Do I need an engineer for concrete patio
A HO wants a concrete patio of stamped concrete. The house is two levels, the bottom level at the back of the house where the patio is to be built is the entrance to the basement level of the house. The entire backside of first level of the house is at ground level (BT won’t let me attach pics for some reason). Level 2 of the house is entirely at ground level on the front of the house. In other words, the ground level elevations are at differing heights, the front being higher than the back.
As such in order to put a patio on the backside of the house as the HO wants the patio will have to have a full sized basement of its own. The basement ceiling will in fact be the patio above for the second level.
I plan to build the walls to support this patio out of block. It will rise about 10 or 11 feet from ground level to meet the second level of the house. The overall size of the patio is to be 18×45.
Now, having never done this before, how does one determine the size and spacing of steel beams upon which to lay corrugated decking to pour the concrete on to form the patio? I”m assuming the patio slab should be 4″ thick concrete? Well what kind of steel? Direction of beams, size of beams, etc? Is there a good rule of thumb, or is this definitely engineer type work? If engineer type work I assume an architect?
Replies
in short...get an engineer.
Sounds to me like you definately need an engineer. BTW - IMO, an engineer helps you know how to build something. An architects place is to help you decide what to build but is supposed to also know how to build it. Personally, I'd get a PE - Professional Engineer. I'd wing it on a 6'x10' porch and such but you are talking about quite a good sized structure - 18' x 48'.
Yeah, 18x45 is pretty huge IMHO. I think I need an engineer, but I'm doing an estimate, I dont' want to spend funds on an engineer and not get the job only to be out of money. Know what I mean? So though it's dumb to ask as I have, I thought I'd ask anyways just in case there is a rule out there that helps.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I think this calls for a design or engineering only contract. Knowing up front that the only way this project can be accurately estimated is to have a PE's stamped plans, the customer, if they really want their project, will agree to pay for the plans. These plans will belong to the customer and then it would be up to you to complete your proposal and sell the job.
Also, if you are not being paid for your estimates, then the entire transaction with the engineering firm should be between them and the customer. The customer can then distribute the data to you and/or your competitors. Don't knock yourself out unless the customer has committed.
You need an engineer.
As you have no experience, I'd also suggest an engineer. Don't forget to ask about bar joists, which will make your life a lot easier than beams.
After building something similar here (that we live in) our building dept now only asks for the bar joist chart to check my selection. But I already have my engineering for the walls and attachments. It's really a pretty simple process. Next house has what you describe, but the bottom level's an indoor pool.
PAHS Designer/Builder- Bury it!
Indoor pool in the lower level? I love it, seeing as the HO has lots of money, maybe I outta suggest that :)If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I have to go with what Ralph said. Tell the customer this needs some engineered plans and that is going to cost X amount. Go down and talk to an engineer tell them what your up against and ask for a rough estimate on his/her time. You could then give the customer an estimate with the $500 or whatever fee in there, but it seems to me if you have never done this before it is going to be hard to get an accurate estimate without looking at some kind of design.
Jeff
And depending on how you do the pool, it doesn't have to be "lots of money". This'll be my first. Have several requests for discussion, following my completion. Tickles me immensely that I've apparently figured out how to beat the normally very high cost of a pool here.
BTW, you mentioned block walls? Why cmu?PAHS Designer/Builder- Bury it!
Ok, I'm dumb, what is cmu?If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Not dumb. Sorry, concrete masonry unit. Not something I would consider using.
As Bill points out, you could use ICF (I don't). But either way, cast-in-place is pretty simple and immensely stronger. And your engineer will strongly approve.
Here's my first attempt. 30' span and design load (total) of 300 psf, which is considerably more than you'll be dealing with. Meaning, if you use bar joists, they'll be considerably smaller and fewer. I welded the decking down, but have progressed to shooting it down with powder actuated. Slab on top was nominally 4". Makes for a very inexpensive building. PAHS Designer/Builder- Bury it!
Go to the Metwood website and look at there concrete pour-over system. It's the most user friendly system and it uses all light steel for the whole system. They have PE on staff and will help you with the design. If they don't have
status in your state,(there in Virginia) you may have the take there engineering to a P E in your state to get it stamped. They also have other very interesting structural plates that allow cuts in engineered wood items. I met the president of the company at the International Show in Orlando. He's a good guy. Good luck!
"If they don't have status in your state*, you may have the take there engineering to a P E in your state to get it stamped. "
When a PE stamps a drawing, they are certifying that THEY oversaw the preparation of the work, not that some PE somewhere did it. I realize that this sort of thing is done, but I wanted to point out that you may well encounter PEs who don't want to play that game yet are entirely competent in the task at hand.
When I review someone else's work for me to stamp, I check a lot of their calculations, make sure right assumption were made and make sure it overall "feels right". And I only do that for other engineers who work for the same company I do. Sight unseen, I'd be doing it almost from scratch myself.
That said, for early costing purposes, if a manufacturer will give you an enigneered design and can design for your local constraints (earthquakes, snow load, hurricane winds, frost protection, etc), go with it. Your local guy many design something a little more and or a little expensive to construct, but it should be in the same ballpark.
* I took a class for reciprocity in Alaska with two architects who were licensed in 49 states and were taking their arctic engineering for AK to add their 50th. Architects for McDonalds and they wanted to be able to stamp a drawing for ANYWHERE.David Thomas Overlooking Cook Inlet in Kenai, Alaska
If you go with ICF there are engineered products for the decking.
Within the last year or so FHB had an article on doing one. It was for a garage, but I don't know why a patio would not be similar.
Another thought, if it seems appropriate : I worked as an architect in the pacific northwest for many years. Besides rain, two other things we had a lot of were mountainous home sites and large trees.
It was not uncomon to be asked for something similar to what you're describing; a level parking place 8-10 above grade (or over grade sloping down at a real hurry). An engineer that I worked with for years would design a wood frame with short-span 4x10 beams and 2x PT decking, over which would be poured a conc slab. If you seal the concrete. the PT wood should last a very long time.
Andrew
This whole thing sounds to me like an expensive bad idea.
Concrete is a wonderful material on grade. Concrete way up in the air with usable space underneath? Jeez, it's dark and dank down there. It costs a fortune to support all that weight. It can be strong enough to park cars on top, which is the only thing it's really good for. If it's not a parking structure, this HO would get a much nicer result for much less money by building a big conventional deck. He wants a "stamped concrete" look, so the thing to do is try to find a reasonable substitute without the weight, or talk him out of it.
BTW, does anybody know about those prestressed beam and deck units that just stack up to make a parking structure?
-- J.S.