Do you unzip vinyl siding?

Do you unzip vinyl siding?

I began doing this a few years ago regularly and now cant imagine doing without. I have found so many homes with rotten OSB sheathing it is scary to think what others may be missing. I know many don’t do this and I understand risks but I explain to the clients (if they see me do this) that it is still very limited but the reason I do it is because I often find rotten sheathing without an underlayment. It seem like the late 70’s to late 90’s rarely had an underlayment. The j channel and limited taping or caulking around the windows and doors allow in more water than I imagined. Now when I find no felt or wrap under vinyl I disclose this and check under a few windows. I have cracked a few pieces of siding but it is rare and I’m getting better at it. Most often under windows and were roof and wall intersections meet and lack kick-outs do I find this.

I know it exceeds the SOP and can in some cases increase liability but do the ends justify the means??? I don’t automatically do this on every home but I do open butt joints on all to see if an underlayment exists. Then if none exists I usually decide to unzip under a few windows.

A recent inspection proved this for me. I found no underlayment and checked two windows and one area under a wall to roof intersection and the sheathing was damaged so I called it out for “further evaluation” but speculated verbally that it most likely existed in several areas. Well just got a call from the buyer asking for me to inspect another home. She stated the realtors involved bashed me to no end about this and then said they would hire another inspector and contractor. The inspector gave the entire home a flawless report. I noted 50 or more maintenance and areas of concern or plain defective items including the sheathing rot. The inspector was not told about all of these issues and walked through the 12 year old $450K 5300sf home and found no issues. Then the contractor was told to check for the rot under the windows and after removing a lot of siding estimated roughly 40% of the sheathing and insulation had to be replaced and the whole house re-sided. I didn’t get a price but $$$$

Just wanted to see what others are doing and maybe send a cautionary note to all to at least look for underlayment. A zip tool is $5 but has saved myself and my clients big$$$.


Hi Aaron, nice toppic and thought I would share to all the members what a Zip-it tool is.

The Vinyl Siding Removal Zip Tool I believe what you are doing is fine to discover what the substrate condition is under the siding, but I would not condone it as a Home Inspector, because for one, it is invasive and the increase in liability is way too high. The age of the House most time can be established to be a known quantum, but the age of the vinyl is unknown and some of these products have been discontinued. To unzip vinyl siding you are taking chances that breakage and chipping of the material can occur, then what if you can not repair it? To unzip to merely find out if the under layment is installed is not a valid deduction. If you want to know if an underlayment is behind it, you just push on it. Chances are you will find that there is either OSB, Plywood, or Celetex Board for backers and possibly foam board.

To unzip to check and see if the underlayment is rotten, well since the Codes don’t require a weather barrier under the vinyl siding, chances are there is none and the vinyl siding is hiding what people did not want to see before. Chances of having rot behind the vinyl siding, is a given unless it is a new construction where there is a 50-50 chance that a weather barrier was installed. You can continue to do this, but I would caution anyoneelse to beware of the consequences. Hope this helps some. Marcel :slight_smile: :slight_smile: </IMG></IMG></IMG>

I would never un-zip siding and I learned the hard way. I did an inspection on a mobile home and the homeowner was supposed to open the vinyl skirting, which they didn’t. I figured what good is my inspection if I don’t go under it. Well I broke the vinyl skirt and had to go back and fix it.

Every time I tried to attach the new skirt to the old I broke another piece. I bet I ended up replacing about 12 feet of skirting before I finished.

Didn’t make any money on that one.

I agree Marcel, but I do carry a zip tool in my bag, and if I suspect issues, I will open it up, and yes, you do discover some very bad issues sometimes.
I believe using a zip tool is like many decisions we all make for ourselves, (like walking roofs;-) , going in attics, etc.) do what your comfortable doing with your knowledge, experance and expertise.:slight_smile:

Hi. John;

I also have one in my basement, just in case ha. ha.

Since I have the knowledge and Experience to unzip, one might say I do it everyday, but no, I choose to do it in a fashion that will not be evasive so not to find myself there the next day fixing something that broke. And that is assuming you can find the Product replacement.

I choose to use other inspection techniques that will give me clues as to why the siding is there and what is it hiding.

In older re-sided Homes, you can always look underneath the starter strip of the siding and see the exterior sheathing and building paper if any.
Since water intrusion would dictate that water travels downhill, the water concentration of the substrate would be at the bottom. Similar to the principal of weep holes in brick facade.

Other clues would be at J-moldings around windows.
Most J-moldings can be pried away from the sheathing in between the nailing patterns and observe weather barrier or sheathing types.

There are always sloppy installation details that one can observe and take advantage of without making it an evasive inspection.

To me, unzipping siding would be like a comment on an earlier post of peeling the carpet corners of all the rooms of the house to identify the underlayment material.

We have to set a guideline somewhere and I believe the SOP has done that.

Marcel :slight_smile: :smiley:

I think a significant point worth making is that while codes may not require an underlayment under the vinyl, in new construction it only makes good building sense. A lot like installing roof shingles over felt-paper when you think about it. At least some vinyl siding manufacturer’s flat out state in their product installation and warranty information that the vinyl siding alone is not to be relied on by itself, to prevent weather intrusion. These manufacturer’s state they will not warranty the performance of their vinyl siding product unless installed over some type of barrier behind the vinyl, be it felt paper, Typar, Tyvek, generic house wrap, fanfold, or whatever. If its supposed to be there and its not there, then I report it. The week before last I inspected a little rancher with at least 4 holes in the vinyl where you could clearly see the fading OSB directly behind. I had to point it out the holes how could I not mention the lack of a barrier? Personally if I were buying, I would want to know if it’s there or if it’s not there, and what that may mean if it is not there. I don’t consider popping open a butt joint of horizontal vinyl for a confirmatory peak as “intrusive”, any more than removing a panel cover with a screwdriver would be “intrusive”. I’ve never broken a piece, but I’m real gentle in cold temperatures.

When you know that a certain practice occurs in an area such as no sheathing membrane /weatherbarrier/underlayment and that practice can result in substantial damages to a dwelling, then I think it is imperative that a check be made such as opening the vinyl siding at an overlap seam or un-zipping a piece of siding at an appropriate location. We are being **paid **to find any existing problems with dwellings and the SOP are only a minimum set of guidelines (and a poor minimum in my estimation) so that at least some level of performance can be expected by our customers.

How many of us here would build their home to the minimum code levels or want an inspection done for themselves to just the SOP??? Likely not many! So let’s give the customer what they deserve…better than minimums. Afterall, without them, we are nothing.

I do many things beyond the SOP and thus my inspections take longer which pees off many realtors. Although I give them cards, I never seem to get any work from them until…they want an inspection for themselves, a friend or a family member. And then that friend or family member will spread the word about how thorough I was and the referrals start to come to the chagrin of the realtor since they now have to deal with my longer inspections more and more.


Inspected a house for my Daughter this morning in Caribou, Maine, where it is still 36 degrees in the morning.

The house was built in 1959, so I new pretty much what the siding was covering up. Sure enough the sloppy installation show T-111 hanging down about an 1" below the starter strip, and looking underneath the first course was the t-111 no weather resistant barrier underneath the vinyl and #15 felt behind the T-111 and 3/4" boards under that.

So looking underneath the starter course will tell you alot without the unzipping.


Marcel :slight_smile:

All my reports have this disclaimer: “The wall sheathing beneath the siding may or may not be covered with a water proofing membrane, commonly called “house wrap”. While it may not be required, it is recommended but we do not verify its presence or absence or otherwise view behind the siding because to do so would require dismantling the siding system.”

I don’t dig up underground pipes either to verify they are not leaking.

Good Question! I’d say sometimes. But , if your going to look behind vinyl , you may have a repeat customer ask why you aren’t looking behind aluminum , asbestos , asphault , cedar , stucco , etc… Most of the time siding materials were installed as a means of maintanence. For the most part , siding applicators , as well as other contractors took pride in thier work. That was , until vinyl hit the market. Vinyl was used to cover up all kinds of sin , in bad need of repair/replacement. Being in the siding business for 30 years , I’ve seen a lot. From an inspectors stand point , I’d say look where the siding panels over lap. And leave it at that. From a contractors stand point , I’d say open it up. If you’re going to unzip the vinyl , you should have a good zip knife. Not that piece of junk shown in this post. The best kind of zip knife is the old “Bird” style , with the heavey wooden handle.

If you unzip siding to see what’s covered up, do you also pull back wall-to-wall carpeting to see what’s covered up? Pull roof shingles, etc? Just playing devil’s advocate when it comes to a visual inspection.

A lot of that stuff becomes brittle , so watch out about recomending to the rank and file .

Came across this today after viewing water damaged drywall/sheathing inside the garage.


I don’t unzip it, but I’ll peak through an overlap. Sometimes, as was the case in yesterday’s inspection, I’ll stumble across a piece that is loose and get a good look.