Roofing Options for Gabled, Flat & Low Slope Sheds

In a hurry?

The short version

Every SolidBuild roof has one of four pitches. Find yours; the rest of the guide follows from it. Nothing for the roof is in the kit except the boards: underlayment, drip edge and the covering are bought locally.

The words on the wrapper

Glossary

Section 1

Know your roof: the pitch

Roof pitch is how many inches the roof rises for every 12 inches it runs. A 4:12 roof climbs 4 inches over a foot; a ½:12 roof climbs half an inch. Roofing products are all rated in this rise-per-12 form, so it's the number to have in your head when you shop.

Both halves of a gable roof have the same pitch. The "flat" modern roofs are not flat: each has a small fall so water drains toward one edge, ½:12 is a 5-inch drop across a 10-foot roof. Moderna and Solana: ½:12 is the published figure and the one this guide uses throughout; the current production drawings measure a little under it, a Moderna falls 3⅞ in across its 11 ft ½ in roof, about ⅜:12. On these two, treat every ½:12 manufacturer's recommended minimum here as one you are sitting on rather than clearing: the membranes, rated to ¼:12, are the covering with room to spare, and everything else on them carries a condition.

Section 2

Why the pitch decides the roofing

Shingles are small overlapping pieces. They keep water out by gravity: rain hits a shingle, runs down onto the one below, and off the roof. The flatter the roof, the slower the water moves, and wind can push it back up under the overlaps. Below a certain pitch, shingles simply stop working, which is why the building code and every shingle manufacturer set the same limits:

• Under 2:12: no asphalt shingles at all. Water sits, and a shingled roof will leak. This is the whole modern line: Moderna, Solana, Washington, Astoria and California.
• 2:12 up to 4:12: shingles are allowed, but only over "double underlayment": two layers of roofing felt, overlapped so that every spot on the roof is covered twice, or one stick-down ice-and-water membrane over the whole roof instead. That is Gardener, Optima, Bristhol, Aspen and Dakota.
• 4:12 and steeper: standard installation, one layer of underlayment. That's Shiba, Myrtle and Whales. They sit exactly at 4:12, the lowest pitch that still counts as standard, so if the budget allows we'd still use the two-layer method on them.

Membranes (EPDM rubber, TPO/PVC) work the opposite way: one big sheet, glued or welded together, with no overlaps for water to creep back up. They are rated down to ¼:12, which is why they are the answer for the flattest roofs. Metal panels and roll roofing sit in between, each with its own minimum; the table in the next section has all of them.

Section 3

Which roofing fits which shed

Green means the covering is rated for the pitch. Amber means it works with a condition, read the note. Red means the product's own minimum is steeper than the roof: don't.

Minimums from the International Residential Code (R905) and the manufacturers' installation instructions (sources in section 12). Where a manufacturer is stricter than the code, its condition is written into the cell, you are buying their product and their warranty.

Section 4

What it costs, model by model

Guide figures at our calculator's 2026 rates: roof area plus a 10 % waste allowance, times the material rate. The "usual choice" is shingles on the gable models and EPDM on the modern ones. The underlayment column is the extra for the two-layer method under shingles, a second layer of felt at about $0.15/sq ft, or an ice-and-water membrane at about $0.60/sq ft (budget rolls; premium brands about double); it applies on the 3:12 models and is optional on the 4:12 ones. Drip edge is $1.50 a foot around the roof. Roofing nails, adhesive, primer and tools are on top.

Shingles at the calculator's "Felt Paper + Asphalt Shingles" rate of $2.20/sq ft (one felt layer implied), EPDM at its $2.50/sq ft rate, all-in guide rates; the calculator does not itemise nails or adhesive. For any other combination, metal, cedar, clear panels, insulation, labour hours, use the project cost calculator, which prices every option on your model's own roof area.

Section 5

The coverings, one by one

Guide prices are the per-square-foot rates the calculator uses (material, 2026). Lifespans are typical for the material; the manufacturer's warranty is the number that counts.

Asphalt shingles

The familiar choice, and the easiest to match to the house. They come in bundles, usually three bundles to 100 sq ft, the bundle tells you what it covers. They nail down over an underlayment. Three-tab shingles are cheapest; architectural (laminated) shingles are thicker and last longer. On the 3:12 models there's one rule that really matters: two layers of felt underneath, or an ice-and-water membrane (section 6). On the 4:12 models one layer is all the code asks for, we'd still use two, but that's our advice, not a rule.

About the nails. The code and the shingle manufacturers all want the nail to bite at least ¾ in into the roof boards, or go right through them. Our roof boards are ¾ in tongue-and-groove spruce (if another page tells you ⅝ in, just measure a board). For three-tab shingles, 1 in nails are what you need. Architectural shingles are thicker, so do the math before you buy: two layers of shingle, since every nail goes through the overlap, plus the ¾ in of the boards. If that adds up to less than your nail is long, the point comes out the other side, lay a sheet of OSB or plywood over the boards first and nail into that with 1¼ in roofing nails. The only downside is the added weight, which comes out of your snow-load allowance.

Fits

4:12 and 3:12 models

Minimum

2:12; two layers under 4:12

Guide price

$2.20 / sq ft (calculator rate, felt + shingles)

Lifespan

20–30 years

DIY

Easy; a day for two people

Roll roofing and self-adhered 2-ply systems

Roll roofing is shingle material in a roll. The ordinary mineral-surfaced roll (GAF Mineral Guard and the like) nails down with each strip overlapping the one below. The code allows roll roofing from 1:12, but this common product says 2:12 on its wrapper, so on the 1:12 models buy a roll whose label says 1:12, or use the double-coverage method: 36-in strips with only 17 in showing, every overlap glued with roofing cement, and the nails hidden under the next strip. Suppliers call this the concealed-nail method.

The modern version is a self-adhered two-ply system, a base sheet and a granulated cap sheet that stick down without a torch (GAF Liberty, CertainTeed Flintlastic SA). GAF rates Liberty from ½:12 and wants it on primed plywood, so over our plank boards you'll first put down a nailed base sheet or a sheet of plywood or OSB, primed the way the kit tells you. Set the end overlaps in a bed of the manufacturer's cement, press every overlap down with a weighted roller, and on anything steeper than 1:12 (that's the gable models) nail the top edge of each cap sheet before the next one covers it. Work between 45 and 95 °F. It's a good budget choice on the 1:12 models; on Moderna and Solana you're right at Liberty's recommended minimum of ½:12.

Fits

roll: 4:12, 3:12, 1:12 (rated roll) · 2-ply: every model, over plywood or a base sheet

Minimum

1:12 roll · ½:12 two-ply

Guide price

$1.90 / sq ft (2-ply)

Lifespan

about 20 years

DIY

Easy to moderate

MFM Peel & Seal

A self-adhesive aluminium-faced membrane in rolls: peel the backing off, stick it down, overlap 3 in along the sides and 6 in at the ends, then roll it down hard. It's reflective, so it keeps the shed cooler in strong sun. MFM says never to stick it straight onto tongue-and-groove plank boards, and it will not warrant it on boards that still hold tree resin, which is exactly the kit roof. On a SolidBuild shed it goes over a sheet of plywood or OSB laid on the boards and primed with MFM's primer (or over a nailed, primed base sheet). Minimum slope ½:12, no puddles left standing, and don't walk on it once it's down. Boards and air both above 55 °F when you lay it. It won't let moisture through (it's a vapour barrier), so keep the roof ventilated.

Fits

every model, over plywood/OSB

Minimum

½:12

Guide price

$2.00 / sq ft

Lifespan

10-year warranty

DIY

Easy

EPDM rubber and TPO / PVC membranes

One big sheet of rubber (EPDM, black) or plastic (TPO or PVC, usually white and reflective), glued down with the manufacturer's adhesive, the edges finished with trim or a termination bar, the metal strip that clamps the edge down. Rated to ¼:12, so this is the covering made for Moderna and Solana, and a fine choice on Astoria, California and Washington. EPDM stays flexible in hard frost and copes with roof heat; our FAQ calls it the most popular DIY choice for flat roofs.

Buy the sheet by the roof's two sides, not by its area, and add 12 in overall to each dimension, about 6 in of spare at each edge to fold down and trim, rounded up to the next half foot. The common 10 × 20 ft DIY sheet is 200 sq ft but only 10 ft wide, and every SolidBuild modern roof is wider than that: buy a wider sheet from a roofing supplier, or plan one seam joined with the manufacturer's seam tape.

Model	Roof size (our records)	Sheet, at least (roof + 12 in on each dimension)
Moderna	11 ft ½ in × 11 ft ½ in	12½ × 12½ ft
Solana	14 ft 1 in × 10 ft 6 in	15½ × 12 ft
California	12 ft 10½ in × 12 ft 10½ in	14 × 14 ft
Astoria	11 ft 9 in × 15 ft 9 in	13 × 17 ft
Washington	17 ft 5 in × 16 ft 4 in	18½ × 17½ ft

Fits

Every model

Minimum

¼:12

Guide price

$2.50 / sq ft (calculator rate; September 2026 retail: a 10 × 20 ft sheet $190, a gallon of adhesive $47)

Lifespan

20–30 years

DIY

Easy to moderate

Metal panels, screw-down

Corrugated or ribbed steel panels, screwed down through the face with rubber-washered screws, each panel overlapping the next by one rib. They last a long time and come in plenty of colours. The rubber washers under the screws are the part that ages, so look them over every couple of years and replace any that have cracked. Panels simply overlapped need 3:12 by code, so any panel suits the gable models. Below that the code allows ½:12 as long as you seal the overlaps, and each panel manufacturer sets its own recommended minimum: Metal Sales rates its R-panel and PBR profiles to 1:12 with sealing tape (butyl tape) in the side overlaps and short screws through them (stitch screws), while its Classic Rib, the thin panel sold by the sheet at hardware stores, is rated 3:12. So on Astoria, California and Washington, buy a panel whose label says 1:12, seal every side overlap and screw through it. Customers have used screw-down metal on Moderna and Solana too and it has worked, with every overlap sealed and screwed. Just go in knowing those two are below the 1:12 the manufacturers recommend, so the washers matter more here than anywhere: check them every couple of years and replace the cracked ones.

Fits

4:12 and 3:12: any panel · 1:12: a 1:12-rated panel with the overlaps sealed · ½:12: overlaps sealed and the washers checked every couple of years

Minimum

3:12 plain · ½:12 sealed (code) · 1:12 by panel manufacturer

Guide price

$1.80 / sq ft

Lifespan

20–60 years

DIY

Moderate

Metal, standing seam

Panels joined by raised seams with no screws showing, the premium metal roof, often quoted at 80 years. Some clip-together panels are rated to 1:12 over a solid surface (Metal Sales Vertical Seam); others need 3:12 (MBCI LokSeam), so read the label. The kind that's crimped shut with a seaming tool (mechanically seamed, if you're searching for it) goes down to ½:12, which makes it the standing-seam choice for Moderna and Solana, and a job for a roofer, since that tool is the whole trick.

Fits

4:12, 3:12; 1:12 with a 1:12-rated clip-together panel; ½:12 crimped seam

Minimum

¼:12 code · 1:12 clip-together · ½:12 crimped seam

Guide price

$5.00 / sq ft

Lifespan

about 80 years

DIY

Clip-together yes; crimped seam no

Clear polycarbonate or PVC panels

Corrugated see-through panels that let daylight in. They screw down onto shaped foam fillers (closure strips), with no underlayment underneath, it would block the light. Manufacturers want 1 to 1½ in of rise per foot (Onduline Tuftex 1:12; Palram Suntuf and Palruf 1½:12, and in heavy-snow areas Tuftex asks for up to 3:12), so they suit the gable models and, with a 1:12-rated product, the Astoria, California and Washington. The Bristhol in the photo has several roof boards left out to let more light in. Talk to us before you copy that, those boards are what carry the snow.

Fits

4:12, 3:12; 1:12 with a 1:12 product

Minimum

1:12 to 1½:12 by manufacturer

Guide price

$1.80 / sq ft

Lifespan

varies by product

DIY

Easy

Section 6

Underlayment: the layer nobody sees

Underlayment is the roll of felt (or synthetic sheet) that goes between the roof boards and the covering. Under shingles you can't skip it, and on a 3:12 roof it's the layer that keeps you dry. The code gives you two ways to do it:

Option 1: two layers of felt

Start with a 19-in-wide strip along the eave, then lay full 36-in sheets so each one covers the top 19 in of the one below (17 in shows; make it 20 in if your shingle wrapper says so). Overlap 4 in at the ends and stagger those joints. #15 felt is fine under the model code, though some towns don't allow it and #30 is thicker and tears less. Even overlapped like this, a 432 sq ft roll of #15 still covers about 204 sq ft, so one roll does both layers on every model except Dakota (with 20-in overlaps, a Bristhol needs a second roll). With #30, which comes in 216 sq ft rolls, plan one extra roll on every model except the Shiba. Priced by the square foot, the way the calculator does it, the second layer is about $13 on a Shiba and $29 on a Bristhol; bought as whole rolls it is usually nothing extra with #15 and one more $35 roll with #30.

Option 2: ice-and-water membrane over the whole roof

A stick-down rubberised sheet (Owens Corning WeatherLock, GAF WeatherWatch or StormGuard, Grace Ice & Water Shield, Henry Blueskin and others, look for ASTM D1970 on the label). Peel the backing, stick it down, overlap 3 in, no nails. It seals itself around the shingle nails, which is why several manufacturers recommend it (CertainTeed requires it wherever snow or ice occur; IKO and Atlas recommend it; the others accept either option) and why we do. A 200 sq ft roll covers about 183 sq ft once you allow for the overlaps: one roll for Shiba, Gardener, Aspen, Myrtle and Whales; two to be safe on Optima and Bristhol (one roll covers their bare roof but not the 10 % waste margin); always two on Dakota. Expect about $77–116 a roll for the cheaper ones (Home Depot, September 2026) and about $186–293 for the big-name brands. This is the option we recommend if the extra $50–120 fits your budget (about $165 on a Dakota). One $110 roll covers every model except Optima, Bristhol and Dakota, and you won't need the $35 roll of felt.

Drip edge

An L-shaped metal strip along the roof edges that throws water clear of the boards instead of letting it run back behind the fascia. It's cheap, about $1.50 a foot around the roof, so $48–90 for a shed, and the code requires it under shingles. Along the eaves it goes under the underlayment; along the rakes it goes over it. Nail it every 8–12 in, overlap the joints 2 in, and let the lip hang at least ¼ in below the boards with the flat leg sitting 2 in onto the roof. It also changes when you fit the fascia boards, see section 9.

Section 7

How to shingle a gable shed (4:12 and 3:12 models)

What you'll need: shingles for the roof area plus 10 % (the calculator does this for you), starter strip (or cut shingles), ridge caps, underlayment (two layers or an ice-and-water roll on the 3:12 models; one layer, or the same, on the 4:12 models), drip edge for the perimeter, roofing nails (1 in for three-tab on the bare boards; for architectural shingles measure two layers of shingle plus the ¾ in boards against the nail length, and add an OSB or plywood layer with 1¼ in nails if the nail is longer), a utility knife with hook blades, a chalk line, a tape measure, a hammer or a roofing nailer, and a ladder that reaches past the eave. Two people and one dry day.

Section 8

How to roof a flat or low-slope shed (1:12 and ½:12 models)

EPDM membrane: the usual choice

What you'll need: one EPDM sheet at least 12 in longer and 12 in wider than the roof (section 5 lists every model's roof size; a Moderna needs 12½ × 12½ ft, and a 10-ft-wide sheet is too narrow for any modern model), the manufacturer's bonding adhesive, a paint roller and a stiff broom, edge trim or a termination bar plus the fascia boards, a sharp knife, and a dry, still day within the temperature range printed on the adhesive can (most want 40 °F and rising). One or two people, half a day. The safety tip above applies here too.

If you'd rather not use EPDM

• Self-adhered 2-ply (every modern model): a nailed base sheet, or a sheet of plywood or OSB primed over the boards. Start the base sheet at the low edge, overlap the sides on the printed line (at least 4 in) and the ends by 6 in, staggering those joints. The cap sheet goes on the same way, with its end overlaps set in a bed of the manufacturer's cement. Press every overlap with a weighted roller and work between 45 and 95 °F. On these gentle slopes you don't need to nail the top edges.
• Peel & Seal (every modern model): over a primed plywood or OSB layer, never straight onto the boards; overlap 3 in along the sides and 6 in at the ends, roll it down hard, and work above 55 °F. Nobody walks on it afterwards.
• Roll roofing (Astoria, California, Washington): a roll whose label says 1:12, or the double-coverage ("concealed-nail") method with the nails hidden and every overlap glued; one layer of underlayment first.
• Screw-down metal: on Astoria, California and Washington an R-panel / PBR-type panel rated 1:12; on Moderna and Solana it has worked for customers with the same care and the gaskets watched. One layer of underlayment. Cut the panels to run from the low edge to the high edge in one piece, start at the end away from the prevailing wind and work across, put sealing tape (butyl tape) in every side overlap with short screws through it (stitch screws), drive the rubber-washered screws where the panel manufacturer's instructions show them, and fit the foam fillers (closure strips) at both ends.
• Standing seam: a clip-together panel rated 1:12 over the solid boards on Astoria, California and Washington; on Moderna and Solana only the crimped-seam kind (rated ½:12), which is a contractor's job.
• Clear panels (Astoria, California, Washington): a product rated 1:12, sitting on the foam fillers (closure strips), with no underlayment.

Section 9

Fascia boards and drip edge: before or after the roofing?

The kit's fascia boards can go on before or after the roofing, the manual leaves that to you. Here are its tips and what they mean in practice:

• Want the fascia to hide the edge of the roofing, and no drip edge? Roof first, then fit the front and back fascia so their top edge sits just above the covering. That's the manual's tip.
• Using drip edge? The manual suggests skipping the decorative diamond on the gable models, or fitting it last, so the drip edge isn't in its way. We'd fit the front and back fascia first so the drip edge can lie over their top edge, then do the roofing.
• Wrapping the felt over the edge of the roof boards? Add the felt first, then put the roof end boards over the wrapped edge to hold it down. That one's from the manual too.

Section 10

Insulating the roof

If you're going to heat or cool the shed, the roof gets insulated above the kit boards, so you keep the tongue-and-groove ceiling on show inside. Two things carry over from the rest of this guide: the underlayment still follows whatever covering you chose, exactly as on an uninsulated roof, and everything you add on top of the boards, lumber, OSB, a second layer of felt, a heavy covering, is weight that comes straight out of the snow-load allowance on your model's spec card. Our insulation guide has the full method; the layers, from the inside out:

Section 11

Common customer questions

Section 12

Where these rules come from

• International Residential Code 2021 and 2024, chapter 9: R905.2.2 (asphalt shingles, 2:12 minimum; double underlayment from 2:12 up to 4:12), Table R905.1.1(2) and R905.1.1 Exception 1 (the overlap method and the stick-down alternative), R905.1.2 (ice barrier), R905.2.5 (nail penetration), R905.2.8.5 (drip edge at eaves and rakes), R905.5.2 (roll roofing 1:12), R905.7.2 (wood shingles 3:12), R905.10.2 (metal panels: 3:12 plain, ½:12 with the overlaps sealed, ¼:12 standing seam), R905.11–R905.13 in the 2021 edition (modified bitumen and single-ply membranes, ¼:12; R905.11–R905.12 in 2024), R105.2 (sheds up to 200 sq ft exempt from a permit, not from the code).
• Installation instructions of GAF, Owens Corning, CertainTeed, IKO, Malarkey, TAMKO and Atlas, and the warranties of GAF, Owens Corning, CertainTeed, IKO, Malarkey and TAMKO (asphalt shingles); the Cedar Shake & Shingle Bureau roof manual (cedar); GAF Liberty and CertainTeed Flintlastic SA (2-ply); MFM Peel & Seal application instructions; Metal Sales and MBCI (metal panels); Palram Suntuf/Palruf and Onduline Tuftex (clear panels); the EPDM Roofing Association; ARMA (double-coverage roll roofing).
• SolidBuild assembly manuals (fascia, drip-edge and felt-wrap tips), the SolidBuild insulation guide and FAQ, fifteen years of customer roofs, and our project cost calculator's 2026 rates. Underlayment and membrane prices: Home Depot and Menards, September 2026.

This guide is general information for owner-builders. Roofing products change, so the instructions printed on the product you buy, and your local building department, always come before anything here. If something in it doesn't match what you have in front of you, get in touch and we'll work it out with you.