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I have a 3” slab of concrete. I have a header board running nearly 20 feet across my house and no posts under it. (The roof slopes from about 9 feet down to its posts at the 3” slab ends at just about 7’11”.) the 3 exterior posts are 4x4’s with 2x6’s running horizontally and joists are 2x4’s.

  • My hope is to reinforce with some new 6x6 posts (3 under header board and 3 on exterior). Additionally I know I need better concrete, anxious. So can I put concrete cylinder tubes on top of the slab and anchor atop those? (If I made them 18-24” deep?
  • Secondly, if the pists are alm6x6’s and there’s 6 of them across 20 feet long , do I need better joists than 2x4’s ? Can 2x4’s running across 12 feet from header to external post carry live load of upwards to 1000 pounds?

I’d like to strengthen the cover so it can be walked on and sat on to watch sunsets. Kinda make it a ‘porch’

No idea about frost or snow load. I live in New Mexico (close to albuquerque) What happens if a footer of say 24” is placed atop the 3” slab at the beginning/middle/end (approximately 10 feet apart

O ——10’ —— O —-10’—- O

10ft

O —-10’—- O —— 10’— O

Placed at 1 foot 11feet & 21 feet

enter image description here

Is this setup not ok, because the slab is only 4” thick?

Niall C.
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  • Do you know the snow load and the frost depth for your area, if any? 2x4s are good for four maybe five foot spans for weight bearing. 3 inch cement slab is only good for walking on, will need to cut sections out and put in proper footers. Your local building department will be able to tell you exactly the size of joists, beams, and footers you need to be safe. – crip659 Apr 14 '23 at 21:44
  • Use the [edit] link underneath your post if you want to update it with new information. Thanks and welcome to the site! – Niall C. Apr 15 '23 at 17:40

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