Concrete Roof system for any style roof

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2 years 3 weeks ago #58 by Greg McDonagh
Greg McDonagh created the topic: Concrete Roof system for any style roof
Recently we launched a campaign demonstrating the simplicity of the Spider Tie concrete roof system. We simply use the wood truss roof as a mold/form and shoring for a 3-4" thick concrete roof. At first the initial concern was could a typical wood truss roof package support a concrete shell like this. 3" of concrete weighs 38 lbs per sf. 4" weighs 50 lbs.per sf. The engineers said with out a doubt no problem. They explained that some minimum snow load requirements through out the country exceeded the weight of our concrete shell by 3 times- 150 lbs per square foot.
The cost difference to add this additional load on the trusses was nominal. For example here in Park City Utah the snow loads are 38 lbs per sf. By adding the additional dead load plus 15 lbs per sf more it only increased the truss package cost by $300.
On other projects we found the steeper the roof the easier the pour was. The set up process takes about 2-3 days. We pour the roof in one day in 4' lifts from one side then the other maintaining equal loading on the trusses. We add Super P to ensure as faster set time.
Once the shell cured it seemed that it was semi self supporting. No sagging or stress points could be found through out the whole roof from inside. Total materials cost came in at about $4.28 sf. (spider ties, rebar, concrete, additional plywood on top and bracing)
We filmed a video of the process. you can see it on You Tube at

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