Brendan T. Cavanagh
Executive Vice President and Chief Financial Officer at SBA Communications
Thank you, Mark. Good evening. SBA had another great quarter with financial and operating results ahead of our expectations and continued strong momentum into the end of the year. Total GAAP site leasing revenues for the third quarter were $535.5 million and cash site leasing revenues were $525.1 million. Foreign exchange rates were generally in line with our previously forecasted FX rate estimates for the quarter. They were a tailwind though on comparisons to the third quarter of 2020, positively impacting revenues by $3.2 million on a year-over-year basis.
Same tower recurring cash leasing revenue growth for the third quarter, which is calculated on a constant currency basis, was 3.6% over the third quarter of 2020, including the impact of 2.5% of churn. On a gross basis, same tower growth was 6.1%. Domestic same tower recurring cash leasing revenue growth over the third quarter of last year was 5.7% on a gross basis and 3.3% on a net basis, including 2.4% of churn.
Domestic operational leasing activity or bookings, representing new revenue placed under contract during the third quarter, was at a similar level to the second quarter, which had represented the highest quarterly level since 2014. Even with this high level of execution, our domestic new lease and new amendment application backlog continue to grow during the quarter and finished the quarter higher and at a new multi-year high.
These backlogs support our expectations for continued strong domestic operational leasing activity throughout the balance of this year and into 2022. During the third quarter, amendment activity represented 45% of our domestic bookings with 55% coming from new leases. The Big 4 carriers of AT&T, T-Mobile, Verizon and DISH represented 96% of total incremental domestic leasing revenue signed up during the quarter.
Internationally, on a constant currency basis, same tower cash leasing revenue growth was 5.2% net, including 2.7% of churn or 7.9% on a gross basis. International leasing activity increased again quarter-over-quarter and was the highest in over a year. Churn grew some in the quarter as well and is anticipated to increase further as we experienced the impact of carrier consolidations and other network and contract modifications in Central America.
In Brazil, our largest international market, we had another quarter of increased leasing activity. Gross same tower organic growth in Brazil was 9.5% on a constant currency basis. During the third quarter, 84.5% of consolidated cash site leasing revenue was denominated in U.S. dollars. The majority of non-U.S. denominated revenue was from Brazil, with Brazil representing 11.7% of consolidated cash site leasing revenues during the quarter and 8.4% of cash site leasing revenue, excluding revenues from pass through expenses.
Tower cash flow for the third quarter was $428.1 million. Our tower cash flow margins remained very strong with the third quarter domestic tower cash flow margin of 84.6% and an international tower cash flow margin of 69.9% or 90.8% excluding the impact of pass through reimbursable expenses. Adjusted EBITDA in the third quarter was $407 million. The adjusted EBITDA margin was 70.3% in the quarter. Excluding the impact of revenues from pass through expenses, adjusted EBITDA margin was 74.7%. Approximately 97% of our total adjusted EBITDA was attributable to our tower leasing business in the third quarter.
During the third quarter, our services business produced record results for the second quarter in a row with $53.8 million in revenue and $12.5 million of segment operating profit. Activity levels remained very high in the quarter and backlogs also continue to grow, finishing the quarter at another all-time high level in our company's history. Based on our strong third quarter and the growing backlog, we have increased our full year 2021 outlook for site development revenue for the third quarter in a row. Now expecting $200 million of site development revenue at the midpoint of outlook range.
AFFO in the third quarter was $302.5 million. AFFO per share was $2.71, an increase of 13.9% over the third quarter of 2020. During the third quarter, we continued to expand our portfolio, acquiring 144 communication sites for total cash consideration of $57.1 million. We also built 87 new sites in the quarter. Subsequent to quarter end, we have purchased or are under agreement to purchase approximately 1,700 additional sites in our existing markets for an aggregate price of $231 million, including approximately 1,400 sites and approximately $175 million related to the previously announced deal to acquire towers from Airtel Tanzania.
We anticipate closing on these sites under contract by the end of the second quarter of next year. And we anticipate the Airtel Tanzania transaction to close in stages starting in the fourth quarter of this year. Consistent with our prior outlook, our updated 2021 outlook assumes that the Airtel acquisition closes at the end of the year. And thus, we have included the entire purchase price in our outlook for discretionary capital expenditures, but we have included no revenue or tower cash flow associated with these assets.
In addition to new tower assets, we also continue to invest in the land under our sites. During the quarter, we spent an aggregate $11.6 million to buy land and easements and to extend ground lease terms. At the end of the quarter, we owned or controlled for more than 20 years the land underneath approximately 72% of our towers. And the average remaining life under our ground leases, including renewal options under our control is approximately 37 years.
In this afternoon's earnings press release, we included our updated outlook for full year 2021. Notwithstanding our assumption of weaker fourth quarter foreign exchange rates, our updated outlook includes increased expectations for site leasing revenue, site development revenue, tower cash flow, adjusted EBITDA, AFFO and AFFO per share. These increases result from high services activity levels with our carrier customers, anticipated timing shifts in domestic consolidation churn, reduced cash interest expense as a result of recent refinancings and the impact of recent share repurchases. We anticipate that our strong domestic leasing bookings during the second and third quarters will be supportive of improved incremental organic domestic leasing revenue in 2022, which we will share on our fourth quarter earnings call.
With that, I will now turn things over to Mark, who will provide an update on our liquidity position and balance sheet.