Folks, I’m designing my next house with an open (roofed) veranda over a garage. I can’t seem to envision a good way to create the veranda floor (garage ceiling) and make sure it is weather-proof. Do I simply frame it with BCI’s and plywood subfloor covered with Bitchethane (or equivalent), or pour a concrete floor over wood or steel framing, or …? My wife likes a terrace-like finish of flagstone on a sand base, but she may be talked into slate tiles if necessary. We’ll be building at 8500 feet elevation where the freeze-thaw cycle can be maximum. Thanks in advance for your help.
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Let's start with the formalities.
Howdy,
Now that we know each other better, let me get personal.
Do you realize this can be a very expensive proposition?
Are you willing and able to do it right? (Meaning spend money to do what might seem like over building)
I will entertain any option from moderately priced to expensive (cheap, for this application, is probably out of the question). Heck, this is the design stage, so I'm looking for options....
I think I have a detail drawing or two but it wil take time to find an I am in midst of a couple designs right now so it may take a few days. One reason why I asked first before I put in too much.
Basically, you will need an over structured garage roof frame because of the weight it will hold. If snow may be added to that, you could be looking at 150#/sf engineering.
Then the roof membrane will need to be a real waterproof roof with good flashings. I see too many people try something like this with just simple plastic or vapor bar. You might be tempted to use bituthene and that 'might' work. If it were me, I would use a minimum of two ply, carefully applied. They now have a form of the ice and water shield that is nearly double thickness for application to concrete basement walls for underground water proofing.
My detail drawing is from the sort of work we did on galleries approaching museums and other public buildings where tiled walkways were actually roofs over interior space. govt work is always overdesigned, of course but if I find it it will give you some thoughts. Sometimes drainage membranes were included to facilitate drainage of moisture that made its way through the masonry surface. The water has to have a place to go or it will make a place to go, often where you don't want it. You don't want it locked into a slow drainage pattern or it will freeze and break up your surface. So a drain plane is an absolute, either on top of the tiles or between the masonry and the waterproof roofing.
There were poly meshes and various acrylic coatings used for these applications once. They were just coming into use when I got out of that sort of thing. Most of my work was with hot asphalt mopped plies. On surface flat roofs, most of that has been replaced with EPDM or modified torch down products.
The big killer of any of these is friction and UV rays. You won't have to worry about the UV but the friction could be a concern. Suppose that you put down ice and water shield and a couple inches of sand, then the bed of tiles. The sand would allow movement that could wear pinhole leaks eventually. So you would want another ply of loose laid material such as simple tarpaper to barrier that.
Some of these jobs can add as much as eight inches of elevation above the plywood so you need to be thinking about how to make allowance for that in the transition to the interior floor as you plan your framing elevations.
There is a temptation to think in terms of saving a buck because after all, it is only a garage under there, not expensive living space. Don't think that way though. A small leak can make a big rot problem. Rotting roof framing that extends under your living space can provide you with hours and hours of worriment. And once you have finished with this job, it will be tremendously expensive and difficult to reopen it for repairs. Hence the over-design on the govt jobs.
I'll be subscribing this discussion and look for the details later when I get into that area.Excellence is its own reward!
Thanks. Seems like my thinking is along the same lines. Hearing it from someone else helps, as well as picking up a few tidbits (e.g., the friction concern). I will continue my research, and continue to monitor this thread. Any others care to add knowledge here? Thanks again. Cheers.
Edited 9/4/2002 9:47:43 PM ET by GreenStone