plasterboard tape

[DNL]

I was told on the weekend I should only use paper tape for jointing the plasterboard sheets for wet areas over sink.

I've checked out www.how2plaster.com (great site by the way) and the issue of paper versus fibreglass only appears to be an issue for ceilings - ie: only use paper on ceilings and for butt joints.

I am looking to join the blue board sheet to the gyprock sheet on the wall where sink will be, this will then be tiled over so is there an issue using paper v fibreglass tape on the sink wall?

Also, should I look to seal the sheets with an undercoat prior to tiling over for sink area and splashback? If so, is normal undercoat ok to use?

cheers

[mic-d]

I was told on the weekend I should only use paper tape for jointing the plasterboard sheets for wet areas over sink.

I've checked out www.how2plaster.com (great site by the way) and the issue of paper versus fibreglass only appears to be an issue for ceilings - ie: only use paper on ceilings and for butt joints.

I am looking to join the blue board sheet to the gyprock sheet on the wall where sink will be, this will then be tiled over so is there an issue using paper v fibreglass tape on the sink wall?

Also, should I look to seal the sheets with an undercoat prior to tiling over for sink area and splashback? If so, is normal undercoat ok to use?

cheers

You don't need to joint under areas to be tiled and in fact plaster products under tiling should be avoided since the tile adhesive won't stick. If you have recessed edges you can screed them flat with some flexible cement-based tile adhesive. Next day put the tiles up with a mastic adhesive such as Ardex D2. priming may be needed depending on adhesivee instructions. D2 just needs a wipe to remove dust.

Cheers
Michael

[DNL]

Thanks Michael - in fact that will save me a lot of work as of the three new walls in the kitchen, two will be tiled where the joints are exposed. Only one wall will not be tiled but this will have a pantry and fridge covering the bulk of the wall.

When you say a "flexible cement based tile adhesive" what would be a good recommendation?

I will still have the lounge area to look after for joint filling, but no tiling so the problem - or at least the theoretical side of the problem - is solved!

cheers
Dave

[rod@plasterbrok]

Using paper tape and basecoat only for tiled areas such as showers and bathrooms is an acredited method of wet area plasterboard installation.

ALL plasterboard joints MUST be taped under tiles. The Boral acredited system uses wet area taping cement which is an acrylic taping cement used in conjunction with paper tape. Other systems also acredited, use basecoat and papertape.

However for a splashback over a kitchen sink I would not be too concerned with the tape used. The most important point is that you do not use top coat where tiles are to be used and that you DO actually tape the join. It is top coat that is a problem in tiled areas. The reason paper tape is the recomended tape, is that it is the stronger tape less prone to cracking, NO TAPE will be asking for trouble.

Tiles will actually stick to top coat, however the problem is if water gets in behind the tiles the top coat will turn back to its wet form and the tiles will let go. This does not occur with basecoat. This rule is a precaution against the failure of the grout and wet seal.

All showers should be tanked with one of many available wet seal agents.

Cheers Rod

PS. I will get around to updating my site to include information on wet area installation.

[ausdesign]

excellent info & explanation Rod.

[Barry_White]

Rod

Where were you 28 years ago when I did my place. I was told by a plasterer to use the nylon tape because it was easier to use and just use top coat and allow it to set between coats. (So much for professional advise). In my wet areas I did the same now apart from one small area above a basin where the tiles have a hairline crack along the horizontal joint all other areas including the showers are fine but it concerns me that the cement could break down.

BTW I did my own tiling and they are very well grouted.

[DNL]

Rod - thanks for the advice mate. I think I will tape, no offence Michael, but the beauty of two points of view is I now have options!

When I removed the tiles off the old walls, there was a fibro cement sheet on top of the plasterboard. I must admit though, the tiles came off without too much issue due to long term water seepage.

The simple solution may be glass splashback!! But I'm sure a reality check on price will swing me back to tiles.

Bottom line gents - thanks for the input. It has given me the info requried.

cheers
DNL

[mic-d]

Using paper tape and basecoat only for tiled areas such as showers and bathrooms is an acredited method of wet area plasterboard installation.

ALL plasterboard joints MUST be taped under tiles. The Boral acredited system uses wet area taping cement which is an acrylic taping cement used in conjunction with paper tape. Other systems also acredited, use basecoat and papertape.

However for a splashback over a kitchen sink I would not be too concerned with the tape used. The most important point is that you do not use top coat where tiles are to be used and that you DO actually tape the join. It is top coat that is a problem in tiled areas. The reason paper tape is the recomended tape, is that it is the stronger tape less prone to cracking, NO TAPE will be asking for trouble.

Tiles will actually stick to top coat, however the problem is if water gets in behind the tiles the top coat will turn back to its wet form and the tiles will let go. This does not occur with basecoat. This rule is a precaution against the failure of the grout and wet seal.

All showers should be tanked with one of many available wet seal agents.

Cheers Rod

PS. I will get around to updating my site to include information on wet area installation.

Geez Rod, am I going to have to admit I'm wrong? !!

Certainly don't agree that tiles stick OK to topcoat until its wet. I've pulled enough tiles myself and read/spoken to others to know that it just doesn't. Tiles may not ever fall off, but stick a scraper under it and pop, off it comes.
I can understand the use of tape under areas to be painted where fine cracks might marr the paint, but under tiles? I know you will say it is the way its written, but then they say you can use hmr plasterboard in showers
OK, it can't hurt, but what trouble are you looking for if you don't tape? How will it cause the tiles to fail? If the joint moves so much that modern tile adhesives fail then there are serious issues with the fastening of the sheet. If you've fastened the sheeting correctly for tiled applications, what chance of failure, that taping helps.

Cheers
Michael

[rod@plasterbrok]

Michael, it is not a matter of being wrong rather than being missinformed we can all be missinformed on issues.

I certainly do not endorse tiling over top coat in any condition for any reason. The point I was making is that even though they will "stick" to top coat they should not be.

Joins in plasterboard that are not taped will crack 100% of the time. The tile can and will crack at that weak point, I have seen this myself and Barry's post above confirms that. The tiles wont crack in every case but often enough to say it should never be done without taping. If all jobs were done without taping the join there would be claims by 100's of home owners for faulty workmanship.

The manufacturers of both the tiles and the plasterboard/villaboard would run a mile and not cover the products with warranty. It is "written" because it is required.

If you are spending a great deal of money on a bathroom the cost of taping the joins with paper tape is negligible vs the cost to make a repair in the event of failure. It is just not worth the risk. If you did one house a year you may never have a problem but the one house you do may fail, is it worth it?

It is not a case of the board not being fixed properly or not, it will crack in time, regardless of how the board is fixed.

Wet area plasterboard is fine to use as a lining in showers provided that it is installed correctly. It is an accredited system and has been thoroughly tested and approved.

When I built my own home I had the choice of wet area plasterboard or villaboard provide to me free of charge by our suppliers. I chose the wet area plasterboard for several reasons, all pretty much on personal preference rather than performance. We sell and install both villaboard and wet are plasterboard every day based on the preference of the builder.

I prefer the consistency of the paper face liner board, the surface of villaboard can look ordinary under certain lighting conditions. Having a consistent thickness makes it easier with door and widow frames. Also plasterboard comes up straighter if there are framing iregularities and it is easier to install. These are just my personal preferences.

We did a test on plasterboard and villaboard years ago, where we made a box out of each and filled it with water. The dampness came throught the villaboard before the plasterboard! Having said that though even though villaboard will soak up moisture quick it will not deteriorate as quick as plasterboard under consistant wet conditions.

My theory on that is that I would prefer to know I have a problem and get it fixed before the framing rots!

I hope this helps and is not too long winded.

Cheers Rod

[DNL]

Also, should I look to seal the sheets with an undercoat prior to tiling over for sink area and splashback? If so, is normal undercoat ok to use?

cheers

Now to the second part of my question?

What i am intending on doing is tape all joints (both vertical internals and horizontals) with fibreglass tape, use base coat only in horizontal joints and the system on internal corners as seen on Rod's site

Give the wall area an undercoat all over, and use a solvent based paint only on the area to be tiled.

Looking last night at the construction guidelines - I have placed screws every 300mm on vertical studs only - looks like I need them at 150 centres. Glue has been put on 200 from all edges and at 230 intervals - but I might have been a bit keen in some areas using too much and maybe too close.

What are the issues with a screw through glue?

cheers
Dave

[rod@plasterbrok]

Dave You only have to nail at 150 centers directly behind the tiles ONLY. Glue should NOT be used where tiling.

Internal corners should be taped with paper tape only.

If you screw through the glue it is quite likely you will get popped nail heads. Which is a crack around the head of the nail.

See the thread below on popped nails. They can be easily repaired but means painting the wall again some time down the track.

Cheers Rod

[DNL]

Thanks Rod

Well...I started the plastering tonight. 1st wall is little rough, but I put that down to watching how the product, jointing knife and wall interact.

I've erred on the side of caution and only put a thin layer in the recess only - at this stage I can still see the join and some of the tape in patches, but I expect I will cover that once the second covering of base coat goes on.

The positive - the second wall is better!! And it is not as hard as what I thought. While I am trying to adhere to the sanding is the enemy scraping is the friend theory, at the end of the day, I can sand to ensure I have a smooth wall.

By the way...too late for glue behind the tile area!It's already done!

cheers
Dave

[rod@plasterbrok]

Good luck with it Dave. sounds like you are doing the right things.

[DNL]

It is going very well actually - as I keep saying, Rod, your site is briliant and it has been invaluable for the tips of the trade.

I've measured up tonight and wouldn't you know it, there is one line of screws which will be covered by tiles. I was out by 12mm - so these heads sit just above the bench top.

Should I remove these screws and bog the holes or sink them in well below the surface and bog and risk manage?

regards
Dave

[rod@plasterbrok]

If you take them out you will eliminate the chance of popped heads. I am assuming you have glued the sheet per the post above.

Screwing them in too deep, is not a good idea.

Cheers Rod




Cheers