Old house, new deck
January 11, 2022 3:30 PM Subscribe
I have a super old house (single story) and the flat roof is apparently made out of jello. My roofer says don’t walk on it, and the architect I called said building a roof deck would be a six figure undertaking. I am really, really interested in hanging out on aforementioned jello roof, as the view is incredible. I’m wondering about if I could create some sort of scaffolding that basically has legs on both sides of the house supporting a metal deck. Or, if anyone else has other creative ideas that don’t involve spending $$$?
You could build a steel superstructure spanning over the house (as you describe) but the building department is likely to be an obstacle.
Setting that aside for the moment, steel mezzanines are fairly common in industrial applications, are very similar to what you describe, and cost roughly $14-20 per square foot (smaller jobs being the $20, big ones being less). Plenty of structural steel fabricators have experience with them, and the engineering is fairly straightforward (you would need a structural engineer to design this).
…but in aggregate I’d do as furnace.heart suggests.
posted by aramaic at 3:56 PM on January 11, 2022
Setting that aside for the moment, steel mezzanines are fairly common in industrial applications, are very similar to what you describe, and cost roughly $14-20 per square foot (smaller jobs being the $20, big ones being less). Plenty of structural steel fabricators have experience with them, and the engineering is fairly straightforward (you would need a structural engineer to design this).
…but in aggregate I’d do as furnace.heart suggests.
posted by aramaic at 3:56 PM on January 11, 2022
I think you may want to consider an off label use of a backyard shed.
Alternatively, your interests align somewhat with those building tree houses or zip line platforms.
posted by oceano at 4:22 PM on January 11, 2022
Alternatively, your interests align somewhat with those building tree houses or zip line platforms.
posted by oceano at 4:22 PM on January 11, 2022
Huh. Is it possible that what you've got is a membrane roof, and that's why you're not supposed to walk on it?
Our membrane-roofed building came with a 'floating deck'. Basically, a wooden raft, with a decorative railing. It just hung out on the roof, distributing weight, and you could hop onto it without stepping on the membrane.
posted by feral_goldfish at 4:53 PM on January 11, 2022 [5 favorites]
Our membrane-roofed building came with a 'floating deck'. Basically, a wooden raft, with a decorative railing. It just hung out on the roof, distributing weight, and you could hop onto it without stepping on the membrane.
posted by feral_goldfish at 4:53 PM on January 11, 2022 [5 favorites]
Do as furnace.heart suggests. If you know what you want and can draw a reasonable plan/sketch of it, maybe try looking for a draughtsperson rather than an architect, as they won't charge an arm and a leg. You will also need an engineer to design/sign off the structural aspects. If you are OK with DIY, this is absolutely the way to save money on a project like this - I'm almost finished building a large roofed deck onto the back of our house and have done every single part of the building myself. It's a lot of work, but rewarding ($ and otherwise) and you get to make sure all the little things are exactly how you want them. I'm in a different country, so costs may be wildly different, but our total material and compliance costs will end up around $20k, with the cheapest quote from a builder being $45k to build the same thing. Doing it yourself also means you can spread the cost over time by only ordering materials as you need them.
Depending on the structure of your house, it may be possible to attach 'legs' to the walls to support a deck, but you may have to brace down to the ground if the house won't support that much weight. It may also be possible to reinforce sections of the roof for support. This depends a great deal on the size of deck you want, because of both weight and wind loading. An engineer will be able to guide you on this and it's probably worth talking to them before designing the deck. Before speaking to anyone else, talk to the local authority that will need to approve the deck - contrary to common belief, they are very likely to be helpful if only because it's easier to be helpful now than difficult later.
For something this conspicuous, definitely do not try and work outside the building codes - you will definitely get comments if not complaints from one or more neighbours and that will lead to a world of pain for you. One of our neighbours constantly complained about our deck to the extent the local authority told us they would not respond to any further complaints from them, as they could clearly see the job was being done right and as approved.
posted by dg at 5:33 PM on January 11, 2022
Depending on the structure of your house, it may be possible to attach 'legs' to the walls to support a deck, but you may have to brace down to the ground if the house won't support that much weight. It may also be possible to reinforce sections of the roof for support. This depends a great deal on the size of deck you want, because of both weight and wind loading. An engineer will be able to guide you on this and it's probably worth talking to them before designing the deck. Before speaking to anyone else, talk to the local authority that will need to approve the deck - contrary to common belief, they are very likely to be helpful if only because it's easier to be helpful now than difficult later.
For something this conspicuous, definitely do not try and work outside the building codes - you will definitely get comments if not complaints from one or more neighbours and that will lead to a world of pain for you. One of our neighbours constantly complained about our deck to the extent the local authority told us they would not respond to any further complaints from them, as they could clearly see the job was being done right and as approved.
posted by dg at 5:33 PM on January 11, 2022
One other thing I thought of to consider while planning a project like this; will its presence inhibit the replacing of your roof when it reaches the end of the natural lifespan? No roof lasts forever; encasing it or building over it may indeed cost more money in the long run when that occurs.
If your roof is nearing the end of it's life, this can change the calculus of what you do or don't do, or even how you execute adding the deck to allow for its eventual replacement. I would be very concerned that adding a structural element like a deck on top of a roof, could increase the cost of that roof needing to be replaced in line with the figure you're concerned about spending.
posted by furnace.heart at 5:40 PM on January 11, 2022 [4 favorites]
If your roof is nearing the end of it's life, this can change the calculus of what you do or don't do, or even how you execute adding the deck to allow for its eventual replacement. I would be very concerned that adding a structural element like a deck on top of a roof, could increase the cost of that roof needing to be replaced in line with the figure you're concerned about spending.
posted by furnace.heart at 5:40 PM on January 11, 2022 [4 favorites]
Something cheap that spreads out your weight is another option. Shipping pallets or plywood? (Removing them or tipping them up when not in use is probably a good idea.)
posted by eotvos at 7:27 PM on January 11, 2022
posted by eotvos at 7:27 PM on January 11, 2022
Is it possible that what you've got is a membrane roof, and that's why you're not supposed to walk on it?
Ya, first thing is to determine specifically why it is recommended to not walk on the roof. The options for "substructure won't support a person" and "membrane/waterproof layer can be damaged by traffic" are pretty different. If it is the latter, and considering contemplating the view is the desired activity, it might be pretty cheap to have a small (say 8x8 foot) section of the roof modified to accommodate that use. Basically just enough space for a small table and a couple chairs.
Alternatively, do you by chance have a exterior door at the rear of the house that doesn't have a roof over it? I'd be tempted to build a mud room to shelter the door that just happened to incorporate a small roof deck. Unless you live on the side of a cliff or something it certainly wouldn't run six figures unless it somehow requires you to update other thing in the house. It's the kind of thing one could DIY for mid to high four figures if roof access was via ladder (stairs are pretty expensive and could run a couple thousand all by themselves).
posted by Mitheral at 2:47 AM on January 12, 2022 [4 favorites]
Ya, first thing is to determine specifically why it is recommended to not walk on the roof. The options for "substructure won't support a person" and "membrane/waterproof layer can be damaged by traffic" are pretty different. If it is the latter, and considering contemplating the view is the desired activity, it might be pretty cheap to have a small (say 8x8 foot) section of the roof modified to accommodate that use. Basically just enough space for a small table and a couple chairs.
Alternatively, do you by chance have a exterior door at the rear of the house that doesn't have a roof over it? I'd be tempted to build a mud room to shelter the door that just happened to incorporate a small roof deck. Unless you live on the side of a cliff or something it certainly wouldn't run six figures unless it somehow requires you to update other thing in the house. It's the kind of thing one could DIY for mid to high four figures if roof access was via ladder (stairs are pretty expensive and could run a couple thousand all by themselves).
posted by Mitheral at 2:47 AM on January 12, 2022 [4 favorites]
Consider the possibility that the existing roof may need repair or replacement at some time. Is it worthwhile to do that as part of your project? If not, how will you access the roof for repairs if you build over top of it?
posted by mightshould at 3:43 AM on January 12, 2022
posted by mightshould at 3:43 AM on January 12, 2022
Yes you need more details on the 'dont walk on' it reason. Do you know how much rain or snow weighs? Way more than a person, and that's loads any normal roof should be made to handle.
Is it about to fail?
I'm assuming your flat roof has at least some walls holding it up that might extend beyond the height of the roof? You could add beams to that, over the top of the roof.
I'd honestly get a 2nd opinion from another architect and get way more details.
You may also shrink the size of the deck down.
posted by The_Vegetables at 7:36 AM on January 12, 2022
Is it about to fail?
I'm assuming your flat roof has at least some walls holding it up that might extend beyond the height of the roof? You could add beams to that, over the top of the roof.
I'd honestly get a 2nd opinion from another architect and get way more details.
You may also shrink the size of the deck down.
posted by The_Vegetables at 7:36 AM on January 12, 2022
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I am a huge fan of unconventional building projects, and have engaged in some...uh...light flouting of code. I would not do this. Especially as most code issues are complaint driven: if you're building something big and weird, you're going to get complaints if they are valid or not. You have to have conspicuous things done correctly.
If you want to save money, learn how to do it yourself. Most building costs are labor. Find a DIY friendly architect (this is hard to do) to draw you up detailed, to code plans to retrofit your roof with a deck. Take the plans to your local planning office and have the plans approved. Follow said plans. Good plans are not hard to follow when it comes to building, and 'building code' is only scary in totality: if you talk to your local planning office early in the process, they are not an adversary, but an aid. There is usually a couple folks in each department who want to see weird things get built, and get pretty excited when you bring offbeat stuff to them.
That's how I found out that my 2nd story greenhouse was perfectly permissible under our local code, by exactly two inches in height. It also helped the process when some dipshit neighbor complained to the code office about it, and I just send them the email chain of confirmations from their fellow employees citing that it was all cool.
posted by furnace.heart at 3:53 PM on January 11, 2022 [13 favorites]