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Gapfilling in Floorboards

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Gapfilling in Floorboards

Postby Malc2098 » 24 May 2018, 16:40

SD shares a terraced 3 storey Victorian house.

She's ripped up the carpet in the lounge with the LL's permission and exposed some fairly nice looking possibly original floorboards.

She and the sharers would like to retain the boards, but there are the usual gaps.

What are the preferred methods of gap filling and sealing floorboards to prevent drafts?
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Re: Gapfilling in Floorboards

Postby HappyHacker » 28 May 2018, 18:38

I did some research on this for my daughters floor, I think she is now having carpet. have a look at
https://www.theguardian.com/environment ... 1/dec/16/1

They seem to have listed all the options.
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Re: Gapfilling in Floorboards

Postby Malc2098 » 28 May 2018, 18:56

Thank you.
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Re: Gapfilling in Floorboards

Postby RogerS » 07 Jun 2018, 15:18

Missed this one, Malc.

How about glue and sawdust mix ?
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Re: Gapfilling in Floorboards

Postby Malc2098 » 07 Jun 2018, 18:13

RogerS wrote:Missed this one, Malc.

How about glue and sawdust mix ?


I’ll put that on the list. Thanks.
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Re: Gapfilling in Floorboards

Postby Malc2098 » 07 Jun 2018, 18:14

RogerS wrote:Missed this one, Malc.

How about glue and sawdust mix ?


I’ll put that on the list. Thanks.
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Re: Gapfilling in Floorboards

Postby MartinF » 07 Jun 2018, 18:54

There are several videos on YouTube about using pine slivers

https://www.youtube.com/watch?v=prvQRhagLjI

https://www.youtube.com/watch?v=a_wzMq0iu5M

https://www.youtube.com/watch?v=Xwh0Ro1AaLc

I have been using pine slivers to fill gaps in the floorboards in my daughter’s house in France. The floorboards there are old T&G. This creates two problems. Firstly, you have to cut the tongues to allow the slivers to go in fully. Secondly, over the years, the gaps are full of detritus which needs to be cleaned out as, otherwise, the glue doesn’t adhere. This would also be the case with any method using glue. One thing that I haven’t been able to establish is what happens about expansion and contraction of the boards if the slivers are glued on both sides.

In addition, here’s a video about using glue and wood dust – note the comments underneath about staining the boards afterwards and the durability of this method

https://www.youtube.com/watch?v=PVpDtH8TkTw

HTH.

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Re: Gapfilling in Floorboards

Postby stu » 08 Jun 2018, 06:19

I dont think it would be advisable to use an adhesive in the gaps!

Not done it my self but would advise something flexible, to avoid any issues with movement. See if you can find out what they use on the decks of yachts.

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Re: Gapfilling in Floorboards

Postby Mike G » 08 Jun 2018, 06:34

I used brown Decorators' Mate between my bathroom floorboards, because it is flexible and takes a finish. So far it seems to be working well.
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Re: Gapfilling in Floorboards

Postby RogerS » 08 Jun 2018, 07:07

stu wrote:I dont think it would be advisable to use an adhesive in the gaps!

.....
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Doesn't really matter if the glue loses adherence with the floorboard as the gap will be insignificant in terms of draughts/heat loss.
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Re: Gapfilling in Floorboards

Postby stu » 08 Jun 2018, 07:43

RogerS wrote:
stu wrote:I dont think it would be advisable to use an adhesive in the gaps!

.....
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Doesn't really matter if the glue loses adherence with the floorboard as the gap will be insignificant in terms of draughts/heat loss.


I wasn't really concerned with the loss of adherance/draughts/heat loss, more that it would be creating on solid mass of timber and as soon as it moves there's going to be trouble. If it shrinks you could get cracks/splits in the boards which wouldn't look good or be nice to walk on perhaps causing splinters. Possibly worse would be it expanding you only have to search google for timber floors that have failed to see what I mean!

I like mikes idea of using a caulk, easy to use, not too messy and takes a finish.
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Re: Gapfilling in Floorboards

Postby RogerS » 08 Jun 2018, 08:04

We'll have to agree to disagree, Stu. No chance of splinters...that dust/glue mix is never going to pull bits off the original floorboards to create splinters. As for expansion, not a chance and if it did, it''s not going anywhere. I've done quite a few like this...even in a bathroom..and they're all still fine.
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Re: Gapfilling in Floorboards

Postby Coley » 08 Jun 2018, 10:48

Mike G wrote:I used brown Decorators' Mate between my bathroom floorboards, because it is flexible and takes a finish. So far it seems to be working well.
That sounds like the easiest solution. Even if it wasn't an exact colour match I think it would still look good on every joint.

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Re: Gapfilling in Floorboards

Postby stu » 08 Jun 2018, 16:34

RogerS wrote:We'll have to agree to disagree, Stu. No chance of splinters...that dust/glue mix is never going to pull bits off the original floorboards to create splinters. As for expansion, not a chance and if it did, it''s not going anywhere. I've done quite a few like this...even in a bathroom..and they're all still fine.



Well there's a reason that solid timber floors aren't glued and you have expansion gaps. If it was me I wouldn't do it your way.
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Re: Gapfilling in Floorboards

Postby RogerS » 08 Jun 2018, 17:07

stu wrote:
RogerS wrote:We'll have to agree to disagree, Stu. No chance of splinters...that dust/glue mix is never going to pull bits off the original floorboards to create splinters. As for expansion, not a chance and if it did, it''s not going anywhere. I've done quite a few like this...even in a bathroom..and they're all still fine.



Well there's a reason that solid timber floors aren't glued and you have expansion gaps. If it was me I wouldn't do it your way.


Actually many solid floors are glued down.

You're confusing the performance of the actual floorboards with the gaps that are created either by bad fitting, bows in the floorboards down the length and/or shrinkage across the width of the original floorboards - with the performance of what you put into the gaps to fill them once they are there.

There are various methods of fixing solid timber floors ranging from 'pray and hope' laying them onto an adhesive mat (floating fixing) to screwing them through the tongues using Tongue-tite screws, for example. Tongue-tite screws are as good as glue any day.

As for expansion gaps, I remain to be convinced that they actually work. Take the 'traditional' advice of a 10mm gap around the perimeter. Take a floorboard, say, 200mm wide, and let's say that it expands (quite why it's going to expand if it has been properly seasoned in the room it's going into before laying - no-one has yet to tell me how it's going to happen - most floors that I've laid down contract. Just like the OP who has gaps !! If the boards were going to expand then there would be no gaps !!!

I digress. Our 100mm board...say it expands by 0.1%..that's' 0.1mm. So it's going to press against the adjacent board. But that has also expanded by 0.1mm and so is trying to press against the boards to either side. So take 40 boards in a 4m wide room. That's 4mm being applied somewhere along the line. So are those Tongue-tite screws going to be ripped out to accommodate that 4mm of movement ? I don't think so.

You point to a floor that has buckled and I'll point to a floor with boards that weren't properly seasoned first in the room. If there IS any expansion then 99/100 it will result in cupping of each board. So again, no need for the expansion gap around the perimeter.
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Re: Gapfilling in Floorboards

Postby stu » 08 Jun 2018, 17:57

You make some interesting points Roger. So I've done a little bit of digging and found this article
https://www.popularwoodworking.com/wp-c ... vement.pdf

I found it interesting, I hope that you do too as I think it answers some of your questions. I've always assumed that gaps around a floor would be necessary as it's the advice that is always given by all suppliers of wooden flooring. I guess that it has to be a bit of a catch all due to the variances in the fitting of the floor. I think perhaps, we are both right in our own way.

The article suggests, albeit in America, that "most climate-controlled houses change
3 percent to 4 percent MC during a year". I'm not sure how we would compare in the UK - my gut instinct is that we would have a higher variance in humidity, but I've no basis for this thought!) The co-efficient of movement for redwood is .00101 for quarter sawn and .00229 for flat sawn.

So if we work through your example of 100mm wide boards in a 4m wide room with the formula provided (width of board x realtive change in MC x co-efficient of movement), we get

Redwood

100 x 3 x 0.00101 = 0.3mm per board, or 12mm movement for the room as a best case scenario.

Alternatively,

100 x 4 x 0.00229 = 0.916mm per board, or 36.64mm for the whole room worst case.

White Oak - just for a bit of fun

100 x 3 x 0.00180 = 0.54mm per board, or 21.6mm movement for the room as a best case scenario.

Alternatively -

100 x 4 x 0.00365 = 1.46mm per board, or 58.4mm for the whole room worst case.

Interesting, I think, and you can see where just through seasonal changes you might get up to 36mm/58.4mm (Redwood/Oak) of movement in what's not a massive room. Overall, I think it bears out the advice given that you should have an expansion gap. However, if you have a room with constant climate control and well seasoned boards you should be OK.

Hope you all found this interesting!

Just as a slight aside - I dont spend my time looking up this sort of stuff for fun! I've been wondering for a while how to calculate the gaps for T&G panels in doors for a while (it's what I do!) and now I know some of the answer
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Re: Gapfilling in Floorboards

Postby stu » 08 Jun 2018, 18:02

Here's another link from a UK document that suggests a 4% swing in MC for internal joinery, so the higher end of the US numbers.
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Re: Gapfilling in Floorboards

Postby RogerS » 08 Jun 2018, 18:47

There's no denying those figures but tell me this. 36mm movement for the whole room. But there are screws holding those boards down. Are those screws going to be ripped out? Because to have 36mm of movement according to the calculations means that that board nearest the wall has to move well over an inch ! Which is an impossibility with those screws !

I agree that the maths say it should be so but I would argue that the screws defeat the maths.
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Re: Gapfilling in Floorboards

Postby stu » 08 Jun 2018, 19:40

I guess that to a point you must be correct. However with that must pressure there could/must be a release somewhere. Those screws have a small head to prevent splitting the tongues of the boards, that's a possible weakness in vertical holding power. Perhaps with screw fixing the danger is that all the boards cup a bit and it releases some of the pressure rather than a catastrophic failure where the whole floor buckles or even worse pushes out the bottom of a wall (I've heard anecdotal evidence of this but never seen it)

So, going back to the op, I'd suggest something flexible is definitely the way forward and ideally done at the time of year when we are about half way between the high/ low humidity peaks. Although, if it's a bathroom i would imagine that its probably the most stable room in the house being damp all year round!

Anyway, I'm happy that I've learnt something and now can see the technical theory behind the 'wooden flooring must have a gap round it'. So next time someone asks me at least ill know why!

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