I've just taken delivery of a load of 135x19mm T&G oak floor planks for the
two downstairs reception rooms, and whilst I finish some other jobs and wait
for it to acclimatise I'm going through the detailed planning for it's
installation.

It's a Victorian terrace, so the floor downstairs is traditional joists over
a ventilated cavity, and of course all the services (gas, heating, electric)
are routed under the joists. A couple of the joists are knackered -
previous damp problems caused mild rot and a subsequent infestation of
wood-boring weavils - so they will be replaced with new, treated joists, so
I'll need to get most of the existing boards up to carry out that repair.

The people that delivered it expressed surprise that I wasn't going to
install it straight over the old boards, but I really don't want to raise
the existing floor level by another 19mm, and on top of that I'm really
concerned about access to the underfloor should the necessity arise in the
future.

My plan, therefore, has been modified from my original intention of screwing
& plugging the new floor straight onto the joists (this seems like a
ridiculous amount of work and complete overkill) and instead installing a
WBP ply subfloor & secret nailing to that, but creating a couple of
removable sections with the boards secret nailed to the ply, but screwing
and plugging those sections through to the joists instead of fixing them
permanently.

This seems to have a couple of advantages, namely

1) it creates a nice, flat subfloor for easy laying of the new floor;
2) it means that the boards will be somewhat protected from the humidity
variations in the ventilated cavity and hopefully prevent cupping and
warping;
3) the boards aren;t end matched (t&g each end) as I'd expected, so I won't
have to ensure that joins are above the joists.

However, there are a couple of questions about this...

- is 9mm ply thick enough to nail into, and is it enough to provide strength
for any joins that occur between joists (they're 14" centres)
- which ply to use? Champion stock Far Eastern WBP, Shuttering Ply WBP, BBA
Approved Construction Ply WBP, Marine WBP, at widely varying cost
- when secret nailing, is it necessary to pre-drill? I'm concerned about
nails splitting the tongue. Or will a (hired) nailer prevent this?

If 9mm isn't up to it, then I could just about accomodate 12mm, but 18mm
would be way too thick & I'd have to rethink (again).

Oh, whilst I think about it, I'll want a finish to darken the floor. Wax?
Oil? Any suggestions welcomed...


cheers
Richard


--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"Andy Hall" wrote in message
...
On Tue, 22 Jul 2003 14:07:47 +0100, "RichardS" noaccess@invalid
wrote:

snip

Thanks, Andy. Inline comments.....



However, there are a couple of questions about this...

- is 9mm ply thick enough to nail into, and is it enough to provide
strength
for any joins that occur between joists (they're 14" centres)

I think from the strength point of view, 9mm should be OK, but I do
wonder about whether it is going to give adequate holding to the
nails. I have concrete floors and the boarding was fitted onto
18mm pressure treated softwood battens. The boards were then secret
nailed through the tongues into those.



Nails holding is kind of my primary concern. If I can manage to get away
with 12mm instead it may be better.


- which ply to use? Champion stock Far Eastern WBP, Shuttering Ply WBP,
BBA
Approved Construction Ply WBP, Marine WBP, at widely varying cost


- when secret nailing, is it necessary to pre-drill? I'm concerned about
nails splitting the tongue. Or will a (hired) nailer prevent this?

You shouldn't need to as long as you use the correct nailer and nails.


ta, that's reassuring.


If 9mm isn't up to it, then I could just about accomodate 12mm, but 18mm
would be way too thick & I'd have to rethink (again).

I would talk to the supplier - they may have some ideas. Some
movement is important for oak boards anyway to allow for changes in
moisture content. However, you don't want too much......


Can't quite get my head around this.

I'm quite familiar with dimensional change when it comes to moisture change,
and if it were being installed as a floating floor I'd install it as I would
a laminate and leave an expansion gap around the edge.

However, it isn't - each plank will be nailed to the subfloor, which being
ply will be relatively dimensionally stable.

If the floor were to expand then the centre might stay put, and each board
away from the centre would move laterally by a linearly increasing amount.
Therefore the edge boards may move by anything up to 1cm perhaps. This
obviously can't happen without them ripping the nails out.

Am I missing something, or are you saying that the boards just shouldn't be
cramped up too tightly together? The question appeared a week or so ago
about leaving an expansion gap, and I questioned that then, and also when I
asked a related question a long while ago it was suggested thatif anything
the boards might shrink, opening up gaps between them slightly (though being
T&G it won't matter too much).

I certainly need to understand this particular aspect of the board's
behaviour before I install if I am to avoid a costly mistake!


Oh, whilst I think about it, I'll want a finish to darken the floor.
Wax?
Oil? Any suggestions welcomed...


I used an oak oil which is a blend of boiled linseed oil, turpentine
and beeswax. Three coats of that - one each day and wiping off the
last two coats after 30 mins.

For maintenance I use beeswax (just a small amount) with a floor
polisher.

The effect is more or less satin in appearance and a honey colour.
If you send me an email I'll send you some photos to illustrate.


I'll take you up on the offer, thanks. I may be after something a little
darker though - more akin to the colour of church pews (a lot of church
woodwork was made out of oak, wasn't it? it's been a long time...)

One other useful point is that if the boards are random lengths and
widths (and probably shades and knots as well) try to keep them that
way and avoid grouping. One floor that I saw once had all of the
boards with knots down one side and it looked really weird.


Ah, already clocked that one from looking at the pile! Yes, laying the
boards out loose on top before installing seems to be quite a wise move!


.andy

To email, substitute .nospam with .gl


many thanks
Richard

ps. was there much response to the suggestion of a meet in London?


--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

RichardS wrote:
I've just taken delivery of a load of 135x19mm T&G oak floor
planks for the two downstairs reception rooms, and whilst I
finish some other jobs and wait for it to acclimatise I'm
going through the detailed planning for it's installation.

Who supplied it? It may be very dry, in which case you don't need
to let it "acclimatise".

[ ... ]

My plan, therefore, has been modified from my original intention
of screwing & plugging the new floor straight onto the joists
(this seems like a ridiculous amount of work and complete
overkill) and instead installing a WBP ply subfloor & secret
nailing to that, but creating a couple of removable sections
with the boards secret nailed to the ply, but screwing and
plugging those sections through to the joists instead of fixing
them permanently.

I don't like the sound of this *at all*, I'm afraid.


This seems to have a couple of advantages, namely

1) it creates a nice, flat subfloor for easy laying of the new
floor;
2) it means that the boards will be somewhat protected from the
humidity variations in the ventilated cavity and hopefully
prevent cupping and warping;
3) the boards aren;t end matched (t&g each end) as I'd expected,
so I won't have to ensure that joins are above the joists.

However, there are a couple of questions about this...

- is 9mm ply thick enough to nail into, and is it enough to
provide strength for any joins that occur between joists
(they're 14" centres)

14" centres? You will lose minimal material going straight on
to joists. It's only a 12" gap. 9mm ply is *nowhere near*
enough to nail into on its own, you will find lifting problems
& have to re-do.

IIWY I'd lift the old floorboards (may be saleable), fix any
joist/sleeper/dpm/infestation/service problems, and go straight
on the joists. Where you may need access (is the void deep enough
to enter and work?) screw the boards down, removing the under-
tongue of the last.


- when secret nailing, is it necessary to pre-drill? I'm
concerned about nails splitting the tongue.

Depends on the timber and the nail (use square-ended as in
floor brads, not as in wire nails).

If 9mm isn't up to it, then I could just about accomodate 12mm,
but 18mm would be way too thick & I'd have to rethink (again).

I just wouldn't do it. If you really want a vapour barrier,
use pitch paper or even polythene DPM. You might give some
consideration to insulation between the joists, too, such
as jablite.


Oh, whilst I think about it, I'll want a finish to darken the
floor. Wax? Oil? Any suggestions welcomed...

I wouldn't use varnish of any sort, oil first/wax after should
be fine. It will need a polish every litle while, but it's
easier to do this than re-varnish!


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