How To Install Roofing Paper
- Written by Justin Stewart on Aug 05, 2009To ensure our content is always up-to-date with current information, best practices, and professional advice, articles are routinely reviewed by industry experts with years of hands-on experience.Reviewed by
Installing roofing paper, or felt, is an essential element to construct a waterproof roofing system. It also acts as a layer of insulation and water protection underneath roof shingles. Installation is not particularly tough when following these simple steps that will ensure a successful project.
What Is Roofing Paper or Felt?
The black rolls of roof paper or felt are made with asphalt and are normally available in rolls. The felt provides a layer of additional weather protection between the roofing finishing material and the roof decking. The most common size width for rolls of roofing paper is 36 inches. It is commonly called 15lb paper. Many rolls are pre-striped allowing installers to keep a straight line when applying roll strips to the roof side by side. All drip edges along roof eaves, valley liners and flashing need to be installed before the roof paper layer is laid down. Only a drip edge along the roof rakes is installed after the paper.
Step 1 – Prep the Area
Step 2 – Roll it Out
Start at the bottom edge of the roof and roll the paper roll out toward the peak.
Step 3 – Overhang Paper
Step 4 – Over the Peak
Roll the roof paper up and over the peak.
Step 5 – Secure Ends
Step 6 – Overlap Next Roll
Step 7 – Trim Excess
Why Should You Use Felt Paper On Your Shed Roof
There are a number of reasons for the installation of felt paper on your shed roof.
- It repels water.
- In the event of ice and water damage it will provide back up protection.
- It provides extra protection against the weather.
- It may be required by your building code in your local municipality.
- It will protect your roof decking while working on your roof.
- It will help your shed roof look better. It will provide a more uniform look and prevent that picture frame effect from the edges of the roof panels.
- Felt paper prevents stains from wood resins.
How To Felt A Pent Shed Roof
Installing felt on a pent shed roof also requires similar steps to those given above for a standard garden shed. Use three strips of felt, and then work your way from the bottom of the roof to the top. Ensure you secure the felt all the way around the edges of the roof. Do not fit fascia boards at the back of the shed, as it will hold water.
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How To Install Underlayment
Installing the underlayment properly is important for keeping the roof water tight and effective. The underlayment goes on top of the plywood decking. This waterproof membrane, also called roof felt, is a tar paper product. This tar product is being replaced by synthetic felts. The fabric has asphalt in it to create a moisture barrier to keep rain from penetrating the wood decking. Different geographical areas require different weight or thicknesses but the average is about 15-pound weight.
The installation of the roof felt or underlayment is a 2 person job. They first need to install the drip edge flashing. This bends over the roof and down the edge of the facing board on all the edges of the roof. The drip edge is fastened to the eaves with galvanized nails prior to installing the underlayment.
The underlayment starts on a bottom corner of the roof, tacked in place at the corner. The end is flush with the end of the roof and the bottom edge of the roll is flush with the bottom of the roof deck overlapping the drip edge. Then you roll out about 10 feet of felt and fasten with roofing nails and plastic washer heads or staples. Fasteners need to be installed ever 8 inches or as specified by the supplier. The top portion of the paper is left loose.
The process is somewhat tedious but relatively simple in nature. Installing underlayment is vital to the durability and water tightness of your roof.
Underlayment On Standard Slopes Where Asphalt Roof Shingles Are Installed
As stated in Best Practices Guide to Residential Construction:
On roofs with a slope of 4:12 orgreater, use a single layer of 15 lb. asphalt-saturated felt,starting at the eaves and lapping upper courses over lowerby a minimum of 2 inches. Vertical joints should lap a minimumof 4 inches and be offset by at least 6 feet in successiverows .
Secure each shingle course along seams and edges withenough corrosion-resistant nails to hold it in place untilthe roofing is installed.
In high-wind areas, apply fastenersa maximum of 36 inches on-center along overlaps.
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Is My Roof Suitable For Roof Shingles
Survey your existing roof structure to decide if it requires maintenance or strengthening before installing any shingles. Make a note of your roof construction you will need to have a decked roof fixed to rafters, or supported on a trussed roof structure.
You will need to measure the slope of your roof with a protractor. This will help determine whether you can fix shingles, and any preparation you need to do. See our three options below for more details.
Roof deck
Roofing shingles must be laid on a roof deck fixed in accordance with the relevant British Standards & Codes of Practice. Shingles can be laid over existing roofing felt, but the surface must be flat and in good condition.
Minimum roof slope 12.5 degrees
Minimum deck thickness 12mm
Underlay
Roofing felt underlay must be used on roof slopes below 20 degrees or a 1 in 5 gradient. Its good practice to always use a roofing underlay below shingles. Roofing felt underlay should be laid on the roof with 15cm end overlaps, and fixed by nailing with 10mm large-headed galvanised clout nails at 10cm intervals.
Applying roof shingles
Safety Issues When Laying Roofing Felt
When working on any roof and laying roof felt, you need to keep safety foremost in your mind. Therefore, never step on a felt roof before it has been secured to the decking with nails. The same is true about repairing the roof.
Otherwise, there is a chance that the felt will slip and you will fall off the roof. Also, always take care when using ladders.
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Install Rake Drip Edge
To protect the rake or gable ends from wind-driven moisture, the drip edge is placed over the underlayment to seal it down to the deck. The felt should be trimmed flush with the edge or 1/2 past to wrap the edge when the drip edge is placed.
Cut the extended eaves drip edge flashing between the roof leg and vertical leg at a 45° or 90° angle to the rake edge. Fold the top part of the extended metal down so it is covered by the rake drip edge.
Start at the lower gable edge of the roof deck and work upward. Upper lengths of edge flashing should overlap lower lengths by a minimum of 6. Nail every 8 to 12 and about 1-1/2 in from the outer face of the drip edge.
Nail every 8 to 12 and approximately 1-1/2 in from the outer edge.
The last part of the extended eaves edge flashing is folded back over the rake edge and nailed into place, thus sealing the exposed corner of the drip edge.
How Do You Install Torch
A mat of fiberglass, polyester, or other material is often used as a sturdy core for torch down roofing membranes. Manufacturers also may embed small granules into the top of the membrane to add fire resistance, color options, ultraviolet radiation protection, or other distinctive characteristics.
Beside this, Do you need underlay for torch-on felt?
The torch-on felt solution relies on a three-layer system, which will require two levels of underlay underneath the cap sheet. Anderson Toptorch SBS SB2 Torch-on Underlay is a solid option, with rolls that cover 16m length, 1m width and have a thickness of 1.5mm available for a manageable outlay.
Likewise, Does torch on felt need underlay?
While roofing felt isnt the cheapest, its one of the most effective systems. The torch-on felt solution relies on a three-layer system, which will require two levels of underlay underneath the cap sheet.
Also, What goes under torch down roofing?
A mat of fiberglass, polyester, or other material is often used as a sturdy core for torch down roofing membranes. Manufacturers also may embed small granules into the top of the membrane to add fire resistance, color options, ultraviolet radiation protection, or other distinctive characteristics.
Do you need underlay for felt roof?
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Repairing Shed Roof Felt
It may happen that a small section of your shed roof felt gets damaged before you are due to replace the felt. In such cases, you do not need to replace everything, which is why it is a good idea to keep any scraps of shed felt left over after an installation.
The first thing you should do is check the entire roof to make sure the rest of the felt is in good condition. You should then clean the area around the damaged section to ensure it is free of dirt, grit, and obstructions. Cut a piece of felt to cover the damaged area.
If possible, cut a square or rectangular piece of felt that is 5cm longer on all sides of the damaged area. You do not necessarily need to nail the felt into place. Instead, you can apply adhesive around the damage, and then press the piece of felt into place over it.
Installing Roofing Felt In Six Easy Steps
Felt roofing is a very common material used on flat roofs such as garages, garden sheds and on extensions. Generally, felt underlay roof works by combining two or three layers of material together to make an impenetrable barrier that is then coated with a waterproof finishing material to further protect the felt.
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Install Step And Dormer Flashing
It’s possible to reuse existing step flashing and dormer flashing, but the best way to get a watertight seal is to tear off the siding in those areas and install new flashing. Start by running self-stick underlayment at least 6 in. up onto the walls. This provides an additional barrier if water does get past the flashing. Cover the front wall first and then work your way up the side wall. Overlap the sidewall underlayment around the corner onto the front wall about 1 in. or so.
Install the shingles right up to the front wall. Cut a couple of inches off the vertical portion of the dormer flashing, and run the horizontal portion past the side wall that same distance. Nail the dormer flashing to both the wall and the shingles.
Make a 1- to 2-in. cut with a tin snips at the bend in the first step flashing. Run a bead of sealant on the corner edge of the dormer flashing, and then run that step flashing past the dormer flashing the same distance you made your cut. Bend the step flashing around the corner onto the dormer flashing with your hammer.
Install your next row of shingles over that first step flashing, then cover that row with a step flashing, and so on. Nail the step flashing to the wall toward the top of the flashing at the end that’s closer to the peak, so the next step flashing in line will cover the nail. Don’t nail them down through the shingles. For information about flashing around chimneys, see Installing Chimney Flashing.
How Many Layers Of Felt Do You Need
Different roof slopes require different protection for asphalt shingles. The International Residential Building Code states two layers of felt for slopes between 2/12 and 4/12. For slopes greater than 4/12 a single layer of felt is acceptable. The NRCA recommends a double layer of 15-pound underlayment for roofs between 3/12 and 4/12, and a single layer for decks greater than 4/12.
Local codes may have different requirements, and shingle manufacturer warranties often specify underlayment requirements, so check them out too. Heavyweight asphalt shingles commonly have a longer service life. Instead of using lighter-weight 15-pound felt, use the heavier 30-pound felt as it will last longer too.
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Can You Nail Roofing Felt
It is not necessary to completely nail the top edge of the course. A few nails to hold the top in place will be adequate because each top row will become a bottom row once you add another course of felt. Nail down the bottom and middle of the second course of felt with a pattern of nails every 6 to 8 inches.
During Water Or Ice Damage It Works As Backup
Alike in the northern areas, snow dams are the familiar cause of the water damage issue. When the snow gets melt due to residential heat, the water on the roof seeps into the nooks or crannies, ultimately causing damage to the walls, insulation, or ceilings in your residence. The best protective measure for an ice dam is the water or ice protective membrane, but the roofing felt is way more efficient and works as the extra layer for leakage.
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Fold Flashing Over The Peak
Cut the flashing back to the peak along each crease. Then fold the flashing over the peak and cover the cut ends with self-stick underlayment. Roof valleys channel a lot of water, so they need extra protection. Start by installing self-stick underlayment on the decking. This process is much easier with two people. Cut the underlayment to size , and peel off the entire plastic backer. With a person on each end, fold the underlayment in on itself, sticky side out. Then lay it into the valley and unfold it. Try to push it down into the crease of the valley as tightly as possible. If this self-stick ice-and- water underlayment bridges both sides of the decking, leaving a gap underneath, it could tear once you install the metal valley flashing. Run the underlayment past the drip edge at the eaves, and trim off the extra with a utility knife. Once it’s smooth, nail it down on the outside edges.
Finish installing felt paper on the rest of the roof, overlapping the self-stick underlayment. Be careful when you trim back the felt paper so you don’t slice into the underlayment. Photo 7 shows the underlayment covering the felt on one edge a couple of inches. This will keep water farther away from the inside corner of the fascia. You can extend the center out even more but not so far that water overshoots your gutters if you have them.
How To Install Roof Felt
Installing a felt roof is an easy and cost effective way to protect a shed, garage, or flat roof. Roof felt is pliable and can be fitted nicely against pitched and curved roofs, its applied in layers and covered with a waterproof material which should give you upwards of 20 years protection.
In terms of cost, a small shed should cost in the region of £50 – much cheaper than alternatives such as rubber or fibreglass. A small shed should take just a couple of hours, so even a garage or shed can be done in a day.
This job can be undertaken with no specialist tools, and no naked flames. We recommend you select a professional grade roofing felt no matter the size of the job, its far more durable and will withstand weathering – cheaper alternatives can easily become weakened and tear, leaving you repeating the job inside 20 years.
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Where Does The Drip Edge Go On A Roof
Drip edge is installed around the whole perimeter of the roof . It is used to hold the underlayments down and create a watertight seal around the edge of the roof . Only the face of the metal is seen and is usually just white one to one and half inch stripe located right under the shingles and above the fascia.
Roofing Felt Installation Details
Reader questions on roofing felt installation specifics
Anonymous said:
Hi Dan, a couple of roofing questions:
1) We often see roof felt stopped short of the eaves. Builders argue its not a problem. I once had a written opinion from NRCA stating felt needed all the way to the eaves but can’t find it anymore. Any known reference clearly indicating need to felt to eaves?
2) Asphalt shingles on less than 2:12 pitch, builder says ice& water shield under it, I know that’s not OK but again any reference source you may know of?Hope all is well in NY land, nice here in Raleighwood. – Steve Smallman –
Reply:
Thanks for the important questions Steve:
1. Felt underlayment omission from some roof areas: this defect – taking a shortcut by leaving off some roofing felt, is an example of a wider problem: building codes & standards writers have given up on trying to anticipate every possible way that people can make a mistake, shifting instead often to “performance” codes that give the general intent of the code. So we’ll have trouble finding an explicit citation for your question part 1.
But a reading of roof shingle manufacturer’s specifications for using an underlayment does not find any exceptions that allow leaving out some of the coverage area.
I’d excuse the omission of felt at the eaves and at rake edges of a roof IF instead the roofer is installing a stick-down impermeable barrier such as ice and water shield. Otherwise it’s a mistake.
Also see ROOFING UNDERLAYMENT BEST PRACTICES
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