bathroom job advice

[cam_low]

A while back I asked a question about the weight issue. Now I told the customer to change their tiles as they were sold porcelain 25kg/m2 tiles which were to be fixed onto a skim over blocks.

It has come back to haunt me with the cusomter now saying they want to keep the tiles...

So where do I go from here, Yorkshire tiles have recommended fixing hardi backer boards.
How would I fix these to the walls ? Would I have to remove the skim?
Any other issues ?

I have advised to reboard the whole room as the tiles are only going one metre.
Should the hardi boards be fitted over the skim and the tiles are then fixed there will be a sizable ledge and imo leaving the finish crap.

Could I tile straight onto what is presumably breeze blocks after priming ?

grrrr what a life

thanks people.

 

[Dave Ramsden]

Hmm tough one. Im not "up" on this backer board stuff but I would recommend some sort of material to line the wall with to give it some strength. You can silicone of liquid nails the back the screw it up with the correct length screw and some penny washers. I dont think you have to prime backer board before tiling but I would use a flexi rapid addy and a flexi grout also.
As for finishing off, you could get some deeper trim and fix it to the back of the backer board so it covers the depth difference.
Post some pics when you get finished bud!

 

[cam_low]

deeper trim ?

is this available ?

any at ctd ?

 

[DHTiling]

When fixing ceramic wall tiles to gypsum plaster surfaces on masonry backgrounds you should keep the following points in mind:

1. Although ceramic tiles can be fixed to a wide variety of backgrounds with appropriate adhesives, most tiling is fixed onto cement-sand rendering, gypsum plaster systems or onto plasterboard.
2. Cement-sand rendering is the preferred background for tiling and detailed guidance is provided in British Standard Code of Practice BS5385 Wall Tiling (BS5385-1, BS5385-2 and BS5385-4). Less information is provided about gypsum plaster backgrounds and this joint statement has been prepared in order to emphasise the conditions under which gypsum plaster can be safely used as a suitable background for ceramic tiles.
3. It is very important that the masonry background is thoroughly dry. A minimum of six weeks should have been allowed between the construction of the masonry background and plastering. The presence of moisture in the background will not always be visually evident.
4. This is particularly important where gypsum plastering is to be applied onto concrete walls especially if of lightweight or aircrete (aerated concrete) blocks or onto insitu concrete walls or onto cement-sand rendering.
5. Caution: Cement-sand rendering dries gradually with shrinkage taking place. If a cement-sand undercoat is not cured and dried prior to plastering and tiling, the subsequent drying shrinkage of the rendering can break the adhesion between the undercoat and finish coat of gypsum or between the finish and tile adhesive causing failure. New concrete walls require a longer drying time to allow shrinkage to take place, otherwise similar problems will occur. The same is true of existing concrete walls which have become saturated in use.
6. If plastered or rendered walls are to be tiled, this should be decided in advance of plastering, and should be given as a separate item in the Bill of Quantities and contract specification. See item 19.
7. Plastering should be done in accordance with the recommendations given in BS5492 and modified in BS 5385-1 section 3.4. The plasterwork should be firmly adhered to its background and be sufficiently strong to support the specified tiling.
8. The maximum weight of tiling which can be supported by a dry, well-adhered plaster background is 20kg/m2, generally equivalent to ceramic tiles with a thickness of 8mm or natural stone tiles with a thickness of 7mm. When fixing directly to unskimmed paper-faced plasterboard surfaces the maximum permissible weight is increased to 32 kg/m2. These weights include adhesive and grout.
9. Proprietary gypsum based systems are recommended because both the undercoat and finish are designed to work together. Advice on which finish coats work with which undercoats is available from the manufacturers.
10. Gypsum plaster must be thoroughly dry before tiling. New plasterwork consisting of undercoat and finish coat should have been completed at least 4 weeks before tiling is commenced. Tiles should never be fixed to plaster which is not dry throughout. Where drying is assisted by space heating or dehumidifying, care should be taken to ensure that the plaster is not just dry at the surface. The heater or dehumidifier must not be directed at the plasterwork.
11. It is important to understand that some gypsum plasters may appear dry on the surface whilst still containing moisture within.
12. Use of non-invasive radio frequency moisture meters will be of help in determining moisture levels still within rendering/plastering and/or the background.
13. When it is known in advance that tiles are to be fixed to a plastered wall, it is essential that there should be good adhesion between the undercoat and the plaster finish coat. Tiles should only be fixed to the finish coat and must not be fixed directly to a gypsum undercoat.
14. The finish plaster should be specified and applied to provide a matt finish. Excessive trowelling of the plaster to ‘improve’ its appearance must be discouraged, since this practice may result in a dusty or shiny surface which is not suitable for tiling. If the finish plaster is hard and sound but has dusty or friable residues on its surface, the surface should be thoroughly brushed down. If trowelling of the surface has produced a shiny and smooth surface, this must be removed by vigorous brushing. Where the use of a primer is recommended before the tiles are fixed the recommended primer should be applied strictly in accordance with the manufacturer’s instructions.
15. Every plaster surface should be examined carefully by the tile fixer before any tiling work is undertaken, paying particular attention to surface finish. In addition, it is important to sound the whole area carefully for any evidence of hollowness or lack of complete adhesion in the backing. Any such defects must be remedied by cutting out and replastering before tiling. The repair must also be allowed to fully dry out.
16. On old plastered surfaces any decaying or loose areas must be cut out and made good.
17. Sometime painted plaster surfaces are encountered. Hard gloss paint if well bonded is usually a satisfactory base for tiling, but any paint showing signs of flaking should be removed. Emulsion paint or distempers can break down after tiling and must be removed mechanically prior to tiling. The surface to receive the tiles must be clean, sound and dry.
18. Since thin-bed adhesives not exceeding 3mm bed thickness are generally specified for fixing tiles to plaster, the plaster surface should be plumb, true and level. Trueness of surface should be such that when checked with a 2m straightedge, any gap between points of contact should not exceed 3mm. Note: However such close tolerances of the trueness of a plastered surface will not have been attained unless the surface was specified to be tiled prior to plastering and the appropriate specification for plasterwork defined. Explanation a plastered surface, which is not to be tiled, is not required to meet such tolerances.
19. Generally, ready mixed adhesives conforming to Types D1 or D2 of BS EN 12004 are appropriate for fixing ceramic tiles to properly prepared plaster backgrounds.
20. Where fully vitrified large format tiles (under 20kg/m2) are to be fixed the recommendations from the adhesive manufacturer regarding adhesive and surface preparation should be sought.
21. Plaster is not a satisfactory base for tiling in wet areas e.g. shower compartments. Reference should be made to BS5385-4 for tiling in wet areas. If the backing consists of existing gypsum plaster seek the adhesive manufacturers advice on suitable waterproofing systems.

Tiling to Gypsum Plaster

 

[DHTiling]

The maximum weight of tiling which can be supported by a dry, well-adhered plaster background is 20kg/m². This is equivalent to ceramic tiles with a maximum thickness of 8mm plus tile adhesive or natural stone tiles with a maximum thickness of 7mm plus tile adhesive
The weight of tiling to a plasterboard background direct (without plaster skim) should not exceed 32kg/m². This is equivalent to a ceramic tile and adhesive with a maximum thickness of 12.5mm and natural stone and adhesive with a maximum thickness of 10mm.
It is important to emphasise that the weights quoted includes both the tile and adhesive.
Further advice should be sought either from the manufacturer, regarding the suitability of the adhesives and grouts and also guidance must be sought from board manufacturer regarding additional information on recommended methods for the installation of boards.
The following table offers general guidance to some common types of building board and the maximum recommended weights for tiling.




Gypsum Plaster 20Kg/m²

Gypsum Plasterboard Direct (without a plaster skim) 32Kg/m²

Plywood (WBP) Up to 30Kg/m²

Lightweight Tilebacking Boards* Up to 40Kg/m². Dependant upon the type and thickness of the board.

Glass reinforced Cement Sheets Up to 50kg/m², Dependant upon the type and thickness of the board.

Gypsum Fibre boards Approximately 35- 40Kg/m²


http://www.tiles.org.uk/help/answer-weight.shtml

 

[cam_low]

thanks for all that dave but im more after an opinion of what to do with the situation?

thanks

 

[DHTiling]

Hi Boosha......Quickest way is to chop all the plaster off and dry line the room with 12.5mm plasterboard.....with those tiles that will allow for adhesive and grout as well......


I posted that other info for other readers as well.......

 

[cam_low]

ok, so do you think i should get a plasterer in to dry line the room as ive never done it before thanks

 

[DHTiling]

If you are not confident to do it then yes.....it's not hard to do...but you do want them flat....

I can give you a number for up your way if you require one...

 

[cam_low]

cheers dave. i have a man for the job

 

[actiling]

hi boosha,
if your going to take the skim off back to the block then you dont have to board the room out.when the skim is off,prime the area and let it dry.use a powder based flexible cement adhesive (pci is good)for the tiling.with a flat trowel bring a tight coat of adhesive onto the blocks and let it dry.tile from the bottom upwards, butter the wall and the back of the tile and let every second course dry out.i am fixing 12mm 80x40 porcelain lengthways on a job now and i stick two courses a day,looks really nice.
i have used this method for fixing heavy tiles for about 12 years and have had no problems with it.
seasonal greetings
chris.

 

[doug boardley]

Boosha, what base coat is under the skim, is it sand and cement or a gypsum base coat (ie browning, bonding). my way of dealing with this situation would be to strip all the skim below your 1 metre datum and if its sand and cement base coat you're ok for weight issues

 

[cam_low]

As the house is quite old, what should I do if there is natural stone block work below the plaster skim and not the usual breeze blocks.

 

[shane176]

i would go with ACTiling on this one geez!

 

[cam_low]

just found out that behind the plaster are red brick walls.

 

[doug boardley]

but what's between the red brick and the final plaster (skim) coat, is it sand and cement? it can't be skim straight onto red brick!:dizzy2:

 

[White Room]

Probably a standard london brick, All quality bricks were used on the external front of the house

 

[doug boardley]

Probably a standard london brick, All quality bricks were used on the external front of the house

was wondering what base coat whitebeam, and could skim coat be removed to tile onto,hopefully, sand and cement:ninja:

 

[cam_low]

well im going round to the job in the morning hopefully to take off the skim and hoping that there is a sand cement base coat. He said he got the screwdriver through it no bother to around 5/8 of an inch.

 

[White Room]

Sounds like gypsum, Would've struggled with sand/cement unless it's a really weak mix

 

[cam_low]

so if its gypsum board and i get shot of all the plaster I'll be ok to tile onto the boards?

If they are shot I could dot and dab some handy boards all the way round ?

 

[doug boardley]

what whitebeam is saying , is that it's a gypsum base coat ie browning, personally I would hack it all off and then d & d plasterboard onto brick walls. If you d&d onto existing you're just adding more weight to what could be an unstable substrate

 

[cam_low]

sorry doug that is what i actually meant too but I didnt explain it too clearly. Nor have I come across this browning. Can you tell me a bit about it please. I'll google it in the mean time thanks.

edit

broken link removed

 

[White Room]

A backing for plaster for solid backgrounds of moderate suction with an adequate mechanical key

 

[doug boardley]

It's a lightweight gypsum based base coat, designed,I think, for insulation purposes, when I was plastering mainly I hated the stuff!! hated spreading ir and hated skimming onto it! If you go in peoples living rooms where browning's been used you can usually see dents in the wall where furniture etc has damaged it.Certainly not a substrate that I would tile onto!