# Forum Home Renovation Flooring  Old timber floors with large gaps

## megworm

Hi All, 
We have purchased an 80 yo Queenslander about 4 months ago. We got it cheap because it was full of termites but its on an awesome block with great potential in the future.  
So we have re-stumped it and fixed all the termite damage and killed the little blighters off (for now!) 
I have pulled up the old Lino and found beautiful old floorboards underneath. There are tongue and groove hoop pine floor boards and some iron bark and various other timbers in each room. The main problem is that a lot of the house used to be deck so the flooring is not tongue and groove and some of the gaps are big. The largest would be around 8mm. A builder has just had a look at it and recommended that we put new flooring over the top of the old flooring, at least in a couple of rooms. We are quite disappointed by this idea.  
With the number of creepy crawlies up here I'm not that keen on leaving them unfilled, but I am aware that filling these gaps would be difficult from reading earlier posts.  
Has anyone got any thoughts on what to do?

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## shauck

Your builder is pretty much suggesting what most would, to achieve a generally acceptable result. If you really want to keep the boards showing, maybe get underneath and use some product to block between the joists, stopping the gaps that way?? Unconventional.

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## WACanetoad

I have come across this problem a couple of times if you use black sikaflex that is used for caulking boat decks and then sanding it achieves quite an effective look. Did it with a crows ash built in verandah and it looked great. Can't remember what the timber was the other times
ben

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## peersy

I would certainly look at two things: 
- sealing from above
- insulating with aluminium concertina foil batts from below (if you can access under the house) 
Concertina foil batts are great for thermal properties, as they perform as good as a 2.0R glass/wool batt. 
Second thing about these gems are they are dead easy to install as they can fit pretty much any joist spacing up to 600mm, they pull out like a fan and staple to the timber joists. They are pretty cheap and one pack will generally do one room. 
Third bonus of the concertina foil batts is they don't provide a nice environment for rodents like conventional fibre batts as the surface is difficult for them to live in. 
You will find if you install the foil batts first, your air drafts won't exist and it might be all the difference you need to be comfortable. If you want piece of mind, glue some thin strips of anything under the bigger gaps and fill them in with timber filler matched to your timber colour if required later on... 
Just a thought! www.concertinafoilbatts.com 
I'm installing under my house now   
Research well and Goodluck!

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## rhancock

Having listened to some of the reports of the deaths while installing metallic insulation recently, please turn off the power before installing foil batts.

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## phild01

> Having listened to some of the reports of the deaths while installing metallic insulation recently, please turn off the power before installing foil batts.

  I would expect the danger more present with ceiling installs than underfloor.  The again I recall reading about one house having exposed live wiring with no insulation at all underhouse, bare runs of wire!

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## rhancock

Not so, most of our wiring is under floor, not in the ceiling.

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## phild01

> Not so, most of our wiring is under floor, not in the ceiling.

  
Not what I meant.  Lights and terminations tend to be more exposed in the ceiling.  Underhouse wiring tends to be terminated inwall and generally the chance of exposed terminations are rare.

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## rhancock

The risk isn't exposed terminations.  The deaths were caused by shooting metal staples into live wires.  The same risk exists for nails and screws.  Turning off the power when working around any electrical cables removes any risk of electrocution.

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## peersy

Exactly, the blame shouldn't be on the foil insulation industry during the HIP. 
More so to the poor governance of quality electrical wiring in QLD and awareness of fixing anything near wiring.

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## phild01

> The risk isn't exposed terminations.  The deaths were caused by shooting metal staples into live wires.  The same risk exists for nails and screws.  Turning off the power when working around any electrical cables removes any risk of electrocution.

  Gotcha, now aware :2thumbsup: .

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## kayzersoze

I have a similar problem to the OP and I was thinking of another possible solution, inspired by the way we did the flooring in the extension of our house. We always intended to leave the existing Baltic pine flooring in place and get it sanded and polished. We didn't mind the gaps - they add a bit of rustic authenticity to the place. When it came time to extend, our builder had already decided we was going to put yellow tongue particleboard flooring directly onto the joists (which he set 20mm lower than existing floor) as he prefers to be able to easily walk around while framing up. We carpeted directly onto this in bedrooms, cement-sheet & tiled over it in the ensuite, and then glued & nailed new kiln-dried Baltic pine boards directly to the YT flooring. Effectively we have a 38mm thick wooden floor. 
So my idea was, particularly in parts of the old house with both gaps and annoying squeaks that wake up our baby as we're trying to tiptoe out of her room, I could buy some more particleboard flooring, cut it to size, lather it with that Liquid Nail Direct Stick glue in a sausage we used for the extenstion (easily the stickiest, most stubborn and hard to remove glue I've ever used), hold it up against the floor between the joists from under the house, and screw it in place. Gaps: gone. Squeaks: hopefully gone. R-value: slightly increased. Cost: minimal. 
Once I'm done I'll go through the subfloor and try out those concertina foil batts in all areas (newly glued particleboard areas, older still gappy areas, extension area, carpeted areas).  
Can anyone think of why screwing & glueing particleboard flooring under old baltic boards is a bad idea?

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## David.Elliott

Sounds reasonable enough, although I'd be tempted to look into battens underneath the particleboard, running along each joist, jacked up until the PB and glue is in good contact with the existing floor and then nail/screw off to the joist. Cannot explain why, but screwing off to the existing floor sounds like not such a good idea...

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## kayzersoze

> Cannot explain why, but screwing off to the existing floor sounds like not such a good idea...

  Yeah I have since thought of a few risks/problems: I think the old boards, now sanded twice, are probably only around 18mm thick. So realistically, I only have about 11mm of purchase for a screw. No idea whether the timber, now very old and in some places evidence of critters, might push upward where a screw is underneath. 
So your idea of battens is a good one.

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## kayzersoze

As for insulation to take care of the areas I won't go to the trouble of gluing particleboard under, I'm dubious of the ability of the concertina foil sheets to seal off wind. We only have baseboards covering our subfloor - on windy days the draft coming up through gaps is significant. I imagine I'd have to tape the overlapped ends of the foil sheets together. Which could be difficult with the whole zig-zag thing. 
Even though subfloor-specific glasswool or polyester batts are pretty dense, I imagine strong enough winds will still seep air in through the cracks, yeah? The installation instructions for the Autex GreenStuf seems to indicate the subfloor needing to be sealed off from high wind for it to work properly. 
So I was wondering about those rolls of aircell foil (essentially bubble-wrap with foil on both sides and tiny holes for the required amount of breathability). My house has 6 bearers total, so 5 gaps between. I could roll out this foil along the length of the house and staple 30-40mm of it to the bearer along a length, then staple it to all the joists along this length. Do it on each side with 100mm overlap in the middle, and tape along the length of this overlap. Essentially I could seal off all the floorboards from the outside world, and have a 90mm pocket of air between foil and boards:  
Obviously the downsides are:
 - difficulty for a sparky if they ever need to find where a power cable enters a wall - but we've been re-wired, and don't need any powerpoint installations for the forseeable future. Plus they can just cut away the foil and we re-tape it.
 - risky if a staple goes through a power cable - but I'd turn the power off and how hard can it be to see whether you're about to staple through a power cord on a bearer or underside of joist?
 - risky if some kind of wear occurs on insulation of power cable and whole subfloor foil becomes live (Don't know the chances of this). 
Plus side: Warm, draft-free house.

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## OBBob

> 1 - risky if a staple goes through a power cable - but I'd turn the power off and how hard can it be to see whether you're about to staple through a power cord on a bearer or underside of joist?
> 2 - risky if some kind of wear occurs on insulation of power cable and whole subfloor foil becomes live (Don't know the chances of this).

  1 - I've always wondered what happens in this situation when you turn the power back on? The RCD trips  (would it?) and you spend an eternity searching for the staple?  
2 - That seems fairly unlikely. I guess in that scenario you'd also potentially have wear between the active and neutral, which also would not be desirable.   
My last place had gaps and the wind issue ... I know if you're going to do it you might as well do it properly but I also think any of the solutions will be a considerable difference (even if a little air still leaks).

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## phild01

If you really want to keep the boards 'as is' and then seal under, you will have a problem with dirt and grit accumulating between the boards or on whatever is placed under them.  Could the boards be lifted and relaid on top of particle board flooring?

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## OBBob

> ... dirt and grit accumulating between the boards ...

  Isn't that called 'character'?  :Biggrin:

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## kayzersoze

> If you really want to keep the boards 'as is' and then seal under, you will have a problem with dirt and grit accumulating between the boards or on whatever is placed under them.  Could the boards be lifted and relaid on top of particle board flooring?

  No to re-flooring like that because I'd then be 18mm higher than extension flooring, but mostly because I could never be arsed to do such a thing in my spare time now the house is mostly complete. If I was starting over though .... different story. 
I'm OK with the dirt and grit. Its what expensive vacuum cleaner obsessions are for. My Nilfisk is so strong it will suck your will to live. It bothers my wife a little though - the 'stuff in the gaps',  and when the little one starts crawling we're worried she might catch a splinter. My solution there is to fence off the smooth, gapless extension floor and let her crawl there to her hearts content till she can walk. Slight overkill since I love a good sock slide and haven't splintered in 5 years on the old stuff. But I'd rather be safe. 
I've emailed Autex about their poly wool batts and my draughty subfloor. Will post their response and any work I end up doing.

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## OBBob

I think Phil meant to remove and replace the floor, not go over the top. But I can see why you wouldn't want to do that. Unfortunately the little one is likely to find a way to splinter herself no matter what you do ... maybe baby knee-pads?  :Smilie:

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## David.Elliott

My last place had gaps and the wind issue ... I[/QUOTE] 
So did mine, and then I realised so did the new place. The only constant therefore was me. That narrowed it down somewhat!
Changed my diet, sorted!

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## OBBob

> So did mine, and then I realised so did the new place. The only constant therefore was me. That narrowed it down somewhat!
> Changed my diet, sorted!

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## energyexpert

I would think that sealing up the air gaps should be the priority. Until that is done air exchange with the underfloor area is going to bring your house and the underfloor to the same temperature. Bulk insulation pressed up against the bottom of the floor boards might do it but may also be visible from above if the gaps are too large. Perhaps the largest gaps could have a board placed underneath them?
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Just Rite Pty Ltd Home Insulation Batts 
181 Gladstone St.
Fyshwick, 2608
Canberra, ACT

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## kayzersoze

> I would think that sealing up the air gaps should be the priority. Until that is done air exchange with the underfloor area is going to bring your house and the underfloor to the same temperature. Bulk insulation pressed up against the bottom of the floor boards might do it but may also be visible from above if the gaps are too large. Perhaps the largest gaps could have a board placed underneath them?

  There are few (if any) gaps big enough for light to get through. Early on I sealed the huge ones up with silicone & packers on the underside, and black silicone on the topside (i.e. inside). Plus we don't have the brightest lights throughout the house anyway. So I'd be surprised if we could see any glass/poly wool batt from inside the house. 
But I agree that sealing up gaps is a priority. I guess I wanted to know if my idea of fixing air-cell (foil covered bubble-wrap) insulation along the bottom of all my joists - done properly - would effectively seal up the gaps anyway? That is, seal the gaps up from the outside world (instead it would just be a gap to a cavity of air between two joists). It would be easier than trying to find & seal up all the individual gaps (which would require moving furniture, and burning a crap load of stinky incense).

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## energyexpert

> There are few (if any) gaps big enough for light to get through. Early on I sealed the huge ones up with silicone & packers on the underside, and black silicone on the topside (i.e. inside). Plus we don't have the brightest lights throughout the house anyway. So I'd be surprised if we could see any glass/poly wool batt from inside the house.  But I agree that sealing up gaps is a priority. I guess I wanted to know if my idea of fixing air-cell (foil covered bubble-wrap) insulation along the bottom of all my joists - done properly - would effectively seal up the gaps anyway? That is, seal the gaps up from the outside world (instead it would just be a gap to a cavity of air between two joists). It would be easier than trying to find & seal up all the individual gaps (which would require moving furniture, and burning a crap load of stinky incense).

   
The product you are referring to is Kingspan's Air-Cell Permifloor. It can provide two in one insulation and moisture management systems and if done properly you will seal up all gaps. Having said that, it's an expensive product. You will be looking at somewhere around $200-220 for a roll that covers 30m2.   ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Just Rite Pty Ltd. Kingspan Air-Cell Permifloor, lowest prices guaranteed!
181 Gladstone St. 
Fyshwick, Canberra 2608

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