Fixing MDF skirting foam or adhesive?

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So I need to fix mdf skirting to dot & dabbed plastered walls.

The walls should be straight but I cannot say the floors are exactly level.

Do I place the skirting right to the floor or hover it about 2mm above to remove any undulations?

To fix the skirting I am in two minds - either use foam or a polymer adhesive like Fix All or Everbuild Multistick adhesives.

As to foam should I use an expanding foam or some other specialised foam?

For about 100m of skirting - how much adhesive should I get? Box of 12?

Would adhesive / foam be enough or should I also use lost head nails? On 18mm MDF can I use 25mm nails or should I go longer?
 
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All mine is fixed with adhesive foam. Goes a long way so start with 2-3cans.Foam , allow 60 secs for expansion then place, bucket of water or full paint cans will hold in place ( (20mins or so).If you have timber floor you can brace with a scrap of timber screwed to floor.
 
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All mine is fixed with adhesive foam. Goes a long way so start with 2-3cans.Foam , allow 60 secs for expansion then place, bucket of water or full paint cans will hold in place ( (20mins or so).

I've been happy with foam too.

You should definitely use the low-expansion adhesive type, such as Dow Instastik.

However, I have found the Soudal equivalent far easier to use:

https://www.toolstation.com/soudal-genius-gun-plasterboard-adhesive-foam/p99304

You could equally use something like PinkGrip, but using a sealant gun for 100m of that, would be quite hard work!
Far easier to just press the trigger of the foam gun :)

I would also say, follow the instructions and do a test piece on some off cuts first.
You may also need some bracing against the skirting, when the foam cures; this should stop excessive expansion causing bowing.
 
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I've been happy with foam too.

You should definitely use the low-expansion adhesive type, such as Dow Instastik.
No risk of bowing .

However, I have found the Soudal equivalent far easier to use:

https://www.toolstation.com/soudal-genius-gun-plasterboard-adhesive-foam/p99304

You could equally use something like PinkGrip, but using a sealant gun for 100m of that, would be quite hard work!
Far easier to just press the trigger of the foam gun :)

I would also say, follow the instructions and do a test piece on some off cuts first.
You may also need some bracing against the skirting, when the foam cures; this should stop excessive expansion causing bowing.
No risk of bowing .
 
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So I need to fix mdf skirting to dot & dabbed plastered walls.

The walls should be straight but I cannot say the floors are exactly level.

Do I place the skirting right to the floor or hover it about 2mm above to remove any undulations?
See note below about top gaps (and wall straightness). If you were a doing it for a living you'd be expected to take out as much of the gap as you could by scribing to the floor (which in any case is a cause of draughts), if needs be by planing a bit out of the bottom of the skirting board at the bottom to get over the humps, like this shows:


As to foam should I use an expanding foam or some other specialised foam?
Use low expansion foam

Would adhesive / foam be enough or should I also use lost head nails? On 18mm MDF can I use 25mm nails or should I go longer?
A grip adhesive such as Everbuild Multistick cannot be guaranteed to hold skirtings in place until it has set - with any grip adhesive you always need some form of pin or small nail or screw to hold the skirting in place whilst the grip adhesive sets (in cold weather that can be more than 24 hours). From my limited experience foam on its' own is generally sticks with little or no need for nails. For 18mm MDF on a 12mm plasterboard wall, if you require them, you will need pins or nails at 40 to 45mm in length to ensure that you are getting a fix into the timber of the wall sole plate and/or studs. Take care not to nail where there are pipes or wires by trying to locate the studs and fix into them

Before installing check that your skirtings aren't going to project beyond the architraves

If you have any gaps at the top once you have finished this can be filled with decorators caulk, although before fixing any skirting you shoild check that the plaster isn't "kicked out" from the wall too much, because it is at the start or end of the plasterer's stroke and some plasterers are better than others at flattening this area. If it isn't flat behind where the skirting will go it can often be "adjusted" using a hammer and an old chisel or bolster to get it a bit flatter
 
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All mine is fixed with adhesive foam. Goes a long way so start with 2-3cans.Foam , allow 60 secs for expansion then place, bucket of water or full paint cans will hold in place ( (20mins or so).If you have timber floor you can brace with a scrap of timber screwed to floor.

So is it plasterboard foam I need or just any expanding foam? If it expands will it expand past the edge of the skirting?

Do I apply it in the centre or along top and bottom?
 
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So is it plasterboard foam I need or just any expanding foam? If it expands will it expand past the edge of the skirting?

Do I apply it in the centre or along top and bottom?

Basically, follow the instructions on the tin!


You can also spray a mist of water onto the substrate and board, to speed up the curing time.
 
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Basically, follow the instructions on the tin!


You can also spray a mist of water onto the substrate and board, to speed up the curing time.

How many cans would I need to put skirting up throughout a 3 bed house - about 100m of skirting and 100m of architrave.
 
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I use foam and the odd blob of polymer mastic to grab as foam has no grab
 
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I use foam and the odd blob of polymer mastic to grab as foam has no grab

Well it seems like foam is the way to go. Saying that after watching skill builder and Robin Clevit on Youtube they just use polymer grab adhesive.

I was planning to try out foam and then use weights against the skirting - then finish with a flexible acrylic cauking.

Soudals decorators caulk.

https://www.toolstation.com/soudal-decorators-caulk/p45080

or

Do I need more flexibility around the architraves which will take a bashing the way my kids close the doors!

Everbuild 195

https://www.toolstation.com/siliconised-acrylic-sealant/p28222
 
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Ordinary caulk around the architraves is normally sufficient. Remember that the architraves don't need foam or glue - in fact that tends to make for a visible gap between door linings/casings and the architraves, which is why we don't do it. If there are big gaps (i.e. more than 5 or 6mm) between the skirtings or architraves and the wall consider getting some Fossa Caulk Saver (or similar) and stuffing that in the gaps before caulking, because caulk isn't that good at bridging big gaps without additional support
 
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