A build can take many months, and rates move in that time. FHA's Construction to Permanent rules deal with that directly: a written agreement on how the rate behaves during construction, a ceiling you qualify at, and fixed deadlines once the house is finished.
During the construction period the interest rate may be variable. The lender and borrower must sign an agreement that:
States the range in which the rate may float during construction.
Documents when the rate gets locked in.
Says the permanent mortgage will not exceed a specific maximum rate.
Lets you lock a lower rate if one is available and you have not already locked.
The underwriting side of that ceiling matters: the lender must qualify you at the maximum rate the permanent mortgage could carry. If the payment at the top of the range does not fit your debt-to-income, the file does not work, even if today's rate would.
At closing, after any land purchase is paid, the rest of the loan goes into an escrow account and is paid out as construction progresses. The lender must get your written authorization for each draw before paying the contractor. When construction is done, the escrow is closed out and any money left goes to reduce your principal.
You also sign a disclosure at closing saying the mortgage is not eligible for FHA insurance until after a final inspection or the Certificate of Occupancy, whichever is later. The construction rider and loan agreement must end all special construction terms at conversion, leaving only standard permanent terms.
Endorsement. The mortgage must be endorsed for FHA insurance within 60 days of the final inspection or CO, whichever is later.
Amortization. Regular principal and interest payments must begin no later than the first of the month following 60 days from the final inspection or CO date. Before endorsement, the lender also pulls a title update showing no liens other than the mortgage, and documents that the construction money was fully drawn.
How the loan amount is set in the first place is on land and your loan amount. Building in a rural area? USDA has its own single-close version with different builder and reserve rules at USDAConstructionMortgages.com.
Source: HUD Handbook 4000.1 (Update 17, 11/26/2025), section II.A.8.j Construction to Permanent, parts vii Mortgage Interest Rate, viii, ix Escrow Account, x, xi Endorsement and xii Start of Amortization. Lender overlays may apply. Not a commitment to lend.
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