Dot and dabbing plasterboard with fix foam adhesive

[SparrowHawk99]

Untitled

• SparrowHawk99
• 20 Jun 2014
• 1

This ****ed up majorly.

I spent yesterday boarding the chimney and alcove and this morning came to find all the foam behind had pushed the board from the wall.

First time this has happened to me as relying on the strength of the foam alone to fill a 30mm void behind, and it's totally failed me.

I don't think even conventional plasterboard adhesive would have done the job because of the void.

Wanted to avoid battening out the wall behind but looks like it's back to square one now.

Waste of about £50 materials and an entire days work down the toilet. All the polystrene has lifted from the board so two sheets scrapped

 

[xdave]

What type of foam did you use? Did you use the correct low expansion adhesive, like Dow Insta Stik? I've used loads of cans of the stuff without any issues, including on voids greater than 30mm. It stops expanding after around two minutes and can be cut after around ten so you can be confident that it has set after lightly holding it. If your foam was still expanding after that then either you used the wrong type of foam or maybe something in the can had gone off. I haven't used drywall adhesive for years.

What did you do to prep the boards and the wall behind? It needs a good, solid background which should be misted with water immediately before applying.

 

[SparrowHawk99]

Dave I used this stuff http://www.toolstation.com/shop/Adh...ing Foam/Dry Wall Foam Fix/d180/sd2857/p60449

Don't get me wrong the foam is fine.

What I tried to do was lap the front boards you see in the picture with the ones on the side (in the alcove). So at no point was the board actually in direct contact with the wall besides that batten running through the middle, because the alcove boards stick out to much.

I left the job in a huff, and instead fitted two window soffit boards and the reveals, however I struggle with getting the boards plumb with foam adhesive.. do you have any useful tricks?

 

[xdave]

That looks like the right stuff, although I've not used that specific brand before I expect they all work very similarly. It shouldn't have expanded very much though (maybe 20-30%) - if it managed to push the boards off of the wall then maybe that brand can't be used to fill voids in one go. You may need to build it up in layers until you can fix in one go.

What I tried to do was lap the front boards you see in the picture with the ones on the side (in the alcove). So at no point was the board actually in direct contact with the wall besides that batten running through the middle, because the alcove boards stick out to much.

As long as the foam bears back onto something solid then support should not be an issue. It sets pretty hard after around 24h. I've done whole rooms where the plasterboard was never in contact with anything other than the foam and they've been fine.

I struggle with getting the boards plumb with foam adhesive.. do you have any useful tricks?

Plumb is normally fairly easy - prepare the wall so it is level (the most important step), wet both surfaces and either foam it or the board before offering it up and tapping into position. Hold it for 1-2 minutes (usually the time it takes to check everything is level) and it will be set in place. It may help to hold it up with some long levels/wood to stop the board flexing. For anything that goes against gravity I use extendible props. Fit some plastic packers (like the ones window fitters use) half in/out every six inches where you have a joint so you can lap the next sheet over them to keep them flush. Obviously it is easier with battens on the joints, but once set it should be just as firm.

 

[noseall]

Plumb is normally fairly easy - prepare the wall so it is level.

What do you mean by this?

From what I can gather foam fixing plasterboard en-masse sounds like a right faff.
Whilst it does have its plusses, the negatives kill it for me.

 

[xdave]

I mean to make sure it is flat where you will be fixing it as it makes it so much easier to bond, e.g. build up any large voids to the same depth and let them set before bonding the boards. You don't get much time with the insta stik foam to make adjustments on the fly. 'Level' was perhaps the wrong word - if it was level you probably wouldn't be boarding over it.

I find foam fixing quicker because I don't need to worry about mixing adhesive, keeping my tools clean, creating dust everywhere, or stepping backwards off a ladder into a bucket of water. It also saves my fingers from being cut to shreds by the plasterboard screws (I tried an auto-feeding driver once but didn't get on with it). The actual holding to the wall bit is not really any different to drywall adhesive - the time savings are in the other parts. The ability to line a wall and then return to the start for scrim and skimming straight away regardless of what the base wall is made of is also a bonus, plus the lack of battening or drywall adhesive helps reduce cold bridging.

 

[SparrowHawk99]

Dave I'm not understanding what you mean by preparing the wall? How exactly would you do that? Say the wall is a complete patch work quilt of differing levels, how do you actually fill voids and everything else before fix foaming?

Battening is obviously a completely different process, and in the end you can get perfectly plumb boards this way, but without battens behind I don't understand how to get the walls level pre-boarding

 

[freddiemercurystwin]

Using foam sounds like a right bodge.

 

[noseall]

Using foam sounds like a right bodge.

Not necessarily a bodge, but i'm not convinced.

We often use it when sticking to smooth surfaces like steel or foil etc.

In my opinion, it falls short in the versatility of say dry wall adhesive.

You can't point with it, repair stuff, no good for fixing beads, not much good at building up etc. As for holding the boards whilst it sets! What's that all about??

 

[xdave]

Dave I'm not understanding what you mean by preparing the wall? How exactly would you do that? Say the wall is a complete patch work quilt of differing levels, how do you actually fill voids and everything else before fix foaming?

Battening is obviously a completely different process, and in the end you can get perfectly plumb boards this way, but without battens behind I don't understand how to get the walls level pre-boarding

You can use insta stik in the same way as battens (I have not used other brands so don't know if others work in the same way). It doesn't sag and sets firm within minutes allowing you to build it up in layers if you need to. It is nothing like using normal expanding foam (that would be a bodge and very hard to get boards level) - it is a gap-filling adhesive designed solely for bonding sheets to surfaces (plasterboard, insulation, etc). A bit like gripfill but much more versatile and considerable cheaper. It is very handy for flat roofs too.

For example, if you have a wall that needs boarding but it is uneven with chunks missing, maybe an old window that was blocked up and some old plaster and bricks that have been hacked around, you could spend half an hour with an SDS chisel cutting in channel for battens, making a whole load of noise and dust, or just blitz around with the foam adhesive building up the voids where the board edges/centres will be and then by the time you get back to the start you are ready to fix the boards. Tools required: 4. The foam gun, a water mister, a long level and a knife for cutting the boards.

 

[catlad]

I have put boards up with the foam board adhesive and while it feels solid when cured it is recommended to put fixing in to finish.

 

[xdave]

With Dow's product mechanical fixings are not needed in most cases as it kind of defeats the purpose... (they state not to in the instructions).

The only time I've used secondary screws with it is for ceilings unless it is a small sheet. They're rarely needed, but it means I can reuse the props more quickly and at the end of the day the choice between fixing methods usually falls down to which is the most productive for the given task. If the end result is the same I'll choose the one that is quicker and therefore costs less - whether that is adhesive foam, screws and battens or drywall adhesive. I haven't used the latter for years though, and as far as I am aware there have not been any problems with of the boards I've installed during that time.

 

[SparrowHawk99]

Ok well I've done the whole room now.

The mistake I made was not to properly support the boards, that's why the first two I did literally just pulled off the wall - the foam didn't push them I now realize.

For anyone that says foam fixing is a bodge, well it's absolutely solid by touch, and I've checked to make sure there are no flimsy areas. As already said I wouldn't dream of foam fixing a ceiling but for walls it works perfectly well. I really hate mixing drywall adhesive in a bucket, I just avoid it where at all possible

 

[noseall]

I really hate mixing drywall adhesive in a bucket, I just avoid it where at all possible

Somebody still needs to mix a load of skim in a bucket.... .

 

[SparrowHawk99]

I really hate mixing drywall adhesive in a bucket, I just avoid it where at all possible

Somebody still needs to mix a load of skim in a bucket.... .

That's where my plasterer comes