Wooden Floorboard project

[p1esk]

TA14 said:

Jimmyarm said:

How do floorboards resist woods natural tendency to expand/shrink with temperature and humidity fluctuations ?

Always thought the gaps were there to account for this but every one seems to fill them in =)

In most houses floorboards just shrink. When they are put in they are put in under pressure http://www.tradetoolshop.com/faithfull-flooring-cl... with no gaps but the moisture content in the wood is higher than that of the finished house so they shrink and shrink. People who fill in the gaps with slivers have them become loose because the floorboards shrink more but you don't get buckling due to expansion. One advantage of chipboard flooring I suppose.

If replacing existing t & g floorboards, how important is it that flooring grade chipboard is used? I ask this because I would prefer to use normal 18 mm chipboard with plain edges, rather than 18 mm flooring grade chipboard, which apparently always has t & g edges.

In a previous house I replaced an area of t & g floorboarding with normal chipboard of matching thickness, and it didn't seem to produce any problem, which is why I'd prefer to do that again.

[King Herald]

guindilias said:

When I bought my 1967 built semi 10 years ago, I ripped up the 1970 style carpets and saw that the boards were all chopped when the central heating was bodged in. Decided to bin the boards, and stick in brand new ones, all butted up tight, glued, and then varnished with Diamond coat varnish.
The worst thing I ever did in this house was to not even think about putting in some insulation underneath, and a membrane.
That, and hammering in 700 floor brads by hand. Even my legs hurt after doing that, and I don't hammer with my legs!

You can buy or rent an air-nailer for this sort of job. I have a small 'brad gun' as it is called in This Old House.

Mine cost about 30 notes from Screwfix, but requires a small air compressor as well. Renting would be a better option for anybody laying a whole floor.

I was always under the impression a small expansion gap should be left when laying floorboards, to allow for the seasonal moisture change. I used B&Q cedar floorboards to make a garage door a few years ago, and that would widen/shrink a full half inch through the year. I left no gaps, and it caused havoc with the door fit.

For insulation, I heard you can nail battens halfway down the boards, lay a strip of plywood in there, then lay insulation on that. This is if you have the open soil floor underneath and want to retain air circulation under the house.

[bigdom]

p1esk said:

If replacing existing t & g floorboards, how important is it that flooring grade chipboard is used? I ask this because I would prefer to use normal 18 mm chipboard with plain edges, rather than 18 mm flooring grade chipboard, which apparently always has t & g edges.

In a previous house I replaced an area of t & g floorboarding with normal chipboard of matching thickness, and it didn't seem to produce any problem, which is why I'd prefer to do that again.

Flooring is normally P5 grade (moisture resistant). If you have enough depth 22mm would be beneficial.

https://www.roofingsuperstore.co.uk/product/caberf...

[TA14]

p1esk said:

TA14 said:

Jimmyarm said:

How do floorboards resist woods natural tendency to expand/shrink with temperature and humidity fluctuations ?

Always thought the gaps were there to account for this but every one seems to fill them in =)

In most houses floorboards just shrink. When they are put in they are put in under pressure http://www.tradetoolshop.com/faithfull-flooring-cl... with no gaps but the moisture content in the wood is higher than that of the finished house so they shrink and shrink. People who fill in the gaps with slivers have them become loose because the floorboards shrink more but you don't get buckling due to expansion. One advantage of chipboard flooring I suppose.

If replacing existing t & g floorboards, how important is it that flooring grade chipboard is used? I ask this because I would prefer to use normal 18 mm chipboard with plain edges, rather than 18 mm flooring grade chipboard, which apparently always has t & g edges.

In a previous house I replaced an area of t & g floorboarding with normal chipboard of matching thickness, and it didn't seem to produce any problem, which is why I'd prefer to do that again.

In short you'd probably get away with it.

I don't know much about flooring grade chipboard but at least it's t&g without that you have no load spreading ability especially if a large load (piano/bookcase/aunt agatha in high heels) is placed mid-span. I doubt it would stand up to a structural analysis or pass building regs. Most people only load their floors to less than 1/3 capacity but some have libraries and all sorts of things (rave parties? or whatever they're called these days)

Why would you prefer to use normal chipboard?

[TA14]

King Herald said:

I was always under the impression a small expansion gap should be left when laying floorboards, to allow for the seasonal moisture change. I used B&Q cedar floorboards to make a garage door a few years ago, and that would widen/shrink a full half inch through the year. I left no gaps, and it caused havoc with the door fit.

IIRC moisture content is about 20% in wood outside and 8% in houses (in the seventies so probably 6% now) so using floorboards for an external door was always going to result in expansion> It would have ben best if you could have left the boards outside for a few months (stored properly) and read up on frame construction (introduced circa 16th century?) which was developed for that reason

[King Herald]

TA14 said:

IIRC moisture content is about 20% in wood outside and 8% in houses (in the seventies so probably 6% now) so using floorboards for an external door was always going to result in expansion> It would have ben best if you could have left the boards outside for a few months (stored properly) and read up on frame construction (introduced circa 16th century?) which was developed for that reason

When I screwed them to the door frame I should have left a millimeter slack between each board and the next, the tongue and groove was ideal for it, but I didn't think of it at the time, summertime....so as the two weeks of summer drew to a close my door got tighter and tighter in its frame......

I could have removed them and re-secured them, solved the problem, but I just trimmed the edges.

I don't feel too bad, it was one of the few cock-ups on the whole build, of which everything was done by myself, even the roofing, all but the inspection/signing of the Part P wiring certificates.

[p1esk]

bigdom said:

p1esk said:

If replacing existing t & g floorboards, how important is it that flooring grade chipboard is used? I ask this because I would prefer to use normal 18 mm chipboard with plain edges, rather than 18 mm flooring grade chipboard, which apparently always has t & g edges.

In a previous house I replaced an area of t & g floorboarding with normal chipboard of matching thickness, and it didn't seem to produce any problem, which is why I'd prefer to do that again.

Flooring is normally P5 grade (moisture resistant). If you have enough depth 22mm would be beneficial.

https://www.roofingsuperstore.co.uk/product/caberf...

Oh, I hadn't anticipated 22 mm being suggested, and that would cause a problem in that it wouldn't go under the existing skirting boards. FWIW the existing floorboards are about 20 mm, and I get the impression that in normal circumstances 18 mm chipboard would be used as a replacement.

I also note that whereas we normally seem to think in terms of floor joists being at about 400 mm centres, (the old 16"), ours seem to be more closely spaced from what I've seen so far.

All I'm doing for the time being is temporarily opening up small areas of flooring around room edges, to see how the land lies, so to speak. My master plan for UFH is going to need a bit of thinking about.

[p1esk]

TA14 said:

p1esk said:

TA14 said:

Jimmyarm said:

How do floorboards resist woods natural tendency to expand/shrink with temperature and humidity fluctuations ?

Always thought the gaps were there to account for this but every one seems to fill them in =)

In most houses floorboards just shrink. When they are put in they are put in under pressure http://www.tradetoolshop.com/faithfull-flooring-cl... with no gaps but the moisture content in the wood is higher than that of the finished house so they shrink and shrink. People who fill in the gaps with slivers have them become loose because the floorboards shrink more but you don't get buckling due to expansion. One advantage of chipboard flooring I suppose.

If replacing existing t & g floorboards, how important is it that flooring grade chipboard is used? I ask this because I would prefer to use normal 18 mm chipboard with plain edges, rather than 18 mm flooring grade chipboard, which apparently always has t & g edges.

In a previous house I replaced an area of t & g floorboarding with normal chipboard of matching thickness, and it didn't seem to produce any problem, which is why I'd prefer to do that again.

In short you'd probably get away with it.

I don't know much about flooring grade chipboard but at least it's t&g without that you have no load spreading ability especially if a large load (piano/bookcase/aunt agatha in high heels) is placed mid-span. I doubt it would stand up to a structural analysis or pass building regs. Most people only load their floors to less than 1/3 capacity but some have libraries and all sorts of things (rave parties? or whatever they're called these days)

Why would you prefer to use normal chipboard?

Ah well, this may not stand up to rational analysis, but if you have the t & g system and you ever want to remove a section of flooring (for whatever reason), it's not possible to do it without butching the tongues and grooves, whether it's floorboards or chipboard: that's all I was thinking. That might not really make any sense if the likelihood of wanting to disturb the flooring is very low; which it probably is.

If I were to use plain edged chipboard, I was thinking of leaving a very small gap between the panels and taping over the joints. I realise this doesn't take care of any structural concerns, but that was to avoid getting black stripes eventually appearing on the carpet.

As I say, this may be weird thinking, and I may end up 'doing the right thing' after all.

[TA14]

p1esk said:

All I'm doing for the time being is temporarily opening up small areas of flooring around room edges, to see how the land lies, so to speak. My master plan for UFH is going to need a bit of thinking about.

Well if that's all that your doing just create a series of trap doors:- cut out flush to the joists for the length that you want, screw 3x1 to the sides of the joists and use pine t&g to make the trap door (or flooring grade chipboard if you prefer) and that's it. It won't be as strong as the original but giving the existing boards the full width of the joist to rest on means that it almost is. The trap door boards are a slightly shorter span so should be O

[dojo]

I've just sanded back the boards and half the room (extension - newer) seems to have used treated wood, or at least had it treated, it now has a green tinge to it, I've worked it pretty hard with the sander but it's still there, I applied a bit of danish oil but the green still shows through...
Any suggestions??
Thanks

• edit

I think the green tinge may have been woodworm treatment.
I'm using a medium I oak coloured oil, would a darker oil mask the green better?

Edited by dojo on Sunday 4th January 18:32