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ProDave

Laying engineered structural floor on joists

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Engineered structural floor, 190mm wide planks with an Oak finish.  Laid on joists at 400mm centres as a structural floor.

 

Is it best just to secret nail the tongues?  Glue the planks to the top of the joists?  Glue the tongue and groove between adjacent boards?  Or a combination of those?

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The stuff upstairs here is secret nailed. Hasn't moved in 8 years. 

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I ask because it must not creak. Let me spell that out MUST NOT CREAK. So thinking it needs glue as well so nothing can move in relation to anything else.

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Never noticed mine creaking TBH. How thick are the boards? Mine are 22mm and don't seem to move or creak at all. 

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41 minutes ago, ProDave said:

I ask because it must not creak. Let me spell that out MUST NOT CREAK. 

 

I'm completely with you on this goal. Our nailed-chipboard-on-easi-joist-floors creak in our bedroom. We used extra screws in the other rooms, and they mostly don't squeak, but somehow our room was overlooked when we suddenly had to get carpet down at short notice ("In by Christmas!")

 

It. Drives. Me. NUTS! Most nights as I creak my way across the floor on the way to bed I idly wonder how much effort it would be to roll back all the carpet and add some screws. 

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I'm incredibly glad that I opted to bond down our T&G bamboo flooring with Sikabond, to the concrete ground floor and to the T&G OSB first floor.  Best decision I made, I think, as it made the floor really solid, plus the slightly rubbery nature of Sikabond 95 seems to add to the acoustic damping, so the result is a much quieter floor to walk on.  One other thing I did to the first floor OSB was go around and liberally apply PVA glue to every joint in the OSB, then gave it a coat of diluted PVA, worked well in with a soft broom, to not only seal the floor but also try to help get glue down into the OSB T&G joints.

 

I detest creaking floors and staircases, and I spent ages adding additional glued on blocks under our stairs to stiffen them up and reduce the slight noise they made.  I was lucky, in that the stairs were supplied with a box of extra triangular blocks, and I didn't box in under the stairs for a few months.  Although the stairs were creak-free when installed, after a few months one or two treads started to creak, but gluing and screwing extra blocks on every tread fixed it.

 

 

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We used Rewmar MS Polymer adhesive to bond it to the screed on the ground floor and it's completely silent. Next door's isn't laid like that clearly and is horribly creaky and noisy when it's walked on. No idea how that was laid as the builder of their house did it. 

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31 minutes ago, Dudda said:

Glue and screw something like these screws. You shouldn't need to pilot drill the boards if they're engineered. You do with some solid floors like oak which might split.

https://www.ie.screwfix.com/tongue-tite-screws-3-5-x-45mm-pack-of-200.html

 

I stay away from nails where possible.

Hadn't seen those before. I thought screws would be too big hence secret nailing, and glueing as nailing is never perfect.

 

So is the consensus to glue the boards to the joists, or glue tongues and grooves together, or both?

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I too HATE creaky floors, our first floor was bonded with D4 glue ONLY, it has never squeeked once and I am very pleased with it. 

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TBH, I very much doubt that screws do anything much to help once the adhesive has cured, so if you can pull the boards tight without screw and just use a good adhesive I would have though that would be fine.  My experience with using Sikabond 95 (which is just a sticky and thick moisture-curing modified silicone polymer adhesive, like CT1, but developed especially for bonding flooring) was that the stuff worked a bit like a grab adhesive, but allowed some lateral movement when tapping the boards together tightly.  The "suction" of the adhesive was enough to hold them down flat, I found.  The technique was to lay two or three boards at a time, tapping them together tightly, then (making sure there;s no adhesive on you feet) walk over the newly laid boards to make sure they are laid down tight.  I found that the boards didn't tend to move laterally when doing this, but they did settle down tight to the floor.

 

 

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9 minutes ago, JSHarris said:

so if you can pull the boards tight without screw and just use a good adhesive I would have though that would be fine. 

 

No idea if this is the right method as the hubby laid the floor with no previous experience but he used these straps to pull the boards tight whilst the adhesive was curing. Seemed to work ok anyway given it is still stuck down fast. 

 

Oh and if there is any trace of glue on any of the top surface remove it immediately. There were some bits the hubby didn’t notice (I did as soon as I was back from work ;)) and they were a b1tch to remove once dry! 

 

 

 

6FC4DCBB-2A26-4AFA-9048-1F3EA19F7DCC.jpeg

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The reason I suggested the screws is because they pull the boards tight together and holds them as the glue dries. After squeeky boards my next big hate is gaps or poorly fitted floorboards. It allows you to progress much faster. You only need to screw every third joist or second on shorter boards. 

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Next bit of advice needed.  Expansion gaps.

 

So far I have floored the big room

 

oak_floor_2.thumb.jpg.3851b4c8e14d58e8a26b0333bf740366.jpg

 

This room is about 7 metres by 5 metres and the boards run front to back, i.e the 7M dimension.

 

I want to continue this same floor throughout most of the ground floor, i.e continue out of the door opening (just visible on the right of the picture above, a double door opening) across the hall, and into and through the snug lounge.  The look we want is once continuous floor with no gaps or visible joints.

 

BUT if I do that, the total width covered by the floor will be 11 metres.  I am sure I have read you should not exceed 10 metres without an expansion gap

 

So do I need an expansion gap?

 

If so how to make a level unobtrusive expansion gap?  If I do so I will put the gap in one of the doorways so it is covered when the doors are shut.

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