Frequently Asked Tiling Questions - Tile Guru


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Q. My new tiles have gone dusty and chalky after fixing. What has caused it? It looks fine when I wash it, but then goes back to looking hazy.

A. The most likely answer is that it is a grout film residue. This can happen if the if the tiles haven’t been cleaned sufficiently after grouting. Either by using a dirty sponge or the water wasn’t clean enough. When washed later, it will appear clean while still damp, but will dry cloudy again. There are solutions provided by LTP that will clean this depending on the tile. Please contact our Technical Help Line for further information.


Q. I have a newly laid screed. How long will I need to leave it to dry before I can tile it?

A. As a general guideline for cement screeds, the drying time required will depend on the thickness it has been laid. 1mm per day for the first 75mm and 0.5mm per day up to 10mm. Screeds of a thickness greater than 100mm will take considerably longer.

Anhydrite screeds dry at a similar rate. However it is very important that the screed is tested for moisture and must be <75% RH (relative humidity) or <0.5% water by weight. This can be tested using either a Digital Hygrometer or a CM tester.


Q. What does “Nominal Sizing” mean?

A. A nominal size is an approximate size that the factory will advertise for a tile. However there can be minor variations between the “Nominal” and “Working/Actual” size. For example, if a tile is shown as 200x100mm, this is the Nominal Size. However the actual working size may be 197x97mm. If you are matching up tiles or looking to use two tiles of the same Nominal Size, we’d strongly recommend ordering a sample prior to your main purchase to ensure they are suitable for your required design.


Q. Can I tile over existing floor tiles?

A. You can fix tiles over existing tiling, but first you need to check that they are firmly bonded to the substrate, then clean and degrease the tiles. Make sure a flexible adhesive is used.

If the existing tiles are loose, they will need removing and any necessary preparation will need to be done prior to the new tiles being fixed.


Q. Can I tile over existing wall tiles?

A. It is possible but you will firstly need to make sure that the substrate under the existing tile is capable of holding the weight of two layers of tiles (please see below for further guidance). Secondly you would need to make sure the existing tiles are solid and that there is no danger of them coming loose. If the existing tiles are loose, they will need removing and any necessary preparation will need to be done prior to the new tiles being fixed.


Q. Is there a weight limit when tiling a wall?

A. Yes there is. Here is a general guide to some of the most common substrates and the maximum recommended weights for tiling:

Wall Substrate Maximum Weight of tiling per m2

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 on the type and thickness of the board.

Glass reinforced Cement Sheets Up to 50Kg/m2. Dependant on the type and thickness of the board.

Gypsum Fibre Boards Approximately 35-40Kg/m2



Q. What preparation is required for newly plastered walls?

A. All new plaster must be allowed to dry for up to 3wks (dependant of thickness. This time is reduced for skims). If you are using a ceramic tile less than 300x300mm in an internal dry area, ready mixed adhesive will be fine. If the tile is larger than 300x300, porcelain or natural stone, you must prime the surface with an Acrylic Primer (such as BAL APD) and use a cement based adhesive. For wet areas such as a shower, above a bath or a wet room, the walls must be tanked first. But remember, the weight of the tile and adhesive combined, must weigh no more than 20Kg/m2. Please contact out Technical Helpline for further information.


Q. How do I cut crackle glaze tiles without the glaze chipping?

A. Firstly, we’d recommend sealing the tile with LTP Crackle Glaze Protector. This will add extra bond to the crackled glaze surface and strengthen it prior to cutting. Use a manual “score and snap” to score the surface, but don’t apply too much pressure, as the weight can damage the glaze. Two subtle scores should be enough. Drop the breaker and you should have a nice clean cut. For angled cuts, score as above, the shape you want to take out. Using an electric wet cutter, line up the blade next to the score line, on the side that is to be discarded. This should cut cleanly as your previous score lines, will act a stopper, and prevent cracks travelling onto the good side.


Q. What is an “Expansion Joint”, and do I need one?

A. An Expansion Joint (also known as movement joint) is a trim, mainly used in floor tiling. They are designed to absorb heat induced expansion, absorb vibration and allow movement due to ground settlement. They are required for any area over 40m2, where the perimeter joints are more than 10m apart. They must also be used where two different substrates meet, and are also recommended in doorways that have tiling either side.


Q. What is a Decoupling membrane, and do I need one?

A. A Decoupling membrane (or matting), protects tiles from lateral (sideways) movement in a floor. They normally have two layers, which separate as the floor moves. As an example, a tiled concrete floor starts to crack. Without the matting, the tile also cracks. With the matting, the bottom layer will stretch or split and separate from the top layer. The top layer will then bridge the crack and keep the tiles intact. The matting is recommended for use on newly laid screeds and timber floors, in underfloor heating situations and any other situation where the floor where there is any danger of movement. They are not a substitute for Expansion Joints.


Q. I enjoy DIY, but I’ve never tiled before, but how hard can it be?

A. Good tiling comes from a lot of training, years of experience, extensive knowledge, the correct equipment and a very keen attention to detail. It can be very simple to look at two identical projects and tell which one was done by an amateur or a professional. If it was easy, we’d all be professional tilers. If you insist of tackling a project yourself, do a lot of research, take your time, but at the same time, make allowances for if something goes wrong. Tiles are expensive things as would be the extra preparation when it all has to be ripped up or pulled down. Without the experience, anything can go wrong. Can you afford it if it does? TILING IS NOT EASY. So if in any doubt whatsoever, GET A PROFESSIONAL TILER IN.


Q. Do I need to have grout joints, and if so, how big should they be?

A. Yes you do. There needs to be a gap between the tiles to allow for temperature expansion and to absorb vibration. They are also essential for absorbing or repelling moisture, to prevent it reaching the substrate and causing problem behind the tile. The basic recommendations are 2mm for the wall, 3mm for the floor, unless a quarry tile or natural stone is used. We’d then recommend 5mm. However different tiles have different requirement and these sizes may vary. (Splitface Slate mosaics require butt-jointing so cannot be grouted. Therefore they are only suitable for dry areas)


Q. After laying the tiles, when should I remove the spacers?

A. If you are laying crosses in the corners, they will not need removing, providing they are sitting lower than the intended grout height (this should be almost flush with the tile face). If you are using them as pegs, they need to be removed when the adhesive has set enough to hold the tiles in place, but not set enough that they are permanently stuck in.


Q. Do quarry tiles need sealing?

A. Most quarry tiles have a very low moisture absorption rate and therefore an impregnating sealer may have very little effect. However we would recommend purchasing an impregnator as a precaution as porosity from different tiles can vary. To help maintain them, we’d recommend a surface sealer (such as LTP Iron Wax) which will prevent surface staining, enrich the look and make it easier to clean. Surface sealers are not recommended for external use.


Q. I can’t find a tile trim to colour match my tiles. What should I do?

A. If you can’t find a trim that is a close colour match, the next step is to try and match your grout colour. That way all the horizontal and vertical lines in the room will all blend in. Another option is to go for a metal trim. This will stand out and make a statement giving a more expensive look. In a bathroom or kitchen, this may also compliment your taps, sink, cooker, or any other metal fitments you have in place.


Q. Should I go for a Natural Stone or Stone Effect? Which is better?

A. There are positives to both choices. An imitation stone effect tile will have a similar look but with less maintenance requirements so may be more practical for a given situation. They may be easier to clean, harder wearing and lighter in weight to make them suitable for walls. But you will never get the same randomness, character and feel of the real thing. When treated correctly, Natural stones can still be extremely hard wearing, practical and easy to clean, but may need a small amount of maintenance to keep it looking in pristine condition. But it will be worth it.


Q. What is the difference between Granite and Quartz?

A. Granite is 100% pure natural stone, cut to size and highly polished. It is also one of the hardest wearing stones available. The Quartz however is a conglomerate stone tile. This means the quartz starts off as tiny gravel sized pieces that are then bonded and hardened together using a pigmented resin. They are then made to size and polished to give a similar look to polished granite.


Q. Do I have to use insulation boards with the underfloor heating mats?

A. No, but it is strongly recommended that you do. Without insulation, the heat from the mat will go down as well as up. Therefore a lot of the heat will be lost in your substrate. Heating the tiles to your desired temperature will take significantly longer (70 to 90 minutes) and use much more electricity to do so. With insulation, the heat is repelled upwards directly to the tiles taking only 15-30 minutes to heat, thus reducing the running costs and working more efficiently.


Q. Can I use underfloor heating on soft flooring as well as tiles?

A. Yes. For laminates, carpets and cushion flooring, a minimum of 10mm thick levelling compound must be laid on top of the heating elements before the flooring can be installed. For any soft flooring, whether it be loose laid or glued, please consult the relevant manufactures for recommendations and compatibility with an underfloor heating system before you buy.

Q. What is Tanking, and do I need it?

A. Tanking is a waterproofing system for wet areas and showers. It forms a completely waterproof barrier between the tiles and the substrate, ensuring that no moisture can penetrate the background which would inevitably cause problems in the future. It is essential for wet- rooms and showers, but please ask for advice if you are tiling any other intermittent wet areas.


Q. I have a very large tiling project to do. How do I work out what I need?

A. If you have any plans for the relevant areas, please email them to  We can assist you in working out quantities as well as advise on the correct preparations required. Please note that plans can vary from true measurements, so it is recommended that the measurements you provide are verified by your tiler before ordering.


Q. If Porcelain is impervious, why do you recommend sealing Polished Porcelain tiles?

A. When the tiles go through the polishing process at the factory, it opens up microscopic pores on the surface. Before they leave the factory they go through another process called Nano-Sealing. This is done to protect the tile in transit. But it is recommended that the LTP MPG sealer is used before grouting to top up the Nano-Sealer and ensure future protection against surface staining.


Q. What does the CE mark on a box of tiles mean?

A. The CE Mark confirms the verification by a manufacturer that these products meet required EU performance, or safety, health or environmental requirements. CE marking is a key indicator of a product's compliance with EU legislation and enables the free movement of products within the European market. 

CE marking does not indicate that a product was made in the EU, but merely states that the product is assessed before being placed on the market and thus satisfies the necessary legislative requirements and harmonised standard requirements. 


Q. How slip resistant are floor tiles? Are some more resistant than others?

A. Non slip tiles will have an R or a Group Class rating which will determine the grade of slip resistance.  Please follow This Link for further information and suggested ranges.


Q. What are the different grades of floor tiles for heavy traffic areas?

A. The PEI or Grade determines the tiles strength for certain situation. A tile without a grade number or a rating 0 is only recommended for wall use only.  But for heavy traffic, such as public areas, industrial or shop floors etc, Grade 5 are advised. Here is a table of the grades and their recommended uses. 

PEI Grade 1: No foot traffic. Wall use only in residential and commercial applications.

PEI Grade 2: Light traffic. Both wall use and bathroom floor applications.

PEI Grade 3: Light to moderate traffic. Countertops, walls, and floors for normal foot traffic.

PEI Grade 4: Moderate to heavy traffic. All residential applications as well as medium commercial and light institutional.

PEI Grade 5: Heavy to extra heavy traffic. All residential and heavy commercial and institutional foot traffic.


Q. What is a Ceramic Tile made from and how is it made?

A. The main ingredients for a ceramic tile are Clay and Sand. These materials are ground down into a fine powder, water is added and the mixture is then compressed in a mould at high pressure making the “Biscuit”. These are then dried out, primed, painted then glazed, before being fired in a kiln at approximately 1000oC.

Q. What is the difference between Ceramic and Porcelain Tiles?

A. The way they are both made is very similar. But the Clay used in porcelain (called Kaolin) is much denser than the clay used in a ceramic. With the introduction of Feldspar and being fired at temperatures up to 1400oC, this makes Porcelain much harder than ceramic.


Q. Can I clean discoloured grout line?

A. Yes you can. To clean dirty grouting on floors between tiles, use LTP Grimex. To remove mould and mildew from wall tiles, use the LTP Mouldex. Apply the solutions, scrub with a brush and rinse with clean water. Once clean and dry, we’d recommend using the LTP Grout Protector to aid against future staining and cleaning.


Q. What considerations are there when tiling in commercial food preparation areas?

A. When choosing wall tiles, they need to be practical and impervious. Natural stone is not recommended. Ceramic tiles need to be smooth and easy to clean. Floor tiles also need to be easy to clean but you may also need to consider a non-slip finish to account for spillages and cleaning. Both wall and floor tiles must be grouted with an impervious epoxy resin grout.


Q. I am about to tile a bathroom, what should I be thinking about?

A. Preparation is the most important as wet areas require tanking. You need to make sure that where water is constantly in contact on both the wall and the floor, that the background is protected from excessive moisture. Due to the amount of water present, it is also recommended that a floor tile with an anti-slip finish is chosen.


Q. What type of tiles can I use around a fireplace?

A. If the area is going to be subject to excessive heat changes whilst heating up and cooling down, we would recommend quarry tiles, natural slate or granite, or porcelain tiles. Other tiles may expand and contract to an extent that they may crack. Please contact our Technical Help department to discuss your project in more detail.


Q. Can I drill a hole in a ceramic tile?

A. Yes. Holes for brackets for toilet roll holders, towel rails, soap dishes etc, can be done easily after the tiles have been fitted. Cover where you want the hole to be with masking tape and mark where you want the hole. Using a masonry drill bit and a hammer, gently tap and chip away the glaze. Once the glaze is dented, this should be sufficient to continue drilling at a SLOW speed. Holes for water pipes need to be measured out and cut before the tile is fitted, and require a hole cutter with a centre bit.


Q. If I drop something, is it going to crack the ceramic tile?

A. Providing the tile has a fully coverage of adhesive beneath it, this should minimise the likelihood of a tile cracking due to surface impact. Small items like knives and forks, may leave a small chip on the surface, where as heavy pans may cause greater damage. No tile is guaranteed against items being dropped on them, so care should be taken in areas such as a kitchen.


Q. What is causing cracks in my floor tiles?

A. The most common cause for tiles cracking is substrate movement. On a wooden floor you may find that either the flex is too great, or there may be movement between the board joints. Concrete floors can also have movement caused by settling shrinkage or extreme changes in temperature. Wall tiles can also be affected, but in all cases, preparations can be done to prevent the possibility of this happening. Another cause for cracking is stress above voids in the adhesive where full  coverage has not been achieved.

Q. How do I fix glass tiles to walls?

A. Glass tiles are fitted in the same way as ceramic tiles. However a specific adhesive such as BAL Max-Flex Fibre is required to enhance the bond to the impervious backing. Cuts can be achieved with a normal tile cutter or an electric wet cutter with a fine blade.


Q. Once fixed, how do I maintain tiles?

A. There a many different products for the different types of tile. A universal cleaner such as the LTP Porcelain Floor Cleaner is a good all-rounder for most tile types. LTP Grimex can be use for a more intensive clean. We would also suggest the use of the LTP Grout and Tile Protector as an invisible repellent barrier to prevent staining and aid cleaning. Natural stones require regular cleaning and it is recommended that they are resealed every 2-4 years depending on usage and foot traffic. Please contact out Technical Helpline for advice in the different types of maintenance. 


Q. What are the suggested products for sealing natural tiles?

A. For polished stone such as marble and granite, use the LTP MPG Sealer. For tiles with a natural matt finish like travertine, tumbled limestone and marble, the LTP Mattstone would be the suggested product. For natural finish tiles, you also have the chance to enhance the look by using the LTP Colour Intensifier as the primary impregnating sealer to give them a richer and deeper colour.


Q. Are tiles Frost Proof?

A. Most full bodied porcelain tiles natural stone tiles are frost resistant and suitable for external use. Please follow THIS LINK for our list of suggested ranges.


Q. How long will tiles last?

A. Providing they have been fitted correctly and been given the correct maintenance, tiles will last for years and survive up until the point you decide you want to redesign.


Q. Can I install underfloor heating?

A. Underfloor heating can be used in almost any situation with any tile. However, every project will have different requirements for which you can contact our Technical Helpline for further advice.


Q. What tiling tools do I need for the job?

A. This varies depending on whether you are tiling a wall or a floor. But the basic essentials consist of; Pencil, Tape Measure, Spirit Level, Mixing Bucket, Spacers, Trowel, Tile Cutter, Grout Float and a Sponge. If you were to open up the back of a professional tilers van, you may also find Laser Levels, Straight Edges, Set Square, Knee Pads, Drills and Tile Levelling Systems.


Q. Can I tile direct onto a wooden floor?

A. Most wooden floors require bracing with either a minimum 15mm WPB Plywood, cement based tile backer board or underfloor heating insulation panels. Each screwed down at 300mm centres. This is to reduce the flex in the substrate and make a suitable surface to accept tiled flooring. Floating floors are not a recommended substrate for tiling.

Q. Can I use high gloss tiles on my kitchen countertop?

A. Most tiles including high gloss ceramics can be used. However, consideration should me made when placing pans down and cutting onto a high gloss surface. Pan rests and chopping boards should still be used to keep the tiles in good condition.


Q. How long does it take to tile a floor?

A. It depends on the area, the preparation required and the individual’s experience. What may take a Professional tiler two days, may take a DIYer significantly longer, maybe up to a whole week. It is important for anyone taking on tiling as a DIY project, to take their time


Q. What considerations should be made when starting a tiling project?

A. You need to start by assessing whether the substrate is suitable for taking your chosen tile. Preparations and requirements required may include tools, insulation, bracing, waterproofing, de-coupling membrane to cater for lateral movement, expansion joints, adhesives, primers and aftercare etc. We highly recommend contacting our Technical Helpline so that you may discuss your project from the ground up so that we can advise the best solution.


Q. What is a vitrified tile?

A. A vitrified tile is fired at an extremely high temperate to make it very hard wearing and have a moisture absorption rate of less than 0.5%, such as a Porcelain tile. A vitrified tile can be “glazed”, or “full bodied”. A glazed vitrified tile will have a base of porcelain that is then printed and glazed, giving the tile two layers. A Fully vitrified tile is a single layer that has the pigment running through the full thickness of the tile. 


Q. My grout has dried patchy. Why has this happened and how can I fix it?

A. It could either be excess adhesive that has been pushed out from behind the tile. If the is the case the grout will need raking out and reapplying.

Or, it could adding too much water to the grout mix is the most common causes of efflorescence, meaning the salt contained in the cement is dissolved and separated when water is added. When the grout is mixed, applied and starts to dry, the moisture disperses and carries the salt to the surface. It’s a very common problem with some grouts but it should be fixable.

Using the LTP Grout Stain remover, some rubber gloves and a scrubbing brush, apply the solution neat to the affected areas and scrub it for a couple of minutes. You will notice it start to fizz showing that it is having an effect. Make sure you have a bucket of clean water to hand and rinse as you are going along. After a further rinse and allowing it to dry, you should see an improvement. If the problem remains, repeat as required.

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