A massive rebuild is needed in Los Angeles after devastating wildfires wiped entire neighborhoods off the map, and local architect John Cordic says the city can be reconstructed in a couple years ... as long as city officials get on board.

John joined us on "TMZ Live" Monday and we asked him the question on a lot of folks' minds ... how long is it going to take to rebuild L.A.?!?

With over 12,000 structures burned to a crisp in the Palisades and Eaton fires, it's a monumental task that will require a Herculean effort ... but John says architects and engineers are ready to get to work ASAP ... and he thinks 2 to 3 years is the best-case scenario.

The issue ... John says building permits that used to take several weeks to obtain can now take years ... and that process needs to be streamlined if L.A. wants to avoid a long rebuild.

John says it often takes longer to get permits in L.A. than it does to actually build the house ... and he explains how a bunch of government agencies bog down the process, especially for folks in Malibu and the Palisades, who need to rebuild along the coast.

The good news ... John says we can make obtaining permits simple again without rewriting a bunch of codes or creating a new commission ... and he gives us a quick fix.

And in some fortunate timing, California Gov. Gavin Newsom announced an executive order this weekend ... he's waiving some environmental requirements for building permits for businesses and homeowners, in order to speed up rebuilding efforts -- and he's promised to look for more ways to get things done faster. The executive order also protects homeowners from price-gouging.

John says builders are ready to make L.A. rise from the ashes ... if the city adapts.

Watch "TMZ Live" today ... check your local listings.