What Is a Firewood Shed Roof Overhang? (Rain Runoff Spacing)
A firewood-shed roof overhang is the part of the roof that extends past the shed wall. It carries rainwater beyond the wall and, when sized and placed well, beyond the wood stack. A useful starting point is 12–18 inches of projection, with at least 12 inches between the stack’s outer edge and the roof’s drip line.
If you are planning a shed or checking one you already have, the key question is simple: where will the rain fall? A deep-looking eave can still leave wood wet if the stack sits too close to its edge or wind blows rain under the roof.
I explain overhangs by finding the roof’s drip line first, then comparing it with the planned stack and the ground below. That approach makes the measurements easier to understand and helps avoid relying on the overhang alone to keep wood dry.
Overhang Layout, Roof Design & Safety Preparation
A roof overhang, also called an eave projection, is the distance the roof extends horizontally past the wall. It gives runoff a path away from the wall and wood. Its size must suit the stack location, weather exposure, roof covering, and the framing that supports it.
For many firewood sheds, start with a projection of 12–18 inches (300–450 mm) beyond the wall. On a side exposed to wind-driven rain, 18–24 inches (450–600 mm) may be worth considering, but only if the framing can safely support it.
These figures are starting points, not a guarantee that wood will stay dry. Local snow and wind loads, roof design, and the shed’s location all affect what is suitable. If the framing capacity or local requirements are unclear, get a suitable structural detail before extending the roof.
Check the site and roof before choosing a projection
Before deciding how far the roof should extend, look at the site. Note which direction storms usually come from, whether water has a clear route away from the shed, and whether the ground slopes toward or away from it. Check local requirements for snow and wind loads as well.
The roof covering also matters. Follow its manufacturer’s instructions for minimum roof pitch and installation. For common asphalt shingles, a pitch of at least 2:12 may be used only where the manufacturer permits it and the required low-slope underlayment is installed. Do not assume that pitch suits other roof coverings.
An overhang also needs proper support. Rafters, lookouts, fascia, and their connections must suit the proposed projection and local loads. A larger projection can catch more wind and add demands to the framing. Do not extend an unsupported eave based only on a general measurement.
Work out the roof-edge position
Measure from the wall to the planned outer face of the wood stack. Call this distance D. Then use this starting rule:
Roof projection P ≥ D + 12 inches (300 mm).
This places the roof’s drip line at least 12 inches beyond the stack’s outer edge in calm, straight-down rain. For example, if the wood’s outer face will be 10 inches from the wall, the roof projection should be at least 22 inches to provide that clearance.
This calculation does not account for rain blowing sideways. At exposed sites, increase the stack setback, consider a longer supported overhang, or do both. The roof edge is also not the only factor: flashing, drip edge, roof covering, and installation all affect how water leaves the roof.
Runoff Clearance and Firewood-Stack Placement
The roof drip line is the line where water leaves the roof edge during ordinary rainfall. Keep the nearest firewood at least 12 inches inside that line, so runoff falls beyond the stack. More clearance may be needed where wind pushes rain beneath the eave or water splashes back from the ground.
Think of the stack’s outer face as the point that matters most for this check. Measure from the shed wall to that face, then compare it with the roof projection. The drip line should fall at least 12 inches farther out than the stack’s outer edge.
| Site or stack situation | Starting projection or clearance | What to check |
|---|---|---|
| Sheltered side, stack close to wall | 12–18 in. beyond wall | Keep the drip line at least 12 in. beyond the stack |
| Stack outer face 10 in. from wall | At least 22 in. projection | Confirm the framing supports the projection |
| Exposed side with wind-driven rain | Consider 18–24 in. beyond wall | Increase setback or projection as conditions require |
| Ground below roof edge stays wet | Projection alone is not enough | Improve drainage and prevent ponding |
The table gives planning starting points, not a substitute for structural design or site checks. If the stack is moved, recalculate the needed projection. A roof edge that clears today’s stack may no longer clear it after the pile grows.
Keep the drip zone and ground in mind
Even when runoff clears the wood, water may splash off hard ground and reach the lower rows. Where possible, keep the drip zone from becoming a wet strip beside the shed. Avoid placing posts or foundations where runoff will pond against them.
As a general drainage target, grade the ground away from the shed at about 2%, or roughly ¼ inch per foot, for the first 5–10 feet. If the site cannot be graded this way, provide equivalent drainage. The aim is to move water away, not trap it beside the shed.
Do not treat the overhang as a fix for poor ground drainage. A long eave may move the drip line outward, but it will not stop water from collecting at the shed or splashing onto the wood.
Worked layout scenarios
These examples show how the sizing rule works. They are planning scenarios, not reports of specific installations.
- Sheltered site: The stack’s outer face is 4 inches from the wall. The formula gives a minimum projection of 16 inches: 4 inches plus 12 inches of clearance. A 16-inch projection meets the basic drip-line target, though the selected roof design and local loads still need checking.
- Stack set farther out: The outer face is 10 inches from the wall. A projection of at least 22 inches is needed for 12 inches of clearance. If that projection is not suitable for the framing, move the stack closer to the wall or get a designed support detail.
- Wind-exposed side: The stack’s outer face is 10 inches from the wall, but storms often drive rain toward that side. The 22-inch calculation is only a baseline. More setback, a longer supported overhang, or both may help, but wind can still carry rain beneath the roof.
These examples highlight a useful choice: sometimes moving the stack is simpler than extending the roof. Whatever you change, check the new drip line against the stack and the ground.
Inspection, Drainage Checks & Repairs
A runoff check confirms whether roof water leaves the wall and stack area as intended. Inspect the roof edge, stack position, and ground together. During rain, look for water tracking back under the roof edge, wet outer rows, or pooling near posts and the shed base.
Use this sequence when planning or reviewing the layout:
- Check the site and loads. Identify the usual storm direction, the ground slope, a drainage outlet, and local snow and wind requirements. Confirm that the proposed projection is supported by suitable rafters, lookouts, fascia, and connections.
- Mark the stack line. Decide how deep the stack may be, then mark its maximum outer face. Measure from the wall to that mark and add at least 12 inches for the basic projection target.
- Build and cover the roof correctly. Use framing and fasteners suited to the design and loads. Install the selected roof covering, flashing, and drip edge according to their manufacturer instructions.
- Check runoff in rain. Confirm that water falls outside the stack footprint, does not run back under the edge, and drains away without ponding. If it does not, adjust the stack position or drainage, or review the roof detail.
If water tracks back under the edge, inspect the roof covering, flashing, and drip-edge installation rather than assuming that a longer overhang will solve it. If the ground ponds, address drainage. If the framing appears unsupported or has shifted, do not add more roof projection without an appropriate structural detail.
A simple measurement can catch many layout problems: mark the drip line on the ground, then compare it with the stack’s outer edge. Keep the wood at least 12 inches inside that line, and increase the margin if rain is driven beneath the eave.
Seasonal Care and Weather Readiness
Seasonal checks help confirm that the roof still sheds water clear of the wood and that the ground remains free-draining. Recheck after moving or enlarging the stack, after roof repairs, and when you notice wet wood or standing water near the shed.
Wind-driven rain is the key edge case. Even a deep overhang may not keep the outer rows dry if wind blows rain beneath it. In that situation, increase the stack setback or consider a larger, properly supported projection. Positioning the more sheltered side toward the prevailing storm direction may also help where the site allows it.
Keep the shed open enough for airflow. Closing it tightly to block rain can interfere with firewood drying. The goal is to protect the stack from direct runoff while preserving ventilation, not to seal the shed like an indoor room.
Before wet or snowy weather, look for changes that affect runoff:
- Check whether the roof edge, flashing, or drip edge is loose or damaged.
- Confirm the stack has not grown past its marked line.
- Look for soil or debris that blocks the path of water away from the shed.
- Check for ponding near posts, the foundation, or the wood.
The key measure is still the same: the drip line should land at least 12 inches beyond the stack, and runoff should drain away from the shed.
Frequently Asked Questions
These answers cover the main planning questions: what an overhang does, how to measure it, and what can make a basic clearance insufficient. The measurements are starting points. Roof covering instructions, structural capacity, local loads, and site drainage still govern the final design.
How far should a firewood-shed roof overhang extend?
Start with 12–18 inches beyond the wall. Consider 18–24 inches on an exposed side, but only when the framing can support it.
How much clearance should there be between firewood and the drip line?
Keep the stack’s outer edge at least 12 inches inside the roof drip line. Increase that gap where wind-driven rain or splashback is a concern.
How do I calculate the projection I need?
Measure from the wall to the stack’s outer face, then add at least 12 inches. For example, a stack face 10 inches from the wall calls for at least 22 inches of projection.
Can a long overhang keep all rain off firewood?
No. Wind can blow rain beneath the eave, and water can splash up from the ground. More setback or projection may help, but check drainage and keep the shed ventilated.
Is a 12-inch overhang enough?
It can be a starting point when the stack is near the wall and the site is sheltered. Check that the drip line still lands at least 12 inches beyond the stack.
Does a larger overhang need extra support?
It may. Rafters, lookouts, fascia, and connections must suit the projection and local wind and snow loads. Get a suitable structural detail if capacity is uncertain.
What roof pitch should a firewood shed have?
Follow the roof-covering manufacturer’s minimum pitch. Common asphalt shingles may be used at 2:12 or steeper only where the manufacturer permits it and required low-slope underlayment is installed.
How should the ground slope around the shed?
A general target is about 2%, or ¼ inch per foot, away from the shed for the first 5–10 feet. Provide equivalent drainage if that grade is not practical, and avoid ponding at posts or the foundation.
(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)
