[JohnMargaret]

Hello,

Purchased a house a year ago only to find that the front porch floorboards showed signs of bad rot recently. Porch is open and floor is fir wood. Contractor pulled up the rotten boards and found the following:

top layer of fir boards had been eaten from under by carpenter ants/bad water rot
under that was a water/ice shield that the boards had been nailed into
under that was a sheet of wood
under that are the joists
under that is the basement/garage

Contractor is saying the porch was built incorrectly (old house - 1920s), that sleeper boards should have been used and that the porch really should be enclosed to prevent this from happening again. He says the issue is that the area under the porch is not open, so water gets stuck between the porch and the basement/garage causing the rot. The porch was just redone in 2001 and just recently started to show the rot in a few sections.

Has anyone experienced this (personally or professionally) with a house/porch? What did you do to resolve the issue? I really do not want to enclose the porch since it is a beautiful open one and I am leaning towards having the contractor redo the entire floor with a new ice shield, sleeper boards, and new top boards (all fir wood).

Would love to hear if anyone has seen this before.

 

[JohnMargaret]

Also, I tried searching for other posts on this topic but was unable to find anything.

 

[joecaption]

Going to need some pictures.
There needed to be a sloop and storm and Ice is for roofs not for under decks.
There should have been a one piece membrane under it.
You would be far ahead to have a roof and enclose it.
Did they not even use pressure treated wood?

 

[JohnMargaret]

Hi Joe,

Sorry- yes, it is currently a membrane but the contractor has called it both a membrane and a water/ice shield so I thought the two were the same. I guess they are not?
No, it is a front porch and is fir, not pressure treated.
There is a roof but no windows. I will add a picture once I figure out how to upload one

 

[orange]

Pictures, pictures..... would be a big help as Joe said.

 

[cortell]

What exactly do you mean by "Porch is open". No cover over the porch? So, basically a patio/deck? Or do you mean it has a roof, bit it's not enclosed on the sides? This is why without pictures, we end up having to do a lot of guessing.

I'm with joecaption. Even with a cover/roof, a porch is going to see a good amount of wind-driven rain. But if no cover, that deck is going to see a LOT of water. That water needs to go somewhere. With the porch/patio floor sitting over flat structure (garage), I'd expect problems more serious than rotting deck boards. Ice & Water shield (that's a membrane, BTW) is a backup to save the day when the building elements designed to keep an area dry don't work 100%. And so it's effective, but only to that limited capacity. In your case, it was installed to function as the primary defense against direct water contact. Are you not experiencing any signs of water damage in the basement/garage ceiling, under the porch? If not, you may want to call the Vatican and report a potential miracle.

Then again, without pics, we're somewhat shooting in the dark here.

 

[JohnMargaret]

I have been trying to find a way to upload pictures.
My porch has a roof but the sides are open.
No issues in the basement/garage as of yet and I live in New England where we have gotten a whole lot of snow and rain.

Here is a picture:

 

[cortell]

I have been trying to find a way to upload pictures.
My porch has a roof but the sides are open.
No issues in the basement/garage as of yet and I live in New England where we have gotten a whole lot of snow and rain.

Here is a picture:

Ahhhh...I do believe I see skuppers there. That explains a lot. So, chances are that porch is sloped, and thus designed to drain. This means you probably didn't have much standing water on that Ice & Water Shield, and because the porch is covered and partially enclosed on the perimeter, the membrane was able to fend off water intrusion. Still, I wouldn't have relied on it.

Anyway, if and when you experience water damage in your garage ceiling, that will be the indication your luck ran out. Hopefully that never happens.

So, on to the active problem...the porch decking absolutely should not rest directly on the membrane. You need air space between the membrane and the decking. This is accomplished with sleepers, as your contractor said. So, I think you're on the right path. However, just removing the decking, putting in sleepers and throwing new decking on top of that would be dangerous, IMO. Because the existing decking is fastened through the membrane, pulling up the decking means you will be exposing hundreds of holes in the membrane. That WILL result in water intrusion down the road. At a very minimum, a new membrane is needed.

Which brings me to my final point: instead of replacing an inadequate but lucky membrane with the same, I'd call in a roofing company to seal the porch subfloor just as if it was a flat roof (which it effectively is). Then I'd put a floating sleeper skeleton on top. Do not fasten the sleepers to the subfloor, as that would immediately compromise the new "roof" you just paid a lot of money for. Then, finally, the decking on top of the sleepers.

 

[Joe47]

I have basically the same problem. I do have a roof over the porch and I know that I have to stop the water from getting in from the back and side walls but I want to make sure that water doesn't accumulate or sweat between the mortar bet and waterproofing membrane. I'm in Fayetteville, NC so we don't get a lot of snow and the original porch was put down in 1978. I see that your message was in 2013 so I hope you have gotten your porch fixed by now.