When the crossing is the only way in.
A private timber bridge is a length of driveway that happens to be over water. Span, load, foundation and what the creek does in a flood get settled before a timber is cut.
Four crossings, one question underneath them.
What happens to the drive when the water comes up.
The ranch drive over a seasonal draw — dry ten months, impassable for the other two. The creek that cuts a property in two, leaving forty acres worth only what you can get equipment onto. Back-pasture and island access, short but carrying a tractor and stock trailer. And the shared private drive that is somebody's only route out.
Not all of them need a bridge. A low-water crossing is the Texas default because it is cheap, and on a draw that runs hard a few days a year it is the right buy. What it costs you is the days the drive is under water, and the fill it puts in the channel for the next flood to take back out. A bridge is what you build when neither is acceptable.
Two numbers decide most of the design.
How far it reaches, and the heaviest thing that will ever cross it.
Span. Solid sawn timber stringers generally run out somewhere around 26 feet. Past that you are into glulam, which reaches further, or an intermediate pile bent that turns one long span into two. Most Texas creek crossings are wider than 26 feet, which is why the usual answer here is a multi-span, pile-supported bridge — though a clear span carries one real advantage, and it is a permitting one.
Load. HS-20 is the common benchmark for a vehicular private bridge: 72,000 pounds on three axles. HL-93 is the modern AASHTO model, pairing a design truck or tandem with a distributed lane load. Capacity is never one number, because axle spacing changes what a deck can carry, so a 5-ton rating and a 72,000-pound rating can both be true of the same structure.
Often somebody else supplies the number. The International Fire Code requires a bridge forming part of a fire apparatus access road to carry fire apparatus, to AASHTO standards, with load limits posted where the fire code official requires it.
The material suits the crossing, not just the budget.
Three reasons unrelated to how it looks.
It keeps the drive usable during the flood
An elevated deck is passable while the creek is up. A low-water crossing is passable once it drops, and only after the approach is regraded.
It puts nothing in the channel to be washed out
Fill and culvert pipe are what high water goes to work on. A pile-supported span leaves the channel alone, so the maintenance bill falls away instead of repeating.
It handles wetting, drying, and a ranch road
A crossing lives in the alternately wet and dry band that opens joints in rigid materials; properly specified timber moves and carries on. It can also be set with equipment that will actually get to the site.
Two specifications decide whether it lasts.
Say the use category, not "pressure treated." The American Wood Protection Association classifies treated wood by exposure. UC4A is general-use ground contact and covers fresh water; UC4B is heavy-duty ground contact for severe environments, critical components and salt water splash zones; UC4C is extreme duty, and is the category that explicitly names land and fresh water piling and foundation piling — what goes under a creek bridge. Retention is set by the AWPA commodity specification for the member, so the piling spec is a different number from the deck spec — which is the whole point of naming the category rather than the treatment. Lumberyard "pressure treated" is a lighter deck-grade category: invisible on the truck, decisive in fifteen years.
The hardware is the failure point. Since CCA left most residential use, the replacements — ACQ, copper azole, ACZA — corrode zinc and plain steel markedly faster, because copper drives a galvanic cell against the fastener wherever there is moisture. The answer is hot-dip galvanizing to ASTM A153, and Type 304 or 316 stainless for severe exposures. Every fastener in one joint must share the same metallic composition. Not cosmetic: the stringer-to-pile-cap connection is the load path.
What actually takes small bridges out.
Not the deck, and rarely the load. The water goes after the foundation.
The references are the FHWA circulars — HEC-18 on scour at bridges, HEC-23 on countermeasures. In plain terms: set the top of the foundation below the combined depth of contraction scour and long-term channel degradation, then protect the abutment against local scour with rock. You build for the bed the creek will have in thirty years.
Debris loading is a design case, not an accident — a flood on a piney-woods creek arrives as a raft of timber, and a pier that is fine in clear water is a dam once the raft catches. Lateral migration, the creek walking sideways over years, is answered by where you build, not a heavier deck.
Driven piles taken below the anticipated scour depth are ordinary work here. A crossing on shallow footings has no answer to scour, and finds that out once.
What to ask, and who to ask.
Every determination below is made by an agency, never by a contractor.
The federal trigger is fill, not the bridge. Section 404 of the Clean Water Act regulates discharging dredged or fill material into waters of the United States, so it is the piers, riprap, pipe and approach fill that draw review. A driveway or ranch-road crossing is commonly routed through Nationwide Permit 14, which covers linear transportation projects and names driveways. It carries acreage limits and runs in five-year cycles, so check the current version.
Clear span changes the arithmetic. A single span on abutments set outside the channel places no fill below the ordinary high water mark, so where a crossing can be clear-spanned the burden can be lighter than the culverted crossing you were about to build instead — the opposite of what most owners assume. Approach fills are regulated separately, and jurisdiction is the Corps district's call.
Then two Texas layers. TCEQ reviews Section 401 certification on projects needing an individual 404 permit, and runs a tiered system: for a Tier I project — under 1,500 linear feet of stream or under three acres of waters in the state, and clear of rare wetlands and coastal critical areas — submitting a signed Tier I best-management-practices checklist with the application means no further 401 review. Most ranch crossings fall inside those thresholds. Nationwide permits carry their own 401 certification, which is a separate route. And under the Texas Natural Resources Code a navigable stream is one that keeps an average width of thirty feet from its mouth up. Texas courts have read that width across the whole bed, including the parts dry on any given day — so a creek dry most of the year can still be statutorily navigable, and on one of those the State's interest runs below the gradient boundary. Whether yours qualifies is a determination, not a measurement you make yourself.
The one that catches people is local. A Floodplain Development Permit from the county floodplain administrator is required before construction in or adjacent to the 100-year floodplain, and the application comes from the property owner or their legal representative rather than from the contractor. In a floodway it must be shown not to raise the base flood elevation. Dave builds the structure; a licensed engineer stamps the hydraulics.
A crossing, from the abutment out.
The deck is the part people see. What decides whether it is still there in twenty years is the timber going into the bank at either end.
Not every crossing is a bridge.
A short span over a creek is often better solved with a decked crossing on steel wingwalls than with a full bridge. It costs less, it holds the banks either side, and it does not need a span to carry.
Timber bridge FAQ.
Do I need a bridge, or would a low-water crossing do?
Often a low-water crossing is the right answer, and we will say so. On a draw that runs hard a few days a year, a properly built crossing is cheaper and does the job. A bridge earns its cost where it is the only way in and out, staying usable during the high water.
How far can a timber bridge span?
Solid sawn timber stringers generally run out somewhere around 26 feet. Past that the options are glulam, or an intermediate pile bent that turns one long span into two. Most Texas creek crossings are wider than 26 feet, so the usual answer here is a multi-span, pile-supported bridge.
What load should a private bridge be built for?
HS-20 is the common benchmark for a vehicular private bridge: 72,000 pounds on three axles. HL-93 is the modern AASHTO model, pairing a design truck or tandem with a distributed lane load. Capacity is never one number, because axle spacing changes what a span can carry. Tell us the heaviest thing that will ever cross.
Do I need a permit to build a bridge over a creek in Texas?
Usually the question is not the bridge but the fill. Section 404 of the Clean Water Act regulates discharging dredged or fill material into waters of the United States, so piers, riprap and approach fill draw the scrutiny. A driveway crossing is commonly routed through Nationwide Permit 14, and a county floodplain permit catches most rural landowners. Jurisdiction is the Corps district's and the county's.
What sets the price, and what is guaranteed?
The span, the number of pile bents, the load rating, how far equipment has to travel, and what the ground at each abutment turns out to be — none of it knowable over the phone, which is why Dave walks it first. On the guarantee: our guarantee typically runs 2 to 5 years on the large Texas and Louisiana lakes and up to 10 years on private ponds and small lakes, with the terms set out in your agreement for the job.
Related services.
Have a span to cross?
Four things get a useful first answer: how wide the crossing is, the heaviest thing that has to cross it, what the water does in a big rain, and whether anything is there now. Based in Trinity — more than 40 years, over 250 boathouses and 850-plus projects — and Dave travels as far as the project warrants.