How to cut and glue Ytong / Durox concrete blocks?

[AlexThePalex]

Guys, I have two questions about a small job I have to do with some Ytong blocks (dutch: cellenbeton), maybe known to some people as Durox, and wikipedia tells me in English it's called autoclaved aerated concrete. I have little experience with this type of material and lack the proper tools.

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I have to repair a plastic profile underneath a shower tub that's broken, and best option to me seems to replace it with Ytong blocks and tile it over. Unfortunately, it wasn't possible to order a new profile so I have to improvise.

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My idea is to cut 4 of these blocks so they follow the rounding and then finish it off with tiles.

So here's my first question, as always, people expect me to do these kind of jobs as economically as possible, so I was wondering what's the cheapest way to cut these blocks. I know there are saws with HM teeth for it, but buying one for just 4 blocks seems a bit overkill, and now I'm wondering if it is possible to cut them with my jigsaw and what would be the best type of blade to use.
 
Second, I need to glue the blocks to the existing tile floor, and I was wondering what the best, and again, most economical way to do this would be. I know there is special glue for these blocks, but I've heard you can also use mortar, and I was wondering if the thinset for the tiles would also work as that's a kind of mortar, isn't it? Would the blocks properly stick together and to the tiles if I used thinset?

Thanks in advance for any insight you can offer me.

 

[neeleman]

You can simply use any saw and a wood rasp like the ones from Bahco.
Because the material is so soft the saw & rasp don't even get blunt from the small task you're after.
As for glue you can use the stone glue from Illbruck. Or some PolyMax Express Glue from Bison.
Assume you already have a PUR-gun.
Sorry for the big pictures. But I always use the "picture-URL" if available.

 

[Wuffles]

Or a wet mortar mix if you fancy it. We use them in the UK for the internal walls of a cavity construction for houses and such. Any blunt hand saw will cut right through them.

 

[Nigel]

  Have you considered using Wedi board?

 

[AlexThePalex]

Neeleman and Wuffles, thanks for your answers. I have two good wood saws from Bahco, but I really don't want to use them for this. I think I'll get me a cheap woodsaw for a couple of euros, should do the trick if these blocks are so soft. Using a rasp seems like a good idea.

I don't have such glue neeleman, nor a PUR gun, so that's not an option. I do have montagekit, which is very strong. I'm gonna try both montagekit and thinset for a small test and see how both perform.

  Have you considered using Wedi board?

Nigel. I didn't, no. I hadn't considered that, but it seems a bit much work to me to use it. Would require to make a frame for the boards, and the problem of how to fix the frame to the tiles. I'm going for Ytong blocks.

 

[tony_sheehan]

I have to say, judging by your photo, I'd just replace the shower tray....

 

[AlexThePalex]

I have to say, judging by your photo, I'd just replace the shower tray....

Perhaps, but as explained, cost matters. And it's only the plastic profile on the bottom that's broken, the rest is fine.

 

[festooldude]

Why cant you just use limestone bricks and morter? Put them up vertically.. U can even
Use the glue neeleman suggested.

Rick

 

[Rob Z]

Alex,

I can't completely visualize what your plan is, but this is interesting to me because I have been doing bathroom remodels for the past 25+ years.  Are you going to use the new material to fill in under and inside the broken area of  the shower base, and roughly follow the profile of the outside curve of the shower base?  Or, are you going to set the new blocks outside the broken area to conceal the damage, and then cover the blocks with tile?

Either way, I think Nigel's suggestion for Wedi board is a good one. You wouldn't need to make a frame because you can laminate layers of Wedi together with thinset. The thickest Wedi panels I have bought are 50 mm/ 2", so you would only need two or three layers of Wedi to fill the area. (Maybe panels thicker than 50 mm are available in Europe?) The only downside to this is that you would end up with a good-sized piece of Wedi that wouldn't be used. 

Rob

 

[Nigel]

  Have you considered using Wedi board?

Nigel. I didn't, no. I hadn't considered that, but it seems a bit much work to me to use it. Would require to make a frame for the boards, and the problem of how to fix the frame to the tiles. I'm going for Ytong blocks.
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In that case you can cut them with carbide tooth saw[expensive] as you know or an angle grinder [dust!]. Alternatvely do you have plaster blocks there?In France you can get marine grade for showers and they are cheap and you can cut them with a normal saw.They are more usually used for showers than ytong/siporex for some reason.Just a thought but this Ytong/Siporex stuff is not like Thermalite[UK] blocks and a lot harder.I reckon you might struggle to cut it with a normal saw.

Alex,

Either way, I think Nigel's suggestion for Wedi board is a good one. You wouldn't need to make a frame because you can laminate layers of Wedi together with thinset. The thickest Wedi panels I have bought are 50 mm/ 2", so you would only need two or three layers of Wedi to fill the area. (Maybe panels thicker than 50 mm are available in Europe?) The only downside to this is that you would end up with a good-sized piece of Wedi that wouldn't be used. 

Rob

You are quite right Rob and it is the obvious choice as it is made for the job and so easy to use,however it isn't cheap.50 mm is the max I think.As you say you would have some left over.....

 

[AlexThePalex]

Why cant you just use limestone bricks and morter? Put them up vertically.. U can even
Use the glue neeleman suggested.

Rick, is there a benefit of using limestone over ytong? As for the glue, I can't even buy that stuff, I'm a hobbyist and the DIY stores don't carry that, and I'm not gonna invest in a glue gun either for such a small onetime job. The home owner wants it done as cheaply as possible.

This morning I've set up two test pieces, one with thinset and one with montagekit (sorry, don't know the English word for that, it's glue), and see how strong they are when hardened.

 

[AlexThePalex]

I can't completely visualize what your plan is, but this is interesting to me because I have been doing bathroom remodels for the past 25+ years.  Are you going to use the new material to fill in under and inside the broken area of  the shower base, and roughly follow the profile of the outside curve of the shower base?  Or, are you going to set the new blocks outside the broken area to conceal the damage, and then cover the blocks with tile?

Yeah, I could have explained that better. The broken shower base will be trashed and I want to fill the area right under the tub so the tiles will run flush to edge of the tub.

Either way, I think Nigel's suggestion for Wedi board is a good one. You wouldn't need to make a frame because you can laminate layers of Wedi together with thinset.

I didn't know about Wedi board, but when I googled it it looks like those waterproof plaster kind of boards. The videos I saw made it look quite expensive to use, and that's not an option for the H.O. But I'll see in the store what it would cost, doesn't hurt to be informed. If you say you can laminate it with thinset, that could come in handy. 

 

[AlexThePalex]

In that case you can cut them with carbide tooth saw[expensive] as you know or an angle grinder [dust!]. Alternatvely do you have plaster blocks there?In France you can get marine grade for showers and they are cheap and you can cut them with a normal saw.They are more usually used for showers than ytong/siporex for some reason.Just a thought but this Ytong/Siporex stuff is not like Thermalite[UK] blocks and a lot harder.I reckon you might struggle to cut it with a normal saw.

I got me a wood saw for 3 euros, so as you can see, I will spare no expense. [smile] Doesn't matter if it's trashed afterwards. I'll see if I can buy such plaster blocks at the DIY store. How do you glue them?

 

[Rob Z]

Alex, maybe I understand better what your plan is.  If I follow you, you are going to remove that entire piece that serves as an apron, leaving the shower tray/shower base in place.  If so, that really makes me think the Wedi is a great choice.  If you want to tile that vertical part (the apron) that transitions from the tile on the floor to the underside of the shower threshold, then you could cut keystone-shaped pieces of Wedi and stand them in place like a soldier course of brick. Choose  a size of a piece that will closely follow the arc formed by the curb of the shower base.

Wedi is easy to cut (hand saw, jig saw, RotoZip or even a track saw with a cheap or worn  blade).

The 50 mm Wedi here is sold in panels 24" X 8' (although is might be a metric measurement close to 8' ?).  I buy both the 50 mm Wedi and 50 mm KerdiBoard, and the price is extremely reasonable compared to the amount of labor to get to the same results using framing or masonry techniques.

 

[tjbnwi]

I'm with Rob on the product, but I'd use bendy Kerdi in a couple of layers.

http://www.schluterkerdiboard.com

Tom

 

[NL-mikkla]

Interesting, the thing that I fear for is that the tiles do not follow the contour of the tub due to the size.
Meaning the edges of the tiles will stick out or you have to make a weird shaped edge?

Off course when you use something like Mosaic tile sheets it won't be a problem.
But beware when you use bigger tiles like 100mm x 100mm

BTW, I think the Ytong (smallest size available is good enough) is a good choice together with the montagekit.

 

[neeleman]

As Alex mentioned before it has to be done cheap.
Although the first priority should be that it has to be done GOOD, because of the danger of leakage underneath the shower.
You should explain this to your client.

Wedi and Kerdi board don't come cheap and are only sold in shops for companies with a VAT number.
And the quarter round curve is not an easy task for standard Wedi/Kerdi board.
Curved forms can only be made by making grooves in the board (see photo).
Only Wedi has a special Curved Board but they don't come cheap.

Tiling a curved area with large tiles (±100 mm) is another problem.
You have to cut the tiles in smaller pieces and then the sharp sides are exposed even with grout in between.

 

[tjbnwi]

Only Wedi has a special Curved Board but they don't come cheap.

Not true. Schluter has bendy board that is pre-grooved. I've used it more than once.

http://www.schluterkerdiboard.com

It is shown in the link I posted above. As to cost, you have to balance labor and material cost to get true cost.

Tom

 

[Wuffles]

Just a thought but this Ytong/Siporex stuff is not like Thermalite[UK] blocks and a lot harder.I reckon you might struggle to cut it with a normal saw.

Really? I'm not familiar with the brand, but the description sounded like them to me. If so, you might have a problem using a normal saw [embarassed]

I'd still rip out the shower tray and start over. Regardless of the minimal extra cost over your time spent messing about.

Best of luck.

 

[AlexThePalex]

Looked at Wedi board, the brand is not available at my DIY store, but there's something like it, and it is very expensive, considering I need just a tiny bit, but I have to buy a 250 x 60 cm board for 75 euros.

Anyway, I don't see why Ytong blocks wouldn't work, they're used very much over here for bathrooms. Strong, light, cheap and waterproof. Just 4 blocks cost me 8 euro total. I just wanted to know the best way to cut and glue them. Cutting worked out nicely with the cheap wood saw, so that part is covered.

So all I need now is the right glue to glue them to the tiles, which are of course very smooth, so that might be a problem. You can use a special thinset to do tile over tile, so I was hoping I could use that to glue the blocks to the floor tiles. I've set up a test piece with thinset, and one with montagekit, a very strong glue meant for construction purposes. I've had good results with it on laminate which is also pretty smooth, so perhaps it will also work on tiles. It doesn't need to be superstrong, just strong enough that if somebody bumped into it with his or her foot it would not be damaged.

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Off course when you use something like Mosaic tile sheets it won't be a problem.

Yep, that's exactly what I'm going to use, 4x4 cm mosaic tiles. With the small size it's easy to follow the contour.

Although the first priority should be that it has to be done GOOD, because of the danger of leakage underneath the shower.
You should explain this to your client.

That's not going to be a problem. I'll use a good waterproof tile filler, and caulk the sides off with high quality bathroom caulk. By the way, the apron that was in place had no caulking at all, so water could run underneath it. But it's not a big deal because the area under the tub is also tiled.

I'd still rip out the shower tray and start over. Regardless of the minimal extra cost over your time spent messing about.

First I looked to see if it was possible to order a new apron and simply replace it. In that process, I found out what an entire new tub costs and with labour involved that would turn a €100 job into a €350 job. Quite the difference.

People, thanks again for all your input, it's a great help to me.