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By Amy Hanlon on 28 Sep 2023

What’s the best roofing material for a timber garage?

You don’t have to know the best roofing material for a timber garage. But if you do, you’re more likely to buy a building that stays dry, solid and sturdy for many years.

So let us help. We’ll use our decades of experience with timber buildings to run through your options so you can identify the best choice.

Is a timber garage just a big shed?

A small apex Gillies & Mackay shed painted cream. It has a door and a window and steel box profile roofing.

Most timber garages on the market are in fact big sheds. They’re constructed in the same way as a shed.

In fact, this is how we used to build our garages. Since we build great sheds, we figured we’d build great garages. But we were actually building big single-skinned sheds.

What is a single-skinned building?

Single-skinned buildings have only one layer of timber cladding forming their walls. This description applies to most sheds and summerhouses. Most timber garages are single-skinned. Depending on the manufacturer, this cladding skin may be as thin as 5mm or as thick as 22mm. Timber garages built with a single layer of timber cladding usually use thicker cladding.

Why shouldn’t I keep my car in a timber shed?

A pent timber garage by Gillies & Mackay with a classic Ford Capri and a Chopper bicycle visible inside.

However, we found that this approach wasn’t enough to keep out the pouring rain, sleet and snow that we get in this part of the world. Scottish garages need more than a single skin of timber to keep water out.

When water gets into a garage it can damage both the building and the contents of the building. If you’ve built a garage to keep your precious classic car safe from the elements, the last thing you need is a leak!

Are timber garages watertight?

A diagram of Gillies & Mackay's timber garage specification, showing the layered walls.

If a timber garage is going to be watertight, it needs layered walls. A single layer of timber cladding will likely let in some water.

But timber cladding with an air gap behind it, then a damp-proof membrane and an insulating layer of OSB will stay dry no matter what the weather does.

So that’s how we build our garages. Accept nothing less. If it doesn’t have layered walls, it’s not a garage; it’s a big shed.

What roofing options are there for timber garages?

When you’re looking to build a watertight building, your choice of roofing material is crucial.

There are three main options for timber garage roof materials. Both sloping pent garages and pointed apex garages generally use roofing felt, shingles, or metal roofing. What are the pros and cons of these options?

What is roofing felt?

A small Gillies & Mackay garden shed painted pale green. It has a door and two windows and sits on a concrete slab base. It has a bitumen felt roof.

Roofing felt consists of polyester or fibreglass sheets coated in bitumen. It comes in a variety of thicknesses and qualities. Roofing felt is fixed to your garage roof using adhesive, roofing tacks, or a heating torch which bonds the felt to the roof underneath.

What are the advantages of roofing felt on a timber garage?

Roofing felt is a cost-effective roofing solution. It is easily installed – with the exception of torch-on felt – and if your goal is to keep costs down it’s a reasonable choice. It is fairly weather resistant and the bitumen sheets are available in various sizes and qualities, with a range of prices.

Pros: roofing felt is affordable and relatively easy to install.

What are the disadvantages of roofing felt on a timber garage?

However, it is not suitable for buildings with a flat roof or pent roof. If water pools and sits on your garage roof, over time the felt will wear away and it won’t withstand extreme weather conditions. Since we live in Scotland, extreme weather conditions come around every few weeks.

Felt isn’t the best choice for larger buildings like garages. Since felt roofing sheets usually come in rolls that are smaller than a garage roof, joins are necessary between the strips. These joins are particularly susceptible to water ingress.

Cons: Felt has a life expectancy of 10-15 years, and can fail if exposed to too much water. It’s not suitable for flat or gently sloping roofs.

What are shingles?

Closeup of a Gillies & Mackay shaped summerhouse with a shingled roof.

Shingles are small, shaped mats made of rubber, bitumen, metal or wood. They are installed by fixing them to a garage roof in an overlapping pattern.

What are the advantages of shingles?

A closeup of a roof with threem small balconies. The roof has been clad with zinc shingles and curves oddly around the balconies.

The overlapped structure of a shingle roof makes it extremely resistant to water ingress. Shingles come in all sorts of materials, colours, shapes and patterns, so they provide plenty of customisation options.

Western red cedar was the traditional material for roof shingles. This option is still available but sourcing this timber can be tricky, especially if you’re interested in ethical timber. Other materials include bitumen, recycled plastic, metal and rubber.

The durability and aesthetic appeal of shingles make them a popular choice. They have a life span of 20+ years, depending on quality. Because single shingles can be replaced, maintenance doesn’t have to be a back-breaking affair.

Pros: Shingles are an attractive choice, with a wide variety of options for materials, shape and configuration. They’re long-lasting and easy to replace if any damage occurs.

What are the disadvantages of shingles?

Shingles aren’t suitable for a flat roof but work well on pent garages and any garage roof with at least a 10° slope.

Cons: Shingles are the most expensive of these three options. The skill and labour required for installation are greater than any other roofing material. Both this and the outlay for the shingles themselves will add to the cost of your garage project.

What is steel box profile garage roofing?

A closeup of a Gillies & Mackay shed roof, showing the steel box profile roofing sheet.

It’s no secret that we love steel box profile roofs around here. Steel box profile roofs consist of shaped sheets of galvanised steel. We use this roofing material on all of our sheds and the vast majority of summerhouses, garages and garden rooms. Why are we such fans?

What are the advantages of steel garage roofs?

A large timber Gillies & Mackay garage. The garage is stained dark brown and has a grey steel box profile roof.

If you’re looking for low-maintenance durability, go for steel. Some steel roofing sheets have material warranties of 40 years! If you install steel box profile sheets properly they’ll last a lifetime.

High-quality steel garage roofing sheets are plastic-coated, so they’re incredibly weatherproof. The galvanised metal is highly resistant to rust, so once a steel roof has been installed on your garage, it shouldn’t need any repairs or maintenance.

Pros: Durable, weatherproof and reliable – steel is an excellent choice for a long-lasting, low-maintenance garage roof.

What are the disadvantages of steel garage roofs?

Steel box profile roofing costs more than felt, but generally less than shingles. It’s trickier than felt to install but requires less expertise and labour time than roof shingles

While steel roofing isn’t to everyone’s aesthetic taste, it’s a long-lasting, highly reliable roofing material.

Cons: Steel roofing isn’t the prettiest option out there. If aesthetic appeal is top of your list of priorities, it may not be for you.

What other roofing options are there for a timber garage?

Clay tiles and slate garage roofing are available, but these choices need a seriously strong garage underneath to hold their weight. Your garage will need engineered trusses to support slates or clay tiles. This is particularly important if your garage is single-skinned, and effectively a really big shed. Make sure that the specifications of your building can support the roofing material you choose! Another point to consider is that you’ll need a specialist roofer to install and maintain a clay or slate roof. This adds to the cost of these roofing materials, which are already expensive options.

If you’re looking for the appearance of slate without the expense of maintenance, Eco Slate offers the best of both. Made from recycled plastic and fully recyclable, these slates are easier to install than traditional slate and are guaranteed for 50 years. They’re tested to resist winds of up to 50mph and form a waterproof roof that’s not going anywhere.

Which roofing material should I choose?

Ultimately, your choice of roofing material for your timber garage will depend on your budget, your wants and needs and your personal preference.

While roofing felt is a reasonable choice for smaller sheds, it won’t keep a garage dry in the long term.

And don’t forget that big sheds won’t stay watertight either.

Whether you opt for steel or Eco Slate, a Gillies & Mackay Garage will stay solid and watertight for decades to come.

Pop in and see us at our Show Area here in Errol, where you can see one of our gorgeous garages on display. You can also check out the different roofing materials we use.

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