# adding a deck to existing concrete porch



## idiotbox37 (Dec 1, 2009)

Hey guys,

this will be my first building project(i'm new to the forum!). I plan to do it this spring so i'm still in the early development phase.

At my house, the back door goes out to an existing concrete porch. the porch is about 3x3 and has two steps that go down to the back yard. I'd like to make a nice covered seating area where the porch is. My plan is to attach four 4x4 to the existing porch(using it as a base, basically) and then anchor two more 5 feet down the side of my house. I plan on framing it out and running floor boards all the way across from the far side of the concrete to the end posts (so the floor boards will be 8 feet long). I'll finish up by putting a slanted roof on it.

hopefully that makes sense and is easy to visualize. so, i have some questions. will i still need to anchor this to the house, since i'll have it anchored to the concrete porch? when anchoring the 4x4s to the porch, will ihave to worry about steal reinforcements in the concrete? what tool would i use to do this? i was thinking about anchoring into the side by using large screws but i'm not sure how to do that.

can you guys see anything wrong w/ my plans? Thanks!


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## Wildie (Jul 23, 2008)

Its best not to attach a deck to a house!
Its usually done as it is easier and cheaper to do!

How much room do you have above the concrete deck surface? Usually its about 7". If you use 4X4 joists and 5/4 decking, the deck surface would be about 3" below the door sill. Is this acceptable?
What would the size of the finished deck be?

You will need to research info about deck support spans etc. If you use 4X4 joists, you will need to know the distance apart for these and how they will be supported by the beams!


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## idiotbox37 (Dec 1, 2009)

i've attached a *rough* image of what i want it to look like.

the person is standing on the concrete porch. the door would be behind him.

I have estimated the porch as 3'x3' and the attached deck as 3'x5'. The support posts are 9 feet tall and 4x4.

the deck portion, being 5 feet long, will need two sets of joists. what is the recommended distance between posts?

I need to keep the height fairly low since my home is a one story and i need to watch out for the roof. my plan is to start the porch/deck roof underneath the house roof overhang, that way i don't have to worry about having a water tight seal between the house roof and porch roof.

is bolting those 4 support beams to the concrete porch a good idea? what kind of tool is needed for that?


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## Wildie (Jul 23, 2008)

idiotbox37 said:


> i've attached a *rough* image of what i want it to look like.
> 
> the person is standing on the concrete porch. the door would be behind him.
> 
> ...


 From your sketch it appears that you don't plan to cover over the concrete with the decking! yes/no?
Do you wish to attach the roof posts to the side of the existing porch?
Do you live in an area that is subject to snow load and frost heave?
In some jurisdictions any construction that attaches to the house requires a building permit. Have you considered this?


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## rocketdoctor (Mar 18, 2009)

I have just finished a deck that overhung a concrete pad. this is what I suggest considering your going to put planking over the concrete porch as well. 

Bolt a ledger to the concrete porch. Attach joists that go out to a beam thats attached to the 4X4s. put sleeps such as PT 2X4 bolted to the porch (is the slab sloped?). The top of the sleepers are flush with the top of the ledgers. Now you can run your decking along the hole way. 

Couple Notes:

Its frowned apon to bolt beams to the sides of 4x4 posts this was an accepted method in the past but not now. Latest decking rules suggest you always set beams ontop of posts so you might want to set your beam on posts seperate than the posts that support the overhang. If this is getting inspected check with the building plan office what is acceptable.

Use PT wood for all substructure. Since you don't have that much decking (sounds like 25 square feet) use some really nice hardwood such as IPE its a bit harder to work with and more expensive but beautiful (just my opinion though).

Really understand the whole entire project including any finishing touches you are planning adding so you can plan everthing exactly. When I do large projects I like to compile a list of things that I need and get lumber yard to deliver usually worth the delievery charge and not much more than a home depot or lowes.


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## rocketdoctor (Mar 18, 2009)

I forgot to include a really rough sketch I made for you below.

some additional info this is a good guide for construction and requirements you can see in section 8 how they don't want you to bolt to posts. http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf


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## tpolk (Nov 7, 2009)

if I understand correctly your shed roof is going under your soffit of the existing house. how are you finishing the roof under the soffit, making it water tight, keeping snow melt from wicking back into your soffit?


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