How to Install Liberty Low-Slope Rolled Roofing System

Are you looking to install a new low slope roof or do a re-roof on your home? With all the roofing products out there, it is really important to find one that will be reliable, durable, long lasting and leak-free for many years.

In the low-slope roofing market (roof pitch between 1 and 3 in 12), one product you can install yourself, is a Liberty roofing systems – an SBS modified bitumen roof. These systems are manufactured by GAF and are specially designed for low slopes with a pitch of 1/2 to 6 inches per foot. This product line consists of 3 membranes: the cap sheet and two base sheets: mechanically attached and self-adhering. You can either install one of the base sheets with the cap sheet on top, or for extra protection you can install the Liberty Premium 3 ply system, which includes the mechanically attached base sheet first, the self-adhering base sheet next and the cap sheet on top.

You can also use the Liberty roofing system for flashings at parapets, perimeter terminations, and typical roof-top penetrations, skylights.

Liberty Low-Slope Roof System overview:

Note: Liberty self-adhered rolled roofing system is a good product for DIY homeowners who do not have access to EPDM Rubber Roofing, and it is also easier to install and provides better puncture resistance than rubber roof.

Products like liberty are perfect for roof application on sheds, porches and other structures with low slope roofs, and they last a lot longer than traditional rolled asphalt roofing. However, liberty should never be used on completely flat roofs, or roofs without positive drainage, as this will not only void your warranty, but will also cause multiple roof leaks. For completely flat roofs, we recommend using PVC single-ply flat roofing membrane.

Installation of Liberty Rolled Roofing System:

Any roofing products is only as good as its installation, and Liberty products are no exception. Consequently, if you are installing the roof yourself, it is imperative to follow the right installation procedure to make sure that your new roof will be watertight. Our installation overview provides critical information you need to know prior to beginning your Liberty system roof installation.

To ensure proper adhesion of any Liberty self-adhered system it must be installed when the weather is dry and 45 degrees F. or higher. Liberty 2 & 3 ply systems are accepted and covered by the Golden Pledge and Systems Plus Ltd. warranties on low slope areas of shingle projects.

Take care of the substrate prior to installation

To ensure that your installation goes smoothly and successfully, the substrate must be clean and dry.
The substrate for the Liberty system must be clean and dry. All penetration curbs, perimeters, “kents, nailers”, must be in place???

Installation of Liberty Mechanically Attached Base Sheet (Liberty MA Base)

Liberty Mechanically Attached Base Sheet is a one meter or 39 and 3/8 inch wide membrane with a plastic film on top, designed to maximize the attachment of other self-adhering Liberty Membranes. This sheet can be mechanically attached directly to the deck or installed over ISO insulation. Over nailable decks, the sheet can be nailed with a typical base sheet pattern, using 1 inch square or round cap metal nails.

Important installation tips:

-You should let the sheet relax and remove any wrinkles to provide the smoothest surface for other plies.

-All Liberty systems require installation of primed metal drip edges on eaves and rakes.

– Make sure you use the correct adhesives and cements with Liberty roofing systems. All of them require the the use of SBS Adhesives and cements, as other none-SBS cements may have an adverse reaction and damage the Liberty membranes.

– To create additional wind uplift resistance, apply a bead of caulk in the overlap between the base sheets, and then nail the the overlap area a minimum of 6 inches on center.

– To reduce the risk of leaks, you should off-set the end laps in the adjacent course a minimum of 36 inches.

Installation of the Liberty Self Adhering Base Sheet

The Liberty Self-Adhering Base sheet is also a 1 meter or 39.375 inch wide membrane that has a plastic film top surface designed to receive the liberty cap sheet. On the bottom, the surface is a split back release film, designed to to be removed to uncover a self-adhering surface. Often, the self-adhering base sheet is a more popular choice, due to easier and quicker installation as compared to the mechanically attached base sheet. One major advantage of the self-adhering membrane is that it has superior self – adhering properties.

How to achieve the strongest adhesion bond during installation

When installed, directly to wood, the membrane will adhere very strongly. While it is possible to achieve decent adhesion to wood, without primer, the best and most long lasting adhesion can be achieved, if you prime the wood with one coat of matrix 307 asphalt concrete primer or a comparable ASTM D-41 type primer. It is important to allow the primer to dry completely prior to the installation of the self-adhering base sheet. This gives the self-adhering membrane an asphalt surface to bond to, so when the deck moves, the self-adhered base sheet can move with it. Priming is option, if you are applying the self-adhering membrane to the mechanically attached base or a wood deck.

Important installation tips:

– During installation, firmly press the sheet to avoid wrinkles and trapped air, as the ply adheres to the deck or to the mechanically attached base sheet, and press down the faccia.

– When adding additional length of Liberty base ply to the same course, you need to overlap the end of the previous sheet a minimum of 6 inches, which will create the best protection against leaks.

– After you finish applying the Liberty self-adhesive base sheet, apply uniform pressure to the entire area by using a either a long-handed push broom or a weighted roller. Do not skip this step, as this will ensure a solid bond between plies. Brooming also provides a clean surface for adhesion of the liberty cap sheet.

Installation of the Liberty Cap Sheet

Important installation tips:

– Before installing the cap sheets, let them relax on the roof. By allowing the ends of the rolls to lay flat, you ensure a much better finished look.

– To seal one row with another and to minimize the possibility of “lack blisters” forming, apply a bead of Leak Buster Matrix 201 Premium SBS flashing cement adhesive along the top edge of each cap sheet and of any salvaged edge T joints in any self-adhered system.

– It is required to install a bead of Leak Buster Matrix 201 Premium SBS flashing cement at the top of each Liberty Cap Sheet course on all Golden Pledge Installations.

– To prevent membrane movement on roof slopes with a rise greater than 1 inch in 12, back nail in the salvage area at 18 inches on center with roofing nails or cap nails.

– It is highly recommended to leave a minimum of 8 inches of release film on the back of the overlapping cap sheet. This prevents unwanted bonding to the granular surface of the underlying sheet when installing the adjoining sheet.

– To ensure proper adhesion of the cap sheet, apply uniform pressure to it using a broom or a weighted roller.

-If you have any remaining adhesive bleed out, you can cover it with loose granules, to achieve a more professional and nice-looking appearance.

Flat Roof Repair – Modified Bitumen rolled roofing

Flat roof leaks and flat roof repair are often very different and require professional “look” at the roof leaks issue. For most homeowners, flat roof leaks are very frustrating, because only few roofing contractors have the skill and knowledge to properly diagnose and repair leaking flat roofs.

We often get questions from homeowners about their flat roof leaks and this time we were contacted by one such homeowner from London, UK about his roof leaks, and wanted to share this with you as it might be helpful for many other homeowners with flat roof leaks.

Below is a conversion with Ajay – the homeowner with leaking / damaged modified bitumen flat roof (we’ve attached roof pictures that came with each email):

Hi Leo,
Sorry for emailing you “out of the blue” like this but I found one of your posts on this website (Flat Roof Repair article on and thought I would seek your advice. If you don’t feel comfortable
giving advice to a stranger like this, then I fully understand!

The problem is that my neighbor is doing building work and one of his builder’s scaffolding planks fell into our flat roof and made a
dent/hole in the roof. It’s been two weeks now and they haven’t had the courtesy to fix it and I’m now suspecting there could be water damage as it has rained quite a bit over the past few days (I live in London).

I hope you’ll be able to offer some advice as to what needs to be done to do a proper professional repair. I was thinking of going with the
EPDM option – how should this be sealed? What do we do about the board underneath? Do we go with 2-ply 25mm waterproof marine plywood? I’ve attached photos so you can see exactly what the damage is.


Mr Ajay

image of leaking flat roof


My response:

Hi Ajay,

Judging from pictures, you have a rolled asphalt roofing OR granular surface modified bitumen (though I think it’s the first one), that is adhered directly over OSB – particle board.

I doubt there is much rot damage, though the in area right around the hole, the OSB composition has probably weakened. Do you have water stains inside?

I think you should talk to your neighbor to have this fixed OR have your insurance company go after your neighbor and the contractor who damaged the roof – this will force them to get the contractor to fix the damages … or something like that.

As for repair – you cannot use EPDM rubber to fix it. You will have to use same or similar roofing material and all seams will be done either with TAR or torch (if it is mod. bit. roof). Tar does not hold too well, but I guess it held so far.

You would need a whole section replaces – not just a patch, as patch will not hold long. Best bet, is to replace the whole thing if possible, as it looks like a “hack job” to me – the seam overlaps are in the wrong direction – they should be facing the roof slope – away from the building. Insetad the face the building, so all water running down, catches seams.

I don’t know about your local building codes, but 25mm (about 1 inch) waterproof marine plywood seem EXCESSIVE to say the least.

Typical roof deck here in US is 5/8 inch 4-ply regular plywood, and “overkill” is 3/4″ … that’s when your rafters are spaced far apart.

Bottom line – most hack roofers will will throw a bunch of tar on top of the hole, maybe a mesh and more tar. This would work for short time (maybe a year or two). The correct way to fix this would be to replace a section, which can tear the adjacent sections … hence I recommend the replacement if possible.

My reasoning is that they damaged your roof, and throwing tar on it will not make it “whole” or in the same condition as it was – it will be merely a temporary fix.

One more thing – you need a professional roofing company to fix this – not the contractor who caused the damage – they have no clue about flat roofing!

I believe I know a company in London … I’ve seen their work on YouTube and the seem to know what’s up.

Good luck.

Leo – Project Manager –

Second email from Ajay:

Hi Leo,

Thank you so much for your detailed reply. It was most helpful! I’ve had a temporary fix job – a piece of plywood to plug the hole (which their roofer made bigger by cutting away for a closer inspection), then he put some kind of felt??? on top, then he covered the whole lot with some waterproof material(???) and sealed it with tar/bitumen by torch. I’ve attached the photo of the completed work. I’ve also arranged for a professional roofing company to do the permanent fix on Thursday.

If you wish, you may post the conversation on your website to avoid repeat questions and to help others.

Can I ask you another question please related to water leakage through small holes where felt on a flat roof has come away from the main
building wall? Is it best to use lead flashing to seal the felt to the building wall or can some other material be used i.e. the same material
that’s used to fix the actual roof? I was told that if some other material is used, it might start coming away from the wall and leave gaps.



Image of flat roof repair


image of Modified bitumen flat roof repair


My second response:


Hi Ajay,

As far as roof to wall flashing – you need the roofing material to run up the wall, and then use lead or aluminum counter-flashing. You may also seal the roofing material to the wall, but the counter flashing is the best way. Using both, is preferred – seal to the wall and use counter-flashing.

If you do seal to the wall, I would recommend using roofing grade caulk + water stop (also called water cut-off – a caulk than never cures) and a termination bar with masonry anchors to attach the roofing material to the wall firmly.

There are plenty of pictures on our site if you dig deep enough for you to see how this is typically done.

Good luck, and let me know how it goes, and send some finished pictures. I will post this on one of our sites soon.

Sincerely, Leo.

We will continue to post updates to this flat roof repair, as Ajay sends in the update on how things go, and more pictures. If you have flat roof leaks or roof repair issues that you want to discuss with us and get our help with, send in your questions and pictures. You can post them in the comment section below and we will try to help you out as much as possible.PS – the reason we are posting this email is to helps other homeowners with similar flat roof leak problems and with Ajay’s permission. Because many flat roofs have EPDM Rubber Roofing material installed on them, which often leaks, you can post your rubber roof repair questions on our Rubber Roofing page.

BONUS VIDEO: How To Repair a Tar Flat Roof: