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Question DetailsAsked on 9/9/2014

What is the approximate cost of putting in about a 10' x 14' wood deck on the 2nd floor of a house?

We want to put a wood balcony/deck on the 2nd floor of the back of our house, replacing an existing large window with French doors to go out to the deck. There is an existing wood patio cover with posts down to a concrete patio below in this location. Can supports be added and a deck be built on top of this? It is bolted to the house, but not with sufficient beams to support a deck. We also would require HOA and City Building Permit approvals. We did get an estimate of $30,000 from one deck builder, but that price seems high to us. It is not a hilly location, though it is overlooking a mountain view. We were expecting around $10,000, so this came as a bit of a shock to us.

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4 Answers


Unlikely you can or should build on top of the existing patio cover - you will need a structural engineer to do plans for this job anyway so he can see if it can be incorporated, but unlikely economic to do so - though moving it up as a cover over the NEW deck might be a possibility. Also, if existing posts are not embedded in concrete or ground-contact treated timber, probably bestnot to reuse them for the new deck posts - go with new copper treated incised all-weather wood.

Depends of course on your local codes and planning and zoning regs and permit costs - but generally this type of deck would run about $30-50/SF all told for the engineering and deck plus from several to $5000 range for the french doors, ASSUMING the existing wall can carry the load without modification OR you also put support posts just in front of the wall to carry the house side of the deck load too - either works. For $10,000 range you would likely be able to get a pergola or awning over it as well - and your $10,000 number is quite realistic from my standpoint - I have done a lot bigger second story decks for $5000 range, PROVIDED they are not cantilevered.

One of the biggest cost drivers will be whether the existing rim joists can carry the deck (likely yes), or if the wall itself will have to be strengthened to carry the load. That is where the possibility of external support posts right in front of the wall will come in as a possible solution versus rebuildingthe rim joist area.

One thing to discuss with designer - EXCELLENT water control at the interface with the house, both with respect to setting the deck a bit low so rain or snow cannot get into the door frame, and with respect to getting the water away from the house and keeping it away with flashing, PLUS good waterproof backup at the rim joist in case any water gets behind the ledger board.

You will also have to look at what you want the front supports to look like - alongfront edge or with the deck cantilevered out some over the front support beam, and few or more legs - because the support posts will have to be embedded probably 3-6 feet into the ground depending on locale - they cannot sit on the patio for support, so either need to be set outside the patio perimeter, or holes cut through the pation and isolated from the posts so they can go down to concrete foundations in the ground.

Is it possible the builder thought you meant a cantilevered deck - that could run to $100/SF or more - but still rarely the $214/SF he gave you, which would in most parts of the country build an entirely new addition with that square footage with basement and roof and all - fully interior finished. Ditto to a high-end metal frame and glass enclosed sunroom cantilevered deck cost.

I would first do a check on building restrictions in your area (Planning and Zoning usually) and your property line clearances to see if likely doable. Then if so, get an architecture or engineering firm on board to help with permits and clearances and the design, then get at least 3 responsive bids from contractors for the construction.

Answered 5 years ago by LCD


One addition to my prior statement that came to me while working on a job today - before you run off thinking Oh Goody, we can do a cantilevered deck - a deck cantilevered out 10 feet without front support posts or angled-back supports from near the front edge back down to the foundation would be VERY unusual and pricey. Usually you can only go out about 4-6 feet out that way, and usually only viable if the deck is on a face of the house where the floor beams terminate at that wall - so you can put in new beams, parallel to and tied to the floor joists, effectively extending them outside the house. Otherwise, you normally have to have support posts like you were talking about, angle braces under the deck, or metal suspension rods or cables holding the deck up from a higher point on the house.

Just did not want you to get an idea a 10 foot free-cantilever deck is economically feasible - technically doable like the overlooks over the Grand Canyon and Niagara Falls and the overhanging decks on Frank Lloyd Wright's famous Falling Water house, but not generally economic for the average person.

Answered 5 years ago by LCD


This is a response to the answers above: This is for a deck that would NOT be cantilevered but built using concrete support posts. The $30,000 price included about $5000 for drawing up detailed plans and submitting to HOA and LA County and dealing with changes they might require. Then the other $25K is for removing existing patio cover and putting new posts to support the deck and then building the deck. Thanks for your input. We were not going to waste time getting other estimates since that is not even in the ballpark of what we hoped to spend on our deck. The French doors were not even included in that estimate. We were having someone else put in French doors and that would cost about $2700 which seems pretty reasonable I think.

Answered 5 years ago by Guest_934687538


Yes, $2700 for good quality (not cheapo box store ones) french doors, installed, is right in the range of a number of comments from contractors and window specialty companies posted recently on this forum.

Yeah - the $30,000 sounds WAY out of line - also, $5000 for the design is also WAY out - you can normally get a simple standard house plan (without specific artsy architectural features or inspection services) from an architect for about that. Should have been more like $500-1000 design for this structure - maybe $1500 with permitting included.

Also, unless you specifically want concrete posts, not the cheapest way to go and not generally the best material for your use - wood would be cheapest (normally 6x6 treated for 2nd floor balcony of your size), but structural steel H, square tubing, or round pipe section could also be used easily. There are also factory prefab structural porch/balcony posts that simulate classic column shapes like for colonial or plantation or old New England - commonly wood or concrete core with structural foam shape under fiberglass or similar resin outer finish, which can be retextured with stucco or painted as desired. However, if you want to skip any type of cross-bracing under the deck, then for a seismic area you would have to have one with moment-bearing column connections, which really narrows your choices.

Answered 5 years ago by LCD

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