# cleaning up foundation walls for good foam board adhesion



## strategery

Would it be a mistake to use a pressure washer to try to get the old chipping paint and debris off of my basement walls? I want the foam board to have a really good adhesion. I worry that the glue alone will not be strong enough.

I was told by a friend that I will regret bringing a pressure washer down there because water will get between the walls and will take forever to dry (I don't have a sump pump) even with a dehumidifier running.

In some areas the wall looks like it's bowing in a little but it is in fact the paint bubbling off. Some of the paint chips off easily with a putty knife. Most of it doesn't come off so easily. It's a lot of work.

What do you think?


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## Canucker

Get a wire brush and start scrubbing. Pressure washer is just a bad idea, if you want to see the results, open the door to your bathroom, run hot water to the shower till the tank empties without the fan on. Multiply by 10. that's what the pressure washer will do to your basement and house. 
Once you glue the board to your walls, you need to mechanically attach it as well. Either build a stud wall against it or attach strapping through it and secure it to the concrete wall. Pressure washers are for outside.


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## Windows on Wash

+1

Good stiff bristle brush and start hitting the walls with it.

You will be surprised how well the adhesives will bond as they will grab the irregular surfaces and hold the board to it.

You will need a mechanical bond as Canucker mentioned too.


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## algored2deth

Also make sure the paint does not have lead in it. Maybe you have checked but if not, do so. It will change your strategy here. Otherwise, the other's ideas are good starting points.


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## strategery

Thanks for the help, guys. I will go to home improvement store and pick up a brush tonight. Hoping to get this project done and have the insulation up before december.

One more question. I don't know much about the mechanical fastening aspect of this job. What kind of strips do I need to be looking for that will be good to work with? Is there something specific I need to ask for or use?


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## aejamison

I used masonry nails with large washers, then taped over the nail/washer when done with foil tape. I had to use a 2lb hammer to drive them in.


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## TimMauriello

Do you plan on framing walls in front of the foam board? If so, if you frame tight to the insulation you'll be fine and wont need to screw or hammer it in.

If not, you now have another issue as foam board isn't supposed to be left exposed as its a fire hazard. You'd have to look into local codes on that. If its for a mostly unused space, you are probably safe, just could have inspection issues down the road...


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## aejamison

Or you could use Thermax - foil faced, so it doesn't need to be covered if basement is to be let unfinished.


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## strategery

Well, guys, my situation isn't looking too good right now.

I bought a wire brush a week ago and started cleaning up the walls as best I could. It's really a tough job.

I started in a small area and I attempted to glue a half inch foam board to the wall and I just can't get it to adhere. I used a foam board adhesive glue applied by a caulk gun and I used the entire tube just trying to get a small area to stick. No luck. I tried pressing hard against it and leaning against it but it's not working.

What would be the next best bet? Do I need to drill some pilot holes then drive some masonry nails through the wall to get it to stay?


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## Windows on Wash

sounds like a 2 person job now.

Hold the insulation up, hammer drill, and screw the 1x4 sleepers through the foam into the wall with masonry screws.


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## joecaption

What is it your really trying to achieve with this project? If your looking for a finished basement then there's far simpler ways to do it.
Just build a wall at least 1/2" away from the outside wall using pressure treated lumber as the bottom plate and insulate with fiberglass made just for basements.
Two reasons paint comes off basement walls, wrong paint, moisture coming in from outside.
If the basement damp then trying to do anything on the inside will fail.
It needs to be addressed from the outside first.
Working gutters with down spouts far away from the foundation.
A french drain.
No flower or mulch beds up againt the foundation.
Grade slopes away from the house.


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## strategery

Not trying to finish it, just insulate the walls for improved comfort and to prevent energy loss.

Can't finish the basement because not enough clearance.


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## TimMauriello

Then you may get the most bang for your buck just insulating the rim joists area.

But, to hold the foam up, you could just put a pt 2x4 on the floor to hold a tight, slip the foam in behind that, than screw a 2x4 right in front of it at the top right into the joists to hold it in. Basically just the bottom and top plat of a wall.


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## strategery

Windows on Wash said:


> sounds like a 2 person job now.
> 
> Hold the insulation up, hammer drill, and screw the 1x4 sleepers through the foam into the wall with masonry screws.


When I drive the masonry screws through the foamboard and into the foundation wall (red clay block), do I want to drive through at the mortar line? Someone suggested I do that to avoid cracking the brick.


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## cbaur88

That might be a good tip but I think by pre-drilling the holes will eliminate most of that threat. 

I'll be doing the same thing soon, however my wall foundation in my crawl space is cinder block w/ no paint to worry about. I am researching the best way to adhere the foam board to my walls as well. I don't see adhesive working that great simply because my walls are not flush flat and they might be too cold. There is excess mortal sticking out in many spots. I suppose I can chip that off but would like to get the best adhesion possible but need advice on what types of screws, nails, sinkers, etc... to use.


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## strategery

Have you already bought the foam board insulation? If not, maybe you could get a more flexible 1 inch board or 1/2 inch.

In my case, I had to insulate to R-12 in order to get utility company rebate. So I bought 2 inch boards and 1/2 inch board. I'll go around the walls first with the 1/2 inch board because it's more flexible. Then I will attach the the 2 inch to that.


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## cbaur88

strategery said:


> Have you already bought the foam board insulation? If not, maybe you could get a more flexible 1 inch board or 1/2 inch.
> 
> In my case, I had to insulate to R-12 in order to get utility company rebate. So I bought 2 inch boards and 1/2 inch board. I'll go around the walls first with the 1/2 inch board because it's more flexible. Then I will attach the the 2 inch to that.


I haven't just yet. I bought 2 inch foam (XPS) board and been using to it to seal the rim joists. So far it's made a nice difference in stopping the airflow into the crawl. I am also using to seal up the three vents I have down there. I did one last night and seemed to really stop the air flow. That's a good idea with using the 1/2 inch flexible first, might just have to try that. Thanks!


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## Daimer

Cleaning foam adhesive walls with pressure washers are really a bad idea. You need to contact a good cleaning services provider.

Thankshttp://www.daimer.com/pressure-washers/


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## strategery

Anyone have an opinion whether I should glue and fasten the 1/2 inch and 2 inch boards together into the wall? Or should I only fasten the 1/2 inch into the wall then glue the 2 inch on top of that?


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## cbaur88

strategery said:


> Anyone have an opinion whether I should glue and fasten the 1/2 inch and 2 inch boards together into the wall? Or should I only fasten the 1/2 inch into the wall then glue the 2 inch on top of that?


I would think if you glue and fasten the 1/2 inch to the foundation wall you would be fine to simply glue the 2" foam board to that. From what I hear that foam board adhesion is pretty bonding stuff and I think you'd get an exceptional bond when going to foam to foam because it's dry, clean and smooth vs. the foundation wall possible having moisture, dirty, rough and non smooth surface. 

I am going to try and use PL-300 adhesive directly to the wall with 2" foam. I'll try it and see how well it holds up. If not I'll be using some type of anchor to the foundation wall as well but hopefully I can save some work and just use the adhesive. Good luck! :thumbsup:


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## algored2deth

TimMauriello said:


> But, to hold the foam up, you could just put a pt 2x4 on the floor to hold a tight, slip the foam in behind that, than screw a 2x4 right in front of it at the top right into the joists to hold it in. Basically just the bottom and top plat of a wall.



I was curious if you considered this idea by Tim here? I think this is the way to go. Effectively you do build a wall but you will get the chance to put drywall in front of the foam for fire protection.


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## cleveman

Interior or exterior of wall?


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## benjamincall

cbaur88 said:


> I would think if you glue and fasten the 1/2 inch to the foundation wall you would be fine to simply glue the 2" foam board to that. From what I hear that foam board adhesion is pretty bonding stuff and I think you'd get an exceptional bond when going to foam to foam because it's dry, clean and smooth vs. the foundation wall possible having moisture, dirty, rough and non smooth surface.
> 
> I am going to try and use PL-300 adhesive directly to the wall with 2" foam. I'll try it and see how well it holds up. If not I'll be using some type of anchor to the foundation wall as well but hopefully I can save some work and just use the adhesive. Good luck! :thumbsup:


You should have no trouble bonding the 2" foam to the 1/2" foam. The PL300 creates a very strong bond. I've used the stuff to bond XPS to itself. I would just be sure to brace the foam while it's curing. You should stagger the seams of the 2" and the 1/2".

Here's what I did for my project:

1. I roughed up the surface of the paint using a disc grinder and a paint stripper type disc.

2. I put down a lbead of PL-300

3. I ran several tapcons with fender washers into 2" foam, adding extra fasteners where irregularities in the wall made the foam pull away.

4. I sealed the seams between the sheets and at the top of the foam panels using PL-300.

5. (haven't started yet) Run Tyvek tape over the seams, just for good measure (it's cheap, right?).

6. Glue a strip of foam on top of the block wall

7. Remove the tapcons in the wall, filling the hole with PL300

8. Use PL300 to adhere a second layer of 2" foam to the first layer, bracing with 2x lumber.

9. Frame the wall right against the foam.

10. Fill the stud bays with Roxul


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## strategery

I went to the big box store to pick up some tapcons to fasten the 1/2 board to the wall and I asked for advice on what size to get. He told me that drilling into red clay block foundation is a mistake and it would break.


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## benjamincall

You mean you have a terra cotta block foundation? I would experiment with different wood screws and forget about using a hammer drill. I haven't worked with terra cotta, but I have had some success using small wood screws to secure cable clips directly to crumbly stucco. If you can't find a screw that works to your satisfaction, I would just apply the adhesive and brace the heck out of the panel. I would use small squares of plywood and 2x lumber with bags of concrete or olympic weight plates piled on top.

P.S.
I wouldn't go longer than 1" on those screws.


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## strategery

I honestly don't know if that's what it is. It's a red brick with crumbling mortar. It's got some white coating on it that I have been trying to scrape off.


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## benjamincall

Is the brick hollow? If the white coating is cementitious, I would just bond the XPS to the coating.


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## strategery

I'm not sure if it's hollow. I think so but I'm not for sure. It's lasted all these years (built 1919) so I'd think if it were an inferior foundation it wouldn't have lasted this long.

Also, there are no footings underneath the walls. I checked and I've asked others to tell me if it has footings. They got out this flexible rod and poked underneath there and found no footings.

EDIT: Ok, it does appear to be terra cotta. I googled a bunch of pictures and I see the same grooves in the block that I see in mine when I scrape off the white coating.

Does that mean drilling in it is not an option since it's brittle? I'd sure like to get that foam board to adhere to the walls but it won't stick.


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## cbaur88

benjamincall said:


> You should have no trouble bonding the 2" foam to the 1/2" foam. The PL300 creates a very strong bond. I've used the stuff to bond XPS to itself. I would just be sure to brace the foam while it's curing. You should stagger the seams of the 2" and the 1/2".
> 
> Here's what I did for my project:
> 
> 1. I roughed up the surface of the paint using a disc grinder and a paint stripper type disc.
> 
> 2. I put down a lbead of PL-300
> 
> 3. I ran several tapcons with fender washers into 2" foam, adding extra fasteners where irregularities in the wall made the foam pull away.
> 
> 4. I sealed the seams between the sheets and at the top of the foam panels using PL-300.
> 
> 5. (haven't started yet) Run Tyvek tape over the seams, just for good measure (it's cheap, right?).
> 
> 6. Glue a strip of foam on top of the block wall
> 
> 7. Remove the tapcons in the wall, filling the hole with PL300
> 
> 8. Use PL300 to adhere a second layer of 2" foam to the first layer, bracing with 2x lumber.
> 
> 9. Frame the wall right against the foam.
> 
> 10. Fill the stud bays with Roxul



I did very similar for my crawl space project but used different anchors "Red Head" as I had no luck with the tapcon anchors holding. It could have been I used them wrong, who knows. The Red Head anchors worked amazingly and were very simple to use. I bought over sized washers to secure the foam more to the foundation wall. I only used maybe a dozen of these in various spots as the PL-300 held very well for me but the area's the wall was out of whack or didn't get a good seal or was loose I used an anchor. I stayed away from the Tyvek Tape for the joints as I read on another forum the manufacture says to only use with Tyvek Vapor barrier and not on foam. I have heard it does not hold up well over time and will fall off but who knows for certain so to be safe I used Foil tape instead. I also used Roxul in my stud bays.


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## benjamincall

strategery said:


> I'm not sure if it's hollow. I think so but I'm not for sure. It's lasted all these years (built 1919) so I'd think if it were an inferior foundation it wouldn't have lasted this long.
> 
> Also, there are no footings underneath the walls. I checked and I've asked others to tell me if it has footings. They got out this flexible rod and poked underneath there and found no footings.
> 
> EDIT: Ok, it does appear to be terra cotta. I googled a bunch of pictures and I see the same grooves in the block that I see in mine when I scrape off the white coating.
> 
> Does that mean drilling in it is not an option since it's brittle? I'd sure like to get that foam board to adhere to the walls but it won't stick.


I'd simply experiment with a couple of different fasteners. You won't need to put a lot of torque on them. You can buy a box of eight 3/16" x 1-1/4" hex head Tapcons for $2.75 at Lowe's. A 5/32" masonry bit costs about $2.50. I would not feel the need to embed the screws a full inch. Just run them in until they pull the foam snugly to the wall. You can probably get the Tapcons to do the trick if you avoid using hammer mode to drill your pilot hole and if you drive your screws slowly. You might try the Red Head brand fasteners, as suggested.


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