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I can't see the point unless the floor is very badly made and likely to shrink or deflect. I've never known tiles to crack in my house (old and poor quality slab) or commercially ( new but high quality slabs) or even over hardboard over floorboards. I have seen a crack elsewhere: parallel to a movement joint, so the slab must have been moving. Would a mat have prevented this? Maybe. Summary: in a newbuild of unknown quality I might use it. Otherwise no.

Thanks @Iceverge! That is perfect and you have listed suitable materials that come in cheaper than my estimators quote too 🙂 If we had a bigger budget then I'd look to improve the U value further, but if I don't keep costs down, we'll have to sell when we have finished the build.

MDF here. It's been fine apart from any edges that have gotten wet. It is just mush really when it comes to taking screws or impact. I don't think it'll last the journey. The dust is horrible when cutting too. I'd much prefer to work with pine. Is there any cement board options? Maybe hardiplank etc? I think you can uPVC too but I've never seen it.

Has anyone got examples of Dot and Dab blowerdoor tests(not gamed!)? Did anyone get below 2ACH ? When it comes to passivhaus airtightness the build types I've seen to have achieved those levels are wet plaster, tapes membranes/boards in timberframe, ICF, SIPS. Two one offs were @Gone Wests Icynene TF and an archive building somewhere in England that used Passive purple paint. I haven't come across any dot and dab getting below 0.6ACH.

It’s likely fine without it however we used it and we only had one relatively small crack in the Cemfloor. Both the tilers that quoted for ours said they’d prefer to use it though were happy to quote without it. One of them said he’d just done his house and used it. There’s very little labour in it so it’s not as if it’s an unnecessary upsell.

I'm going to bounce into this thread rather start afresh, Appreciate I'm taking from the forum and not giving much back, but same situation! Cemfloor, Tiles... matting required or not. Two tilers been round, middle aged gent asks how long screed been down, I says 2 years, has the odd (3) crack coming out of doorways where expansion joints were not inserted, asks my opinion on anti crack matting me says no idea you're the expert!, he says 'good, 2 years, I don't think you need it' Younger chappie comes round at weekend would rather install matting! Now I've no idea what to do, it's budgeted for, but if I can put the £15 m2 (supply + install) cost towards doors or other fittings then I'd rather do so. But, belt and braces and all that, will I regret not doing so?

Soft as pine, less knots? At least that's my initial reaction. Sapele is hard as oak, easy to machine and few knots. Cheaper than Tulipwood. But, BIG BUT, comes from old growth forests in Africa and it's now listed as vulnerable so at the very least need to be careful tracing sustainably managed supply and even then are you contributing to an overall market that is problematic. Edit: open pores though so more work than tulipwood if you want to hide the grain.

Thanks John. My system is a mix of both, so will leave alone for now 🙂

If you have access to the settings, they change how slowly or quickly the heat pump responds to change. Useful for some matching of water volume and/or heating system and rate of change to things like return temperature. So for fan coils you can speed things up and thick screed floors slow the whole response down. It acts like a stiff damper in one direction and weak damper in another.

More costly, but is tulipwood a viable material?

@dpmillerWhat do the PID settings do? I get the overshoot/ start range but haven’t fiddled with PID??

Something as simple as a continuous bead of expanding foam at the foot of the plasterboard, before fitting skirtings, will make a huge difference; this prevents air being sucked in at the bottom of the wall preventing convection airflow / travel around blobs of adhesive when dot and dabbing the boards on. Anything done poorly will always perform poorly, as with everything. Other notorious failures are sealing the slab around rising services such as SVP's when there's a cold ventilated void under block & beam. Heating bills go sky-high when you add all these things together.

OK in theory but this never ever happens on site, which is why the "plasterboard tents" are notoriously freezing.

I've replaced too much of it over the years, and external corners defo don't hold up as well as real timber, where hoovers bump into them etc. I guess it's down to how you look after / treat it, much as with anything. MDF needs to be sealed well at the bottom, and ideally painted at the lower and bit of the rear to prevent any effects from mopping / bathroom water spills etc. Bottom ends of architraves seem particularly susceptible. And yes, pine is a PITA and knotting solution etc is a real PITA. Pine needs a lot of prepwork to get the painted surface looking flawless.

MDF every time, far more stable than natural timber. Once used Pine skirting, never again! Had to nail it every 600 just to keep it on the wall while the adhesive set. Mine has been in years, painted, looks the same as the day i did it

If you are wanting to go high performance, something like Marmox Thermoblocks can be used at the wall/floor level to prevent thermal bridging, much better than aircrete, but for the rest of the construction go with dense blocks, they're robust, don't crack easily, no silly rules for wet plastering, and also keep the temperature balanced out over the year (thermal mass! yes i said it!)

Nothing to do with SAP - its a perfectly acceptable inclusion in the U-value calculation and is covered in the U-value conventions document that supports the Bldg Regs/Appr Docs. Done correctly, to MIs, mass air movement behind the plasterboard will not occur.

Aircrete block will generally give a much better psi-value than a medium or dense block (in the same detail). In a typical ground floor/wall junction expect the psi-value with dense block to be approx 3 times higher than with an aircrete block.

Interesting. Our MDF has stood up pretty well. Eight years so far as a busy holiday let occupied about 200 nights a year. We don't go mad with the floor mopping though, because the floor is bamboo. And in the bathroom, I have replaced one small section of MDF with tile because it was suffering from damp.

Less typing and more tiling I guess then! lol.

Thinks... Or are the tiles on counter-battens and battens so that the vent path is from eaves to top of wall?

These are all going to charge to attend, and as said not many installers will want to be left holding someone else's baby.

But the dwg shows a ventilated void. One assumes that is to keep the timber frame 'happy'. You have not got that, it would appear, and the architect, not having seen the builder achieve what the dwg says they should achieve (a ventilated void), as far as I can see, is of the view that it's to a 'satisfactory standard'. I can accept that a cut-in flashing can be OK (though see my earlier comment re render-board and the likely depth of the 'chase') but it neither satisfies you aesthetically nor provides the ventilated void (AFAICS) which the architect specified. The 'finish' may be to a satisfactory standard (to the architect, but not to you, the client) but the 'middle' -the provision of a ventilated void - isn't there, as far as I can see from a none-too-close-up pic. Please correct me if there is some other sort of vent provision in what has been provided. Oh, and almost as an aside, out of interest, what happens at the other end(s) of the 'continuous vent' marked on the detail? To explain, while it appears that you may not have the 'in', do you have the 'out' at the top? The pic does not go high enough for us to see.

Also, depending on tiles used the top cut edge might not look great. Looks good if done well though.

interesting, I’ve seen this on my holidays in the apartments. how have you interfaced with door architraves? We’ve having a modular rustic tile fitted on the floor, I’ll check the catalogue and see what options they have listed to see if it could pass muster!