Hello all,
New to the forum here. A few weeks ago my basement flooded and I ended up cutting the bottom 12 inches of drywall out around the perimeter of my entire basement. Now this is my first time doing drywall work like this and I ended up cutting the wall very poorly when removing the bad stuff. The cuts are very wavy so needless to say there are some gaps up to 1.5 inches wide. Is that too much gap to fill with mud? If I am filling a large void with the mud is there a chance of it cracking even it I use tape? Starting over and cutting straight lines is not an option at this point as I already have most of the drywall screwed to the wall. My plan is to slop the mud in the gaps and let it dry then mud and tape and then few more layers to feather it out. Also what kind of mud is the most crack resistant. I saw someone suggested using concrete patch filler to fill large gaps like this. Anyone ever hear of that? When the mud cures, does it actually bond to the drywall as 1 or not.

 

Welcome to the forums!

How you fill a gap will depend on how your wall is constructed. If you have just drywall for your wall surface you will want to add a ripper as best you can to fill the gap You might need to add some strips of wood for some backers to screw to, or just make a larger, better cutout to fill with drywall. (draw a line with a straight edge before cutting. )

However, if your wall has something behind the finished wall like lath, then you could use a setting type compound such as Structolite, Durabond, or lightweight setting compound. The first two are good for filling gaps, but not good for the finish coat. The setting compound is better for a finish as it sands easier then the others. It is still not what I would recommend for finish taping.

Either method you use you do not want to just fill the gap and go. You want to fill it even with the surrounding drywall. Then lay down your paper tape and finish with two more coats of regular mud. This should give your patch the best chance of not cracking.

You do not want to use concrete filler. It is much too rough and there are better products that are designed for your application as I have outlined out above.

 

Yes, add a ripper. You can cut more out of the gaps to make them more consistent... then fill them in as best as you can with a ripper- a skinny piece of drywall. (if you have 1 1/2" gaps, hold a 2x4 on edge against the wall, draw a pencil line on each side and then when you take the board down, cut along that line with a knife. Then you can cut some 1 1/2" strips of drywall and nail/screw them on.) You really don't want to fill any bigger of a gap than you have to. IMO a 1/2" gap is too big to prefill.

I mix up some 5 minute setting compound for prefilling gaps, but not for gaps larger than 1/2".

 

Here's the problem I have. 2 of the walls are exterior walls. They are just the foundation with 2 inches of Styrofoam board insulation glued to it. The studs in the walls are running horizontal... Not vertical. So stupid. I cut it and didn't cut it at the stud. I just went about a foot up and cut a rough line with my oscillating multi tool like an idiot. Then got the pieces roughly screwed in place and now I question how this will work with filling with so much stuff. I installed another horizontal stud (drilled into foundation and tapconed a 2x2 to the wall sandwiched in between the Styrofoam above and below) and fastened the new drywall to the studs. Doing this created another problem. The sheets above my cut have no support on the bottom now. I can't really install a stud for the upper pieces (due to being an exterior wall and the foam sheets, unless I just don't know the way) I didn't check where the next highest stud is located so I don't know how high up from the bottom of the cut the next screw holding it to the wall is. Could this bow out over time after they are mudded together? I'll get pictures tomorrow.

Thanks for your help!

 

Sounds like you need to cut that gap a bit wider (minimum 1 1/2") like we were mentioning and slip in some short pieces of 2x2 or 2x4 that maybe you can flip up on end with your fingers so that they sit vertically behind the entire joint. If you can just insert something every 16" or so that both upper and lower pieces of drywall can screw to, you should be good. If screwing the bottom piece of drywall to these short pieces isn't possible, you might have to glue the end to your new horizontal stud with construction adhesive.

 

I wonder if I could get some kind of sheet metal behind there... Screws should hold to that just as well as my metal studs I suppose.

 

it needs to be a spacer to solidly fill any gap between the drywall and the foam so that if the wall is bumped the joint won't crack.

 

Something like this might be of help to join the two drywall pieces together:



Should slip between the foam and drywall.

 

That's pretty much what I need I think. Any idea what one of those is called or where to get those?

I really have barely any gap between drywall and foam since the studs are 2 inches and there is 2 inches of foam board so it's just about flush.

Also, to install the horizontal studs, I drilled about 3 to 4 inches into my foundation wall. The put tapcons in. That's shouldn't introduce a new water leak right? My concrete walls behind the foam insulation board had a coat of white paint or sealer on it FYI.

 

How is your foundation wall constructed? block, poured concrete, something else?

It's never a great idea to drill into a foundation wall that is below grade. It may not leak but if water ever gets to that point it has a ready made exit towards your basement. Ideally a stud wall is erected in front of the foundation wall with an inch or so air gap between the two.

 

Pretty sure it's poured unless it's block and they plastered over or disguised it or something. How can I be sure.

 

Can you see the foundation wall from the exterior? or is it covered with brick or stucco?

 

also I'm pretty sure I did not drill all the way through the wall. I think that the wall is supposed to be at least 8 inches thick. Does that still put it at high risk for a leak?

 

I know you didn't drill all the way thru. Your foundation wall should be a minimum of 8" thick [might 12"] The danger is if the masonry starts to get saturated with water, the drill holes make for an easier exit. It may never leak but it's not as bullet proof now as it was before the holes were drilled.

 

For some reason I was picturing the 2x4's on top of the foam. Maybe a heavy gauge sheet metal would work, at least to tie the pieces together so that they don't want to move independently. The fine threaded drywall screws are for metal.

 

The exterior foundation is covered with stucko. I shall try to scratch some off and maybe then I will see it. If not block or poured what else could it even be?

 

also as far as placing the uses goes, what it mean a good idea to used mash to join the 2 pieces in you setting up blue it together? Something like durabond.

 

I used my voice command to type that last post and didn't proof read it. It was supposed to say as far as splicing the pieces would using mesh and durabond be a good idea? Maybe a wire mesh so it's strong and supports better?

 

I've been accused of not talking plain

Mesh tape doesn't preform as good as paper tape, when 'sticky tape' [mesh] is used it's recommended to use a setting compound like Durabond over it to 'lock' it down. IMO a wire mesh would be more trouble than it's worth. While drywall should never be considered structural, it gains a good bit of strength once the pieces are taped and finished.

 

I just realized when I cut the drywall on the exterior wall some of it but not all of it had foil backed 5/8 drywall. Is that for a vapor barrier? It was only in one room I believe.

 

The picture I posted are called "Insta-back" clips. Appears they are sold at dry suppliers, or online. I think I have also seen then at some big box stores.

 

I haven't seen foil backed drywall in years. It was used as some sort of vapor barrier and I assume it's no longer used because there are better [probably cheaper] ways to seal the wall/ceiling.

 

So now when I redo the wall do I need to seam together some kinda vapor barrier to the foil backing or should I just skip it since it's not good technology anymore?

 

I would think the foam you have between the drywall and the foundation would be sufficient.

If I remember correctly, the foil backed drywall was mostly used on ceilings with the thought that it would help reflect the heat back into the attic.

 

Makes sense I guess. I don't really know if they did try to make a vapor barrier or not cause I did see some caulk along entire perimeter of the floor. Don't know if that was for vapor barrier or not but not all the walls have the silver. Now I do have a section glued to a white painted cement wall right behind my woodstove. Would it be smart to get some kind of a vapor barrier to glue between my drywall and the cement?

 

I only have a cursory knowledge about vapor barriers and insulation. It's customary to have a vapor barrier between the drywall and the insulation. Yrs ago the paper backing on the insulation was considered good enough, now days a plastic vapor barrier is usually preferred.

 

I understand what you're saying, but I don't think it would work if I put some kind of vapor barrier behind my new drywall installation unless I somehow sealed it to the old foil. If I hired a new contractor I wonder what they would do, would they go through all the work of installing a new vapor barrier or just put up the new drywall and call it a day.

 

Unless you can caulk or tape in a patch piece of vapor barrier, I'd opt to forget it.

 

Around here Instabacks are called "bullfrogs" If you have those little clips facing down and have a stack of a few to ten clips they look like a frog sitting there.

 

Ok thanks for the replies. I think I'm going to just forget the vapor barrier repair. I figured since it didn't have a plastic sheeting type barrier to begin with, it couldn't have been that effective from the start, right? It just had the silver backing and caulking where wall met the floor. Would it be a good idea to cut a hole in the wall and pull back the new drywall in a year to check for mold growth or anything rotting? Will I need to use a dehumidifier in the basement from now on?

 

Hello I'm back again. I am going to start to fill in my gaps between drywall repair pieces with the durable soon. I have a question about taping. Do I fill the gap with the durabond and smooth and let it dry, then mud and tape over it as if there was never a huge gap or do I fill with the durabond then tape while durabond is still wet using it like mud and go that way. Also is it definitely better to fill the large gaps with durabond instead of expandable foam?

Thanks again guys

 

It's best to prefill the gaps and let it dry before taping. You can cheat a little when using a setting compound like Durabond but you still want it to be set up and more or less dry to the touch. I've never used expandable foam with drywall work ..... a pic or two might help us better understand the gaps you are dealing with.

 

Finally, heres some pictures of the gaps. is this gauranteed to crack in the future?

 

If you prefill the gap [and let it dry] then use paper tape it should be ok. The biggest issue is getting the prefill mud to stay in the gap, it might take 2 coats. It's ok to have small voids in the gap as long as you aren't relying on the tape alone to give that section of the wall strength.