Fitting a new floor

[molehill]

Hi, Refurbishing a timber bungalow - ended up replacing all but the roof, it is out in the sticks so log burner and electricity as the energy sources.
Got to the stage of putting in the floor - onto new joists supported on the original dwarf walls - got 45mm height to play with as already put in pvc doors. Would like to put in some underfloor heating as secondary heat supply. Thought to use Kingspan in between the joists then (1) either marine ply or (not so keen 'cos of stories) green chipboard as an undersurface (2) electric cable or mat heaters (3) tiles or a floating wood floor.

Any suggestions please on - have I got enough height to make this floor sandwich and any ideas on ply v chipboard, cable v mat and lastly tile v wood.

Thanks in anticipation.

 

[Richard C]

If you’ve any intention of tiling do not use chip (crap) board, it’s one of the worst tiling surfaces you could imagine & not suitable; you will also have problems with adhesive on green MR board. I suppose you could use chip if overlaying with carpet, laminate or solid wood but its cheap & nasty stuff & I’d go for T&G timber floorboards. If you definitely plan on tiling, use WBP ply of the appropriate thickness (18-25mm) depending on joist size/pitch/span & depending on area usage/load eg light (bathroom, loo etc) or heavy (kitchen, hall etc). You don’t need expensive marine ply; WBP (external grade) ply is made using similar waterproof adhesive on the veneers.

See this very similar topic;
http://www.diynot.com/forums/viewtopic.php?t=282110&highlight=

Re electric UFH; I’m no expert but a cable system may be better suited as you can tailor the heat output of each room more easily. I would also advise you fit an insulated under board directly under the cable/mat to aid heat reflection & reduce warm up time; be warned, electric UFH ain’t cheap to run! If tiling over, bed the cable/mat in a SLC or, in the event of a problem, you will never get the tiles up without destroying the element. If you intend tiling please read the Tiling Sticky & Forum Archive posts before doing any work or buying materials, it could prevent you making disastrous & potentially expensive mistakes.

 

[molehill]

Thanks for reply. Settled some of my thoughts. can you float a t&g floor over the mat/ cable? Like the idea of t&g.

 

[Richard C]

Whatever system you use I suggest you follow the manufacturer’s instructions/recommendations or you’ll invalidate the warranty.

Here’s just one example;
http://www.theunderfloorheatingstor...4QodvUffVg#/diy-underfloor-heating/4531022574

You will need to allow 150w - 200w per sq/m, per room (200w under tiles only) & as your installing the whole property, you will need at least one or more dedicated circuits which is notifyable electrical work; that's assuming your current consumer unit is suitable! I'm also assuming you’re not a part P spark; you can DIY but it will involve a Building Notice, first fix inspection by LABC & testing/certification by a certified spark (note that you cannot do this after you have installed). It’s a lot more hassle & unless you really know what you’re doing, I would advise you get a certified spark to install the required circuit(s), connect up, test & issue you the necessary certificate.

 

[molehill]

On a computer (much bigger keyboard than a phone). sorry for the tardy reply been laying blocks and trying to grab some ply on Adtrader. Followed the threads you suggested last time and does seem lots of money for total of 9kw heating (approx 60 m2). Martin's Money Tips had a fair discussion about costs - £30 for a heater that you can ditch if it breaks. The project is rebuilding a timber bungalow (only the roof remains the same now-do you need any sticks for kindling). It's out in the sticks so only elec /oil /gas to supply heating to compliment a log burner (ok for weekends but not when you need a quick warm through. Current stage is to fit nsulation - looking a the seconds sites as need 120m2 for floor and ceilings (got walls sorted).

should look nice when its finis - bit like the Rome project.

Thanks again for advice

 

[mointainwalker]

RC

You will need to allow 150w - 200w per sq/m, per room (200w under tiles only

What is special about these outputs ? Why not do a heat-loss calculation to ascertain what is needed.

By the way , have you moved or just decided that Nar-fahk didn't need all the publicity ?

 

[Richard C]

What is special about these outputs ? Why not do a heat-loss calculation to ascertain what is needed.

Generally, UFH mats come in 3 sizes;
100w - for background heat e.g. in a bathroom with a primary heat source (radiator);
150w - generally where UFH will be the primary heat source;
200w - mainly for conservatories with high heat loss or where the thermal efficiency of the room is reckoned to be pretty crap;

These outputs will fit most requirements without the need for heat loss calculations but, as with rad size calculators, nothing stopping you doing the full calcs for confirmation if it makes you happy.

By the way , have you moved or just decided that Nar-fahk didn't need all the publicity ?

Very observant; no I haven’t moved.

 

[mointainwalker]

i'm surprised at those outputs and the comments attached to them, Richard.

In a wet UFH system 100 W/m2 is reckoned to be the maximum that is achievable ( pipes on 100 mm centres ) and that would normally be for full heating.

 

[Richard C]

i'm surprised at those outputs and the comments attached to them, Richard.

In a wet UFH system 100 W/m2 is reckoned to be the maximum that is achievable ( pipes on 100 mm centres ) and that would normally be for full heating.

So your point & additional advice is

 

[mointainwalker]

This is the first time I have ever seen outputs with comments such as "Background heat " attached and also that 150W/m2 is judged on this basis to be necessary for domestic heating whereas the water systems cannot exceed 100 W/m2 and are, I believe, normally installed as primary heating systems.

My reply is simply a comment.