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I’ve got a hillside lot to design and build a house on. Because of certain limitations and challenges we are limited to a maximum footprint of 34′ x 50′. It looks as if we will have to go with a hillside walkout (walkout basement for us greybeards).
Because of the slope of the lot we are looking at building a deck overlooking the lake. I prefer a cantilevered deck because I dislike the thought and look of support columns. My other preference is to build the cantilevers with reinforced concrete; however, I don’t seem to be able to find any information on these systems. Everything says, “Consult an engineer.”
Does anyone know of any suitable books/WEBB sites, etc.? Does anyone out there have any experiences that they would care to share with me? I’m all ears.
Thanks,
Cliff. Johnston
Replies
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Hi Cliff,
How big a deck? More importantly, how far out would it cantilever?
Sorry, I don't know any sites but maybe someone else can help you there.
*Mad Dog,Looking at a deck extending out 12'-16' and anywhere from 20'-50' long. It all depends on cost factors.Cliff.
*That's a pretty good sized cantalope. Maybe you could cantilver some steel beams and box them in with treated or your choice of weather resistant wood, make it look like big timbers, run joists the long way, and have the deck boards perpendicular to the house, could be kind of interesting.Where are you located?
*Mad Dog,I'm in Texas. The lot is on Lake Granbury and from the road it faces north and the lake.The deck will be on the lower (ground) level. I was thinking of doing the cantilevers out of concrete so that they could be poured at the same time as the slab. The building site is on a ledge halfway up the hill from the lake. The ground slopes away at about 33 degrees from the ledge to the lake so a retaining wall could get pricey quickly - ergo, the cantilever thought.I am trying to use as little wood on the outside as possible. I've seen too many very expensive problems with termites, including a bullet that I dodged personally with termites down in Brownsville. When we started clearing the building site 2 weeks ago we dozed up an old stump and guess what? Termites. So I know that they are there, and if I ingore that, shame on me.Cliff.
*Don't take any chances. Those little woodbutchers can be a menace, though we have almost none up here in Wisconsin.If the deck is near ground level, perhaps you could cantilever SOME of it, off of posts that would be harder to see underneath it? Was your reason for not wanting posts the way they look or more lumber to expose? How high off grade do you expect the back of the deck to be?
*Mad Dog,I anticipate putting in a 3' retaining wall at the back edge of the slab to avoid any troublesome tight angles that could invite and harbor critters. Depending on location, the back edge of the deck could be 7'-9' off the ground - it will vary as the dropoff is not uniform. I could put in a series of small terraces which could look very picturesque; however, my parents are 80'ish, and we want to avoid as many steps as we can (the house will have a personal elevator too). Our original intention was to build a single level with a cathedral ceiling and bonus loft; however, when we finally cleared the site we realized that we would need about a 12' high retaining wall and kamikaze stairs to access the back of the lot and lake. The lot is a good size, approx. 135'L. x 117' frontage on the lake; however (my favorite word when discussing this lot), certain challenges restrict the building site to the right 1/2 as one faces the lake. Believe it or not, this is one of the best lots in the area as far as ease of access and building go - so everyone tells me. When we bought it 2 years ago the trees and brush were so thick that one couldn't see the lake or even more than 8'-10' from the road. Much of the growth was cedar thicket - the worst stuff I've ever had to log. On the positive side, the Brazos River Authority told me that the water quality at that point on the lake is the best. Other good info. is that I am smack dab between the 2 best fishing spots on the lake. One spot will be a 30 second boat ride from my dock and the other will be about 2 minutes. Not bad considering that we didn't know what we were buying!Cliff.
*If I may,Here in Kal la forn i a, we are held to some pretty strict standards. I think given your application the same would hold true.Even with a light weight mix, you have an engineering feet on your hands. Our building departments would not allow anyone without a engineering license to submit such a design or concept.With the general rule of thumb with respect to cantilevers, could you even achieve the proper ratio of dimensional framing lumber to the interior of the building to construct this deck? What effect will this exterior load have on the interior of the building when put under stress? (heavy winds, etc...)How about steel or concrete columns if pulp eating critters is the concern? Followed by some of the great composites available.Tackled a cantilevered project myself in San Fran a year ago. Great project. Existing cantilever, supported afterwards due to dryrot of the existing 2 x 12 joists. Timber Tech decking, tempered glass & redwood rail.
*See attachment, not that it helps your particular needs, just proud of my work.
*Mark,Good questions. I've been trying to get an engineer to look things over for the past month - can't even get them to call back for a small job. That's what prosperity does, I guess. I finally got antsy and decided to see if I could get some info. here to at least learn something about cantilevers and not have to ask a whole lot of dumb questions, if and when I ever get ahold of an engineer.Believe it or not there is no building code where the lot is. It is out in the county (as in not in a city) and the county has a hands-off policy. Is it good? Well there are miles of retaining walls around the lake and according to some of the contractors whom I have talked with, most of them have failed in some manner. Perhaps you guys out in California have finally got something right with all of your codes, etc. (tongue-in-cheek).Also, I was not intending to build the cantilever integral with the slab. I was thinking of a deep, boxlike counterbalancing weight along the back perimeter of the foundation slab. I could be talked into using cypress decking on top of the concrete cantilevers. I've used cypress before successfully. The only thing that affected it was a miner bee. The termites and carpentar ants left it alone.Cliff.
*Here's another.
*Mark,Nice pics. Nice work. Good reason to be proud.Cliff.
*Here's another.
*Hey since we've got a live discussion going, help me to see what it is you want to build. From what I gather, a 16'-0'' x 50'-0''(in the greatest dimensions) unsupported cantilevered deck. Preferably constructed of materials undesirable to structurally weakening pest.Therefore a cantilevered deck constructed of steel I-beams, counterbalanced on the interior end by a poured in place concrete footing to anchor the opposite ends of the I-beams. (on the interior end that is)Standing by...
*NYY-3, NYM-3, in the tenth.no attachments
*Mark,That's about it, although I was thinking of cantilevers made from rebar and poured concrete. The steel beams would be easier though. That's a thought.Cliff.
*Cliff,Yes, for what it's worth, any rebar configuration would not be sufficient! A slab of this size would require support. So your thoughts are now directed at whether to construct of available pressure treated materials or a pest free design much like many of our Roman & Greek fore-fathers have produced. Not to make light of your considerations, simply a global view. If a concrete deck is within the budget (long term budget just the same) I'm on the same page with you.High heels or wine stains surely wouldn't be a problem. I really like the way the i Timber Techturned out. If the concrete deck becomes a reach, consider the composites if not the exotic deck materials as well which I have worked with. Photo's in progress.Damm, Yankees in twelve!
*Mark,We like to go barefoot so my wife is a little shy of wood. May have to go to some support columns and pour a light weight deck. I guess I could plant some decorative vines to hide the columns.Appreciate the feedback and looking forward to your photos.Cliff.
*One question. Have you got any drawings for these potential engineers to look at, or are you using words to describe your ideas?drawings are like a big fat piece of herring...
*A 16-foot cantalever is no small feat. You say that you cannot get an engineer to call you back - that may be because they are anticipating that you are not ready to pay what it costs to have this designed properly. I would expect to pay $10k or more for the engineering on this one. This is way more than engineering trusses or some other standard structural member (like sizing glulams or desinging shear walls). This is a serious custom design with a lot of liability implications. Remember, that engineer is risking his license, livelihood and personal assets each time he uses his stamp. You'd better bet that deck will involve some large pieces of steel. Decks are especially troublesome because of the potential that they would be loaded with a big crowd of moving people. I had some friends that designed a similar catalever overhang for Bank One Ballpark in Phoenix, AZ. The deck was for a TGIFridays that is inside of the ballpark. They wanted to add 10' or so of deck space for additional tables, but not remove any of the money-generating seating below with columns. They used some HUGE steel beams with an incredible connection detail to columns behind the stadium seats (seemed like 100 or more 1" diameter bolts on the connection plate). That was a serious engineering and construction challenge, but was worth the money for the owner. I am not sure if having this deck catilever is worth what it is going to cost you to do it correctly and safely. Why not place concrete columns using sonotube to support building a deck using more traditional methods? Seems like it would be a whole lot cheaper and easier for you to accomplish without spending 10s of thousands.Just my opinion...Sami
*also no reason why the support columns could not be very decorative. Maybe a series of cast in place, reinforced concrete arches that run parallel to the structure. Also, if I understand correctly, the slope of this site gives you 8' or so fall in 16' run. Unless my math is screwy you have a steep hillside site at around 22 degrees. Are you not going to be building on piers, underpinning, grade beams, retaining walls etc?It seems that your concern with not being able to find an engineer to solve the problem of the cantilever is premature. There are many other issues which need to be addressed simply to make the house cling to the hill, which involve complex engineering and cost control, which you will probably find through a good builder. I would say you need to find an architect first, followed by a builder, have a pow-wow with them to design and control costs, and then they will coordinate an engineer.But then, I's just a know-nothin rookie. Best of luck to you. Remember to rip the lips off those big ones... Oughta build that deck so you can cast to your honey hole in your slippers..
*What about a large concrete column located in the center of the deck at the outer edge. That would support a properly sized piece of steel to supportthe deck. The steel woul dbe canteleved equaly from each side. I am not an engineer but the idea seem slike it would work. If the deck is 50' wide the cant woul d be 25 on each side. Just a thought.
*What about a large concrete column located in the center of the deck at the outer edge. That would support a properly sized piece of steel to support the deck. The steel would be cantelevered equally from each side. I am not an engineer but the idea seem like it would work. If the deck is 50' wide the cant would I be 25 on each side. Just a thought.
*Appreciate all the feedback, men.We're out in the boonies. Engineers are a scarce commodity out here.I did find a copy of Porches, Decks & Outbuildings - The Best of Fine Homebuilding. Pages 82-85 show something attractive that I can live with happily. The cantilever appears to be modest, 6' or so. The slab is 6" thick with #4 rebars on 12" centers. As of now we've rethought a few things and are going to reposition the house on the lot slightly which will reduce the need for such a large deck. From what I saw in the FHB article, we'll make the retaining wall part of the deck support system and cantilever only 6' or so. I guess that we may have to go into the big city, Fort Worth, and find an engineer there. Bear in mind, guys, I need an engineer to design the slab and do the soil work, etc.. It never was a matter of not wanting to find and pay one. They are just too busy here. It took me almost 4 months of hounding a surveyor before I could get one out to the lot; then it cost me $1,200. There were problems with the original development survey. They are overworked in this area and take the larger, more profitable jobs first. Hopefullly the building slowdown will start to benefit me.I would also like to state my original premise that I wanted some feedback on cantilevers so that when I do talk with the engineer I am at least semi-prepared with some reasonable idea of what can be done and an idea of what we want designed. I don't want to sit down with the meter running and waste his time and my money (it's a close budget). I'm getting there thanks to you all.Appreciate the feedback (keep it coming),Cliff.
*I worked on a cantilevered deck in Connecticut many, many, many moons ago and I believe it stuck out over the ravine a good 12 feet. We pushed I-beams out over the exterior bearing wall but I'm not sure I remember exactly how the back end was anchored. I think it was another steel beam, perpendicular and anchored sidewall to sidewall, to which the canted beams were attached.Do you (does anyone) think that on Cliff's slab, that I-beams can be anchored in and through the slab in that method but with the perpendicular beam back in the slab anchored by a sufficient mass of concrete pour (with rebar and anchors inserted) to resist the uplift stresses of the cantilever and without causing cracking along the line of each buried beam? Or would you even need a perpendicular beam if you had a poured bond beam encasing the ends of the canted beams?
*b TVMDCCliff, An engineer I use normally starts with a factor of 1.5 for the supported part of a cantilever and then adjusts its length/height by the required load. If your house depth is 34', the cantilever could theoretically be 22' (22 x 1.5 = 33).Glulam beams would be a natural ONLY IF WOLMANIZED or Paralams, again, WOLMANIZED due to the extreme danger of dry rot/termites if non-wolmanized material is used.However, you must have an engineer calc the beams' sizes and quantity needed and the purlins, sub-purlins, etc..One other small detail: access. 56' long beams (34'+22') don't fit on a pickup. Cranes and flat beds don't fit easily on tight mountain roads, and a crane-on-barge may not be an option either.One other possibility would be to use diagonal support posts starting at the outside of the deck and returning to the footing, or cable guys running up to the roofline.
*so how about cantilevered trusses? Sound cheaper to me in the end. Don't know much about truss design, but it would seem to be a logical alternative to doing an expensive bit of reinforced concrete. I bet McMillan (TJM)could provide the engineering, do the fabrication and ship to your site. They may even give you an estimate, or feasability if you contact them. That's the impression I have of what they are trying to do with their customer service...
*If you want to see a lot of cantilevered concrete decks, check out Frank Wright's contemporary stuff, most notably Falling Water. They have recently been trying to restore Falling Water because it is Falling Down. The cant. conc. decks have been slowing creeping, that gravity thing, and they are now putting support columns under it. I read that the contractor doubled the amount of rebar Frank wanted when he wasn't looking - still didn't work. I would reccomend steel. A well engineered steel system can do a lot of work without the mass of wood beams.
*Toe,Glad to hear from you as it was the cantilevered deck shots on a Falling Water segment on TV that got my wife and I to thinking about using that construction technique on our new home. Kind makes us stop and think twice about how great(?) Frank Lloyd right really was. He did have some appealing designs; however, I've heard quite a bit about structural failures on other projects of his too. It's one thing to fantasize, but an entirely different thing to make it work - and we want our deck to work.Cliff.
*If you are attempting to emulate Falling Water, then you should know that Taliesin West is still in business and they can design a house for you. See thier web site: http://www.franklloydwright.org
*Toe? Ahem. Anyway, I don't want to cast an ill light on F.L.W. He was an innovator and a genius. That doesn't mean his stuff would always work (his roof are notorious for leaking too), but he paved the way for a lot of great ideas, both practical and idealogical. If you have the time and means, keep on with your design dreams. They will inspire the rest of us. Good luck.
*We're not trying to emulate Falling Water. We do like some of FLW's design ideas though, and cantilivered concrete decks hold an appeal for us. I specified concrete - first I'm an old union cement finisher by training and trade although I traded the trade in sometime ago for a university degree and a white collar job that I now put in 60-70 hours/week at - not complaining; second, because I feel that reinforced concrete will perform best for me given the hillside with the "building" ledge perched up by the road and the lot falling off somewhat steeply to the lake.I like steel reinforced concrete. I spec'ed, built and poured our present pool with decking and extensive exposed aggregate patios 8 years ago. "Pool" men told me that all decks and patios in this area cracked within 2 years. Well, it's been 8 years now, and I've yet to see the first crack other than at an expansion joint. I had some good union concrete men teach me a few basics many years ago, and they work. Simple things like having a good base and tamping it, tying steel on chairs instead of using wire mesh. Using 2x6's for forms and pouring a 5" slab with 3500 psi minimum concrete. I cringe when I see what some contractors are getting away with today, and the lousy results after a few years bear me out. Hey, designing and working with concrete can be both rewarding and fun, if it's done properly.We're on our second architect for this project. This first one said that it was beyond his abilities once he looked at our preliminary plans and spec's. He then recommended an architect in Dallas who should have our packet of information by now. Again, we are not trying to cut out an architect and/or engineer. We simply want to go into a meeting with some realistic ideas that can be accomplished on the site.Yes, this is our "dream house"; however, it will be somewhat modest by new construction standards on Lake Granbury. I will also be the general contractor and will be doing all of the finishing work on the inside. I used to have my own construction company some years ago, so I feel "up to it".I don't have a problem building forms, tying steel and pouring concrete - I rather enjoy it. So we're back to a steel reinforced concrete cantilevered deck. Anyone checked out that article that I referred to on the 12th? Anymore ideas out there, guys? Thanks, Teo. The dream goes on. Keep the ideas coming.
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I've got a hillside lot to design and build a house on. Because of certain limitations and challenges we are limited to a maximum footprint of 34' x 50'. It looks as if we will have to go with a hillside walkout (walkout basement for us greybeards).
Because of the slope of the lot we are looking at building a deck overlooking the lake. I prefer a cantilevered deck because I dislike the thought and look of support columns. My other preference is to build the cantilevers with reinforced concrete; however, I don't seem to be able to find any information on these systems. Everything says, "Consult an engineer."
Does anyone know of any suitable books/WEBB sites, etc.? Does anyone out there have any experiences that they would care to share with me? I'm all ears.
Thanks,
Cliff. Johnston