Installing Drip Edge & Self-Adhering Modified Bitumen

[jar546]

I have 2 items for this post to discuss. The first is a major pet-peeve and the 2nd is something that I did not know. Let's start with what I did not know:

I did not know that some OSB have a factory-applied coating that can interfere with the bonding of self-adhering modified bitumen. In some cases, you have to apply a bonding agent first. This, I did not know. In Florida I really don't see any OSB and I only see plywood on roofs and sometimes for a 2nd floor...floor. That is it. We are all CMU & slab around here. If I were still in Pennsylvania, this would be a really big deal. I am embarrassed to say that I did not know this.

Now for my 30 year pet peeve. If you see the figure below, you will notice a few things:
1) The drip edge and bitumen are installed in 'shingle' fashion.
2) First you install the bottom edge drip edge
3) Then you install the bitumen
4) Finally you install the metal drive edge of the rake end.

There is no other way to do this that makes sense. If it is not installed this way, it is wrong. Wrong, wrong, wrong if it is done any other way.

 

[mtlogcabin]

There is no other way to do this that makes sense. If it is not installed this way, it is wrong. Wrong, wrong, wrong if it is done any other way.

Think of ice and water shield put the 1st layer down 12 to 24 inch strip then the metal drip edge then the next layer to cover the entire roof. This is how we did it except we would spread a layer of bull and set the drip edge in it. Remember though I am referring to very low slope pitched gravel roofs where the drip edge had a 1 inch lip turned up to help keep the gravel from washing off the roof

 

[steveray]

Except the ice dams back up out of the gutter under the dripedge and between the facia and roof deck....A good roofer goes under (onto the facia) and over....

 

[Mr. Inspector]

So your saying that we will need the OSB manufactures installment instructions for every house that uses OSB on their roof? It's used here about 99% of the time here. This could hold up a lot of roof repairs.

 

[jar546]

So your saying that we will need the OSB manufactures installment instructions for every house that uses OSB on their roof? It's used here about 99% of the time here. This could hold up a lot of roof repairs.

There are only so many manufacturers that service a specific area so it may be beneficial to do your own homework to determine which brands and types do require this and this way you already know ahead of time.

 

[Robert]

I have 2 items for this post to discuss. The first is a major pet-peeve and the 2nd is something that I did not know. Let's start with what I did not know:

I did not know that some OSB have a factory-applied coating that can interfere with the bonding of self-adhering modified bitumen. In some cases, you have to apply a bonding agent first. This, I did not know. In Florida I really don't see any OSB and I only see plywood on roofs and sometimes for a 2nd floor...floor. That is it. We are all CMU & slab around here. If I were still in Pennsylvania, this would be a really big deal. I am embarrassed to say that I did not know this.

Now for my 30 year pet peeve. If you see the figure below, you will notice a few things:
1) The drip edge and bitumen are installed in 'shingle' fashion.
2) First you install the bottom edge drip edge
3) Then you install the bitumen
4) Finally you install the metal drive edge of the rake end.

There is no other way to do this that makes sense. If it is not installed this way, it is wrong. Wrong, wrong, wrong if it is done any other way.
View attachment 7002

Agreed, I don't use osb on horizontal surfaces or roofs....it's oatmeal when it gets wet. Sika makes Hyflex 407 specifically for surfaces that don't stick well (like osb and peel and stick membranes). I know Grace has a newer peel and stick specifically for osb for the same reason.

 

[MACV]

From GCP Technologies (Grace):
"GCP’s underlayments (Grace Ice & Water Shield® , Grace Ice & Water Shield® HT, Grace UltraTM, Grace SelectTM, GCP granular underlayment, Roof Detail MembraneTM,Tri-Flex® andTri-Flex® 15) are recommended for use ove rOSB substrates. However, in some instances the ability of the self-adhered membranes to adhere to the substrate may be compromised by the level of surface texture, the amount of wax added to the panel, and job site wind conditions.
In applications where membrane adhesion to the OSB is found to be marginal, or windy conditions are likely prior to covering with the exposed roofing materials, nail off the perimeter of the membrane with roofing or cap nails at intervals of 12 inches (300 mm) on center. If moderate or high wind conditions are likely, additional nailing in the field of the sheet may be necessary. Staples should not be used in place of nails.
®22®
As an alternative to using nails, apply Perm-A-Barrier WB Primer to the roof deck at a coverage rate of 250–350 /gal (6–8 m /L). Perm-A-Barrier WB
Primer and the surface of GCP’s underlayments are slippery when wet. Allow the Perm-A-Barrier ® WB Primer to dry thoroughly before walking on the OSB surface. Cover the membrane with the exposed roofing material as soon as possible.
The long-term adhesion of GCP’s self-adhered underlayments to the textured surface of OSB is excellent and membrane performance is not affected."

I have used Grace's WB (Water Based) Primer on fiberglass faced sheathing and concrete. When properly applied, it's impossible to remove the self-adhering membrane without separating the poly sheet from the modified bitumen.

 

[jar546]

From GCP Technologies (Grace):
"GCP’s underlayments (Grace Ice & Water Shield® , Grace Ice & Water Shield® HT, Grace UltraTM, Grace SelectTM, GCP granular underlayment, Roof Detail MembraneTM,Tri-Flex® andTri-Flex® 15) are recommended for use ove rOSB substrates. However, in some instances the ability of the self-adhered membranes to adhere to the substrate may be compromised by the level of surface texture, the amount of wax added to the panel, and job site wind conditions.
In applications where membrane adhesion to the OSB is found to be marginal, or windy conditions are likely prior to covering with the exposed roofing materials, nail off the perimeter of the membrane with roofing or cap nails at intervals of 12 inches (300 mm) on center. If moderate or high wind conditions are likely, additional nailing in the field of the sheet may be necessary. Staples should not be used in place of nails.
®22®
As an alternative to using nails, apply Perm-A-Barrier WB Primer to the roof deck at a coverage rate of 250–350 /gal (6–8 m /L). Perm-A-Barrier WB
Primer and the surface of GCP’s underlayments are slippery when wet. Allow the Perm-A-Barrier ® WB Primer to dry thoroughly before walking on the OSB surface. Cover the membrane with the exposed roofing material as soon as possible.
The long-term adhesion of GCP’s self-adhered underlayments to the textured surface of OSB is excellent and membrane performance is not affected."

I have used Grace's WB (Water Based) Primer on fiberglass faced sheathing and concrete. When properly applied, it's impossible to remove the self-adhering membrane without separating the poly sheet from the modified bitumen.

Great information. Thank you.

 

[SCBO1]

I did not know that some OSB have a factory-applied coating that can interfere with the bonding of self-adhering modified bitumen. In some cases, you have to apply a bonding agent first.

I did not know this, thx