Is it usually the case that planed wood (from a yard) is typically 5-6mm smaller that the quoted dimensions? (Quoted dimensions being sawn)
And if I buy sawn (like for joists) is it likely to actually be the size it's sold as?
T'other is:
I need to lay some floorboards (normal or engineered) on battens on concrete (wooden floors in some rooms were always in our plans).
Normally I believe you do this onto 2" (50mm) battens - would there be any harm in going thinner, like 25-30mm finished size, as long as I have enough to screw or secret nail the boards to?
Yes. Known as planed all round (PAR). You also hear of "ex such-and-such", where such-and-such is often imperial e.g. "two by four" or whatever.
That is most likely, but you need to check. In these days of "consumer friendly" wood yards and such you may find they're trying not to confuse the less-knowledgeable and ending up confusing everyone.
Someone with practical experience of this will be along in a moment ...
That's normal for PSE (planed square edge) or PAR (planed all round) - both mean the same - and it will be the same for all planed timber (unless you ask for a particular, non-standard planed dimension, and pay extra for it).
If it's sold as "rough sawn" it will be the size - or near enough.
If it's sold as "dimension saw" it will be the exact size as stated (or required).
No problem as long as you use shorter fixings - but if you are secret fixing through the tongues of the boards you may find that your fixings could be too short to get a good grip or be able to be 'skewed' enough to even obtain a grip (not a certainty, but it should be considered when using 'thin' battens).
If the concrete-screed has not yet been laid, why not 'sink' the 2" battens into it during the laying - as per normal practice with such a floor construction?
This is a little more involved than this rather bald statement, but well worth looking up the method and considering it - especially if your floor levels are restricted (as I suspect from your suggestion of using thinner batten).
1) Isolate with a dpm liquid or solid from the concrete (even if a screw is going thru!)
2) provide cross ventilation by gaps in timber skids
3) use only pressure treated skids (roof battens? ) not cut or worked after treatment and if you HAVE to cut
4) Immersion treat 12 hours with an OS solvent fungicide
5) allow a gap all around for expansion
6) if you have UFH make the board as thin as possiible and consider using tiles
7) Use only vac vac treated (Protim etc) floor boards of a timber that is permiable (eg Scots pine) or timber that is naturally durable
Generally concrete and timber are not a good mix but it can be done with care!
Nowadays structural timber is usually sold "regularised and treated". Regularised means it's "hit and miss" planed, the corners radiused, then tested to meet the deflection standard (e.g. c16, c24) for that section. So it will measure slightly under the stated dimension, but conforms to the test requirement of the stated section.
snipped-for-privacy@atics.co.uk coughed up some electrons that declared:
Hi Chris,
I was debating polythene sheet or paint on DPM. Probably use paint-on. I was going to use brass screws or stainless to fix.
Hadn't thought of that. I'd planned to leave a gap at each end (for expansion too), so there's a bit of ventilation up and under the skirting, but this is a good idea too.
Sounds sensible. As the current request from SWMBO is oak floorboards (I agree - nice and hard wearing, yet simple) I wonder if it would make sense to use the same material for the battens? (with extra chemicals)
Just to check - anything against oak here?
The other option was to use engineered, floating on fibre board on top of a plastic DPM (bit like laminate) - but seeing as I may take the floor up a few cm to allow insulation under the bits that are tiled, this seemed a good way to get wooden bits (bedrooms) to the same height and cope with any minor lumpiness in the floor (trim/pack battens if needed).
It helps to talk sensibly with the wood merchant before asking for a discount(!). Also I need a 2 or 3 8x2's upstairs (original are imperial) so I'll measure and see if a standard metric size is equivalent or whether I'll need to ask to have it planed down.
BTW - old floor so battens on top. Have determined I can lose upto 40mm height before bumping head on door frame so can afford to raise the floor a bit to avoid it being cold.
As you haven't said what the 8 x 2s are for, so I will presume that they are for floor joists.
If that is the case, don't worry too much if the metric ones are undersize (and they will be) - simply place the timbers on to of a piece of timber or slate packing (whichever is needed [1]) to bring the tops to the correct level.
BTW, as a general rule, standard metric sizes are always smaller than the old imperial sizes.
[1]
Use timber packing if the joists are resting on a timber wall plate.
Use slate packing (or similar) if the joists are resting on the brickwork.
They're for upstairs, due to a bit of bodgery by the attic-conversion bloke in 1975-ish. 600mm span between two joists where most are 450mm (bouncy floorboards) and a couple in a high load area are 4x2 on top of 4x2. While I have the place stripped, it should fairly easy to slide a couple of extras in. They go onto wooden wall plates, so I'll pack them with timber as you suggest.
If you buy Kiln dried sawn, then it should be pretty close to quoted size. If you buy CLS (aka regularised) then it is a bit undersized (but smoother and more regular).
I would have thought 25-30mm is more "normal" than 2" for this sort of application (unless you have lots of sloping floor to correct!)
Planed (PAR or P4S) has a lovely finished surface and is usually how pine is sold for finish joinery.
Hit and miss is what they do to structural timber - the machine takes off enough material for the timber to fit through the stated dimension (e.g. 47 * 195 mm), but there may be hollows etc, that miss the planer blades.
John Rumm coughed up some electrons that declared:
Thanks John.
OK - I'd just been reading the Black&Decker "Complete Guide to Flooring". It's American, but the techniques look pretty much the same. That was where I got the 2" from.
*cough*
That lumpy kitchen may get the wood treatment. SWMBO is thinking that's a good idea, and I've nothing against it. It would mean that a) I can screw the battens right through into the concrete slab with frame fixings and stop worrying about the condition of the various layers of screed; b) Take my time to laser the battens to get an even floor finish. Depending on the type of DPM, I thought I could screw the battens loosly, and adjust until flat, then squeeze some latex compound under any gaps to bed the battens in.
Pretty much yes, if you bought 2 x 1 PAR (50 x 25) it would actually be nearer 18 x 44. Places like Wickes however now mark PAR timber as actual finished size, so you have to look for 18 x 44.
Erm, ain't that going to be one with the UFH heating pipes on it?
(I think given the choice of whizzing up a few bags of latex, dumping on the floor and dragging level with a plank, or spending hours painstakingly scribing loads of battens to get a level top surface, I might opt for the former!)
SWMBO's involved in the design stage - there may be randomness... I'm also adding randomness depending on what transpires as I try to solve awkward problems - you know...
I'm ambivalent. The floorheater products can operate with wood (the bedrooms get wood eitherway so I did consider this earlier).
I half agree on the latex thing. 2-3 bags on the low half of the room (in front of the fire which is -4 to -12mm in patches) would bring that up to the datum (hall floor). The other half of the room is nominally +4mm to
+6mm with the bay rising to +12mm. It's hard to believe that it used to be a *lot* worse(!).
No - I wasn't planning on scribing the battens. I was considering laying long undersized battens, loosly screwing down, using the screws (and wedges) to pull down until it's straight and aligned with the neighbouring battens, then injecting a bed of super-high quality compound[1] under any gaps to form an in-situ bed.
[1] Topps have a sample "puck" on their counter made from something that seems as hard as iron - must see what it is
I could use thinner battens on the high half of the room and plane down the
2 or 3 that are in the very high area.
I don't know - it's probably a daft idea - I'm just trying some lateral thinking. It would require less compound, it wouldn't require fast working with barrow fulls of latex and I could piddle around more until it's right.
I have to add that when I showed my B&D Flooring book to our 5 year old daughter, she had a totally different opinion to SWMBO.
Daughter says we must have tiles. SWMBO likes wood. And tiles... I think tiles are marginally better in a kitchen but hardwood would be OK - and less dangerous when 3 year old son falls on his head on them, which he will because he's a boy...
Bedrooms definately get wood of some sort. Bathrooms get tiles obviously (but their floors are already torn up to the concrete so I get to do them right from the get-go). Hall and back lobby are still up for decision.
It's a bit like trying to get the UN to agree. Electrics are so much easier - I've done it before, I decide which manufacture gets used, so everyone else just has to pick the look from the catalogue :)
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