Gap between floorboards up to 2mm

[Tech-Art]

Hi
I'm laying recycled jarrah floorboards and I am finding that the timber is not straight. The size is 82mm x 19mm.
On the same joint the gap varies from 0mm to 2mm. I'm using ratchet straps to tighten so there is a lot of force applied. No matter how much I try the gaps can't be closed just because of the timber geometry.
The main reason I want to close the gaps is because they are a dirt magnet. I remember when I pulled them out the gap was smaller and there was still a lot of dust there.
Question 1: Is there a product such as a glue or finish which will fill the gap and expand/contract with moisture changes. Has anyone used the SikaBond T55 for this purpose?
Question 2: What is the recommended gap based on your experience?

[rwbuild]

A good floor does not have an observable gap. A cork expansion joint should be include every 6.0m
It is possible that the tongue is larger than the groove or groove too shallow
You say that you are reinstalling the floor so did you number the boards consecutively when you pulled them up? If you aren't refitting the boards in the same order then you will have a variation.
Ratchet straps aren't going to give you the same cramping pressure as proper floor cramps do. The straps just keep stretching for that last little bit.
I do assume that you cleaned the grooves and shoulders of the tongues back to bare timber before refitting

[Tech-Art]

"It is possible that the tongue is larger than the groove or groove too shallow" No there is enough space
"did you number the boards consecutively" No I did not
"proper floor cramps" I don't have enough space for a proper floor clamp. My bearers are only 19mm thick (please don's ask why)
"I do assume that you cleaned the grooves and shoulders" Yes I have cleaned them thoroughly

Is there a clamp which suits my situation ... 19mm floorboards on 19mm bearers on concrete ... located in Perth, Australia?
Incidentally how much force is supposed to be applied? I have read that some just used the hidden screws to clamp together. Whereas I am using straps, then using hidden screws (also gluing).

[rwbuild]

Have you sealed the concrete or put plastic down before the battens? If you don't you will get sweating and excessive board movement.
In this situation chisel cramp it ie: using a minimum 25mm chisel with back of chisel against the tongue and drive the chisel into the batten at about 80deg to the batten so the chisel leans away from the board then lever back on the chisel to cramp the board.
You said you are bluing the boards. What type of glue?

[Tech-Art]

Yes, I have sealed the concrete with builder's film.
The glue is Sika T55.
Thx for the chisel idea. I will give this a try.

[gibdog]

We have installed second hand timber floors and found by running the floor board though a saw making the groove bigger the floor came together with ease
you must rip it on the underside of the groove
give it a go
gibdog

[Tech-Art]

@gibdog
I have checked the space between tongue and groove and there is a few "mm" spare.
What do you mean by underside of groove. This is a bit confusing to me.

[david.elliott]

I have a couple of sets of old floor cramps. and you can definitely get enough pressure with those. The chisel did not even come close to working for me...

When last used it was to do a jarrah floor to yellow tongue, so I removed the two pawls that locked onto the joists so they sat flat on the floor and used a piece of timber from the opp wall..and a sacrificial piece into the groove...

Used 6mm trowel and Bostik Ultraset and then a secret nailer AND then I top nailed the whole lot into the joists with 75mm nails..12 kgs of them..


If you'd like to have a go with the cramps just drop me a PM

David

[tonzeyd]

Haven't laid flooring down myself, but have tried using ratchet straps to clamp boards together that i didn't have a large enough clamp for.

I found that yes the the straps can tighten up but most of the force is directed in the wrong direction, ie at an angle upwards and thus doesn't exert as much pressure in the direction that you need it.