. Yes, I know, the dish will have to be moved...lol.

View attachment 195822
Wh
 

Wolfpacker

Brent
Senior User
2x8 12 foot floor joists on 16 inch centers can support 40 lbs live plus 10 lbs dead load. Live load is you, dead load is the roof and furniture. 2x10s look like overkill. If you use wood flooring, 16 inch centers works but trex usually needs 12 inch - which would make the 2x8s overkill.

How many posts you need is a function of how large the beam and posts are. I did not consult the tables for a doubled 2x12 but it is not hard to do. Whether posts are required at the house side is dependant on what the house can support. That could get a bit involved if there are windows and doorways. The addition of posts may be a way to avoid tearing into the walls to see what is there. My guess is that you don't need them unless you have wide windows or doorways in that wall. Something like a sliding glass door under the ledger means the ledger has to be another good sized beam and there need to be at least doubled and possibly tripled 2x4s holding it up. Or you have to at least partially support the porch with posts. I don't intend this to be an answer, just some ideas on considerations.

I turned a porch into a screened in porch over 10 years ago and I did not have posts at the house. The wall under the ledger had only one small window. It was fine. The side away from the house had a doubled 2x12 beam which rested on 4 brick columns. The porch was about the same size as yours, 12 feet wide and at least 20 feet long, might have been 24 feet long. I put a shed roof over it which is easier to frame and tie into the existing house. Personally I would not worry about the existing soffits and facia until the porch is framed up. But with a contractor I understand the need to get things written down up-front. I think the key thing is how the ceiling of the porch looks - how much comes off should be whatever it takes to make the porch ceiling look whatever is "right" to you. I put vinyl soffit material on the underside of the roof rafters so it had a cathedral ceiling. I don't think I took the old soffit and facia off.
There is a sliding glass door under the ledger board. The house is brick veneer. Looking from inside the unfinished basement, there is a concrete block wall up to the rim joist and the ledger board is bolted to the rim joist. I plan to have a gable roof with a vaulted ceiling with T&G on it. I want the existing soffit over the deck removed so that it looks like the porch could have been original to the house.
 

Wolfpacker

Brent
Senior User
Although less than ideal, it's not a huge deal to move a drain line. Pool installers do this all the time, so you just need to find a septic installer that can manage the re-location and approvals.

Cantilevering 29" for 2x12 @ 16"OC is within the code (NC Residential Code, Table R502.3.3(1) via Appendix M 106.2). You can go farther with design by a licensed structural engineer. So your post could be 36" behind your current edge of slab with the extent of the new deck face just 6" behind your current without having to move the drain line.
Thanks Steve. I don't have much real estate to move a line. If the septic locator guy is right, this 50 yr old system only has one line/trench. It works tho. Going from the drain field away from the house is a fairly steep slope followed by a more gentle slope for about 30 ft, then woods. It is on the side of a mountain so to speak. Someone I spoke with suggested putting in solid pipe for 20-25 ft where the footers would be and adding drain pipe back somewhere else. That may be a possibility.
 

SteveHall

Steve
Corporate Member
Thanks Steve. I don't have much real estate to move a line. If the septic locator guy is right, this 50 yr old system only has one line/trench. It works tho. Going from the drain field away from the house is a fairly steep slope followed by a more gentle slope for about 30 ft, then woods. It is on the side of a mountain so to speak. Someone I spoke with suggested putting in solid pipe for 20-25 ft where the footers would be and adding drain pipe back somewhere else. That may be a possibility.
Good info. Sounds like it may be more fragile than I realized. You'd probably be smart not to alter your current septic system unless you really want to risk re-doing the whole thing. Your county might be easier to work with, but here in the Triangle, re-permitting alterations on old septic systems can be a huge pain, especially if they want to re-evaluate the soils and/or system design itself. You might end up having to re-test percolation, replace/enlarge the tank, add more line capacity/size/length, add a pump, or even clear some new flood zone buffer or well that wasn't there when originally constructed. These may even make it infeasible/impossible. Some of my residential projects are severely limited in scale (bedrooms) due to septic system limitations. (For example, 4 bedrooms max on one 13 acres site here in Wake County.)

It's probably better just to engineer the new deck around it. You should anyway with a roof since it adds more loads. My recommendation would be to make the whole thing free-standing and not structurally tie in to the house except to connect the roof. That gives you the opportunity for more cantilever length since the opposite side posts can help, too.
 

RobH

Rob
User
I suspect the posts 6’ from the house have to do with the weight load of the roofed structure. Could probably get a round that with heftier joists. One reason to do that would be to help control the bounce of the structure with 12’ long joists only supported on the end. Also, there might be load concerns about your ledger attaching to brick veneer. I did a DIY screened porch a few years back and had code approved plans for ledger on house (no brick) Support beam 7’ out under the joists, and the end beam 14’ from house. The beam in the middle made a huge difference in bounce from the deck it replaced. Here is a link to a different forum where I posted the build so you can see what I’m talking about. Screened porch project
A structural engineer might be worth the $ to design the supports and roof.
 

Grimmy2016

Board of Directors, Development Director
Scott
Staff member
Corporate Member
I'm having the contractor put down screen over the joists before putting down the floor.

If you end up leaving the sites open to the weather, even with screens, I might suggest using EDPM under the deck. I JUST did this last week with my new deck and it makes the space underneath usable as well as it keeps rain and leaves from falling through.

Withyou wanting to cover the new porch/deck it may not be as necessary, but it would helpkeep critters coming up and reduce any wind from below. Just my two cents.
 

Wolfpacker

Brent
Senior User
I suspect the posts 6’ from the house have to do with the weight load of the roofed structure. Could probably get a round that with heftier joists. One reason to do that would be to help control the bounce of the structure with 12’ long joists only supported on the end. Also, there might be load concerns about your ledger attaching to brick veneer. I did a DIY screened porch a few years back and had code approved plans for ledger on house (no brick) Support beam 7’ out under the joists, and the end beam 14’ from house. The beam in the middle made a huge difference in bounce from the deck it replaced. Here is a link to a different forum where I posted the build so you can see what I’m talking about. Screened porch project
A structural engineer might be worth the $ to design the supports and roof.
Nice job on your porch and deck. I like the lighting...low voltage or 120V ? I have had an engineeer spec the joists, girders, rafters, etc. and now have contractors saying "you can't do that by code".. Geeshh ! This would be simple if it weren't for the drain field requiring a cantilever design....sigh.
 

RobH

Rob
User
Nice job on your porch and deck. I like the lighting...low voltage or 120V ? I have had an engineeer spec the joists, girders, rafters, etc. and now have contractors saying "you can't do that by code".. Geeshh ! This would be simple if it weren't for the drain field requiring a cantilever design....sigh.
Thank you! The porch lights are all low voltage. There is a transformer under neath the porch. Concealed the wires in the wood structure. Happy to send a diagram of how I hid the wires if/when you get to that point.
 

SteveHall

Steve
Corporate Member
I have had an engineeer spec the joists, girders, rafters, etc. and now have contractors saying "you can't do that by code"
This sounds backwards. There shouldn't be any licensed engineer designing anything not to code.

But there are multiple methods of meeting code. Usually "to code" on a jobsite means the actual prescriptive methods specifically spelled out in the residential code for light wood framing. For commercial projects, there are too many types of buildings and construction type so there's not much prescriptive. So they rely on the expertise of the engineer. (Think skyscrapers, stadiums, nuke plants, bridges, etc.) Performance design is also permitted by the residential code, and is common for complex or large residential projects. Frankly, I find this always superior to the prescriptive code anyway because you have an engineer quantifying actual loads and conditions, not just hypothetical assumptions from the prescriptive method. There are many troublesome conditions prescriptions don't consider very well, but other times they are overkill.
 

Jeff

Jeff
Corporate Member
This sounds backwards. There shouldn't be any licensed engineer designing anything not to code.

But there are multiple methods of meeting code. Usually "to code" on a jobsite means the actual prescriptive methods specifically spelled out in the residential code for light wood framing. For commercial projects, there are too many types of buildings and construction type so there's not much prescriptive. So they rely on the expertise of the engineer. (Think skyscrapers, stadiums, nuke plants, bridges, etc.) Performance design is also permitted by the residential code, and is common for complex or large residential projects. Frankly, I find this always superior to the prescriptive code anyway because you have an engineer quantifying actual loads and conditions, not just hypothetical assumptions from the prescriptive method. There are many troublesome conditions prescriptions don't consider very well, but other times they are overkill.
Can you just tell the OP what he should do without all of the other jargon? Specifically what he should copy from where and show his contractor. No doubt that you're well qualified for this advice.

 

Wolfpacker

Brent
Senior User
Thank you! The porch lights are all low voltage. There is a transformer under neath the porch. Concealed the wires in the wood structure. Happy to send a diagram of how I hid the wires if/when you get to that point.
Please send diagram...if I wait until that time, I'll forget where I saw it ! Thanks !!
 

Wolfpacker

Brent
Senior User
This sounds backwards. There shouldn't be any licensed engineer designing anything not to code.

But there are multiple methods of meeting code. Usually "to code" on a jobsite means the actual prescriptive methods specifically spelled out in the residential code for light wood framing. For commercial projects, there are too many types of buildings and construction type so there's not much prescriptive. So they rely on the expertise of the engineer. (Think skyscrapers, stadiums, nuke plants, bridges, etc.) Performance design is also permitted by the residential code, and is common for complex or large residential projects. Frankly, I find this always superior to the prescriptive code anyway because you have an engineer quantifying actual loads and conditions, not just hypothetical assumptions from the prescriptive method. There are many troublesome conditions prescriptions don't consider very well, but other times they are overkill.
He's not designing anything that's not to code in my opinion, Contractor is misinterpreting the code.
 

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