I had a bulge in an upstairs floor and have removed some chipboard floor
panels to rectify.

The joists below are split into two parallel sections. The divide being
over a concrete lintel, about 30cm wide. The joist faces touch each
other and have a 10cm overlap, but don't appear to be attached by nails,
bots or screws. One joist span is 3m the other 1m. At this point the
joists were separated by lightweight concrete wall blocks, cemented in.
As the blocks were taller than the joists they caused the bulge in the
floor. I presume their purpose was to hold the joists in place and
prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to
attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I also thought I might buy a mitre saw to get the correct angles on the
struts. For a custom angle these all seem to be electric. Is this an ok
choice

https://www.screwfix.com/p/evolution-r210cms-210mm-electric-single-bevel-compound-mitre-saw-240v/7277p

On 09/07/2020 12:28, Pancho wrote:
perhaps it would be better to use herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to
attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

Herring bone always a good plan and will reduce flexure as well. No need
to be anal about the struts any old angle more or less right will do,
even more so if you use a gap filling glue as well as... you can drive
a nail or indeed a long screw through the joists at an angle to pick up
up on the lower ends.

As I get older I prefer to wast money on screws as its less hassle than
driving nails and does less damage and with a cordless driver, its
relative **** to get them in.


--
Any fool can believe in principles - and most of them do!

On 09/07/2020 12:28:20, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard floor
panels to rectify.

The joists below are split into two parallel sections. The divide being
over a concrete lintel, about 30cm wide. The joist faces touch each
other and have a 10cm overlap, but don't appear to be attached by nails,
bots or screws. One joist span is 3m the other 1m. At this point the
joists were separated by lightweight concrete wall blocks, cemented in.
As the blocks were taller than the joists they caused the bulge in the
floor. I presume their purpose was to hold the joists in place and
prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to
attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I also thought I might buy a mitre saw to get the correct angles on the
struts. For a custom angle these all seem to be electric. Is this an ok
choice

https://www.screwfix.com/p/evolution-r210cms-210mm-electric-single-bevel-compound-mitre-saw-240v/7277p

That is a very small saw.

I've tended to use 'solid' noggins rather than struts. Much stronger.

On 09/07/2020 12:28, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard floor
panels to rectify.

The joists below are split into two parallel sections. The divide being
over a concrete lintel, about 30cm wide. The joist faces touch each
other and have a 10cm overlap, but don't appear to be attached by nails,
bots or screws. One joist span is 3m the other 1m. At this point the
joists were separated by lightweight concrete wall blocks, cemented in.
As the blocks were taller than the joists they caused the bulge in the
floor. I presume their purpose was to hold the joists in place and
prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to
attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I think I would get a nx2 joist (where n matches the depth of your
current joists), and chop noggings off that. Make em a snug fit and
hammer them into place between the joists, then either skew screw them
to the sides of the existing joists, or stagger them, and screw through
the side of the joists into the ends of the noggings.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 09/07/2020 13:18, John Rumm wrote:
On 09/07/2020 12:28, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard
floor panels to rectify.

The joists below are split into two parallel sections. The divide
being over a concrete lintel, about 30cm wide. The joist faces touch
each other and have a 10cm overlap, but don't appear to be attached by
nails, bots or screws. One joist span is 3m the other 1m. At this
point the joists were separated by lightweight concrete wall blocks,
cemented in. As the blocks were taller than the joists they caused the
bulge in the floor. I presume their purpose was to hold the joists in
place and prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard
metal strut from the bottom face of one joist to the top of the next.
So I figure I'll cut wooden ones. This will still be a little tricky
to attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I think I would get a nx2 joist (where n matches the depth of your
current joists), and chop noggings off that. Make em a snug fit and
hammer them into place between the joists, then either skew screw them
to the sides of the existing joists, or stagger them, and screw through
the side of the joists into the ends of the noggings.




I suspect the bulge in the floor was caused by the existing poorly
restrained joists drying out and twisting, pushing up the floor.
I had the same problem but ended up with a crease in the ceiling
below. The builders had used a pair or 9 by 2.5 joists sitting
side by side and fixed together with three 3 inch round nails !.
At one end they were built into the party wall and the other
ends were floating free on top of the false chimney that hid the
baxi back boiler.

I tried using a car scissor jack to push them back together but the
gap at the top of the pair was about 1.5 inches when the bottom was
in contact with its pair. I could slide the whole joist from side to
side, so it wasn't even attached to the chipboard flooring and
obviously carried no weight.

Once they have dried out you cannot remove the distortion without
damaging the floor or ceiling below. Flattening a bulging floor
is just a case of using a power plane to carefully reduce the
part of the twisted joist where the bulge is.

On 09/07/2020 12:36, The Natural Philosopher wrote:
On 09/07/2020 12:28, Pancho wrote:
perhaps it would be better to use herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard
metal strut from the bottom face of one joist to the top of the next.
So I figure I'll cut wooden ones. This will still be a little tricky
to attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

Herring bone always a good plan and will reduce flexure as well. No need
to be anal about the struts any old angle more or less right will do,
even more so if you use a gap filling glue as well as...Â* you can drive
a nail or indeed a long screw through the joists at an angle to pick up
up on the lower ends.

As I get older I prefer to wast money on screws as its less hassle than
driving nails and does less damage and with a cordless driver, its
relative **** to get them in.


+ 1 on both

(also screws are easy to remove even long after).

On 09/07/2020 13:44, Andrew wrote:
On 09/07/2020 13:18, John Rumm wrote:
On 09/07/2020 12:28, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard
floor panels to rectify.

The joists below are split into two parallel sections. The divide
being over a concrete lintel, about 30cm wide. The joist faces touch
each other and have a 10cm overlap, but don't appear to be attached
by nails, bots or screws. One joist span is 3m the other 1m. At this
point the joists were separated by lightweight concrete wall blocks,
cemented in. As the blocks were taller than the joists they caused
the bulge in the floor. I presume their purpose was to hold the
joists in place and prevent twisting.

These blocks appear pretty useless, the cement around the has
crumbled and so they don't seem to serve any purpose, apart from
preventing a catastrophic twist. I could just shave the top off the
blocks and put the floor back down, but thought perhaps it would be
better to use herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard
metal strut from the bottom face of one joist to the top of the next.
So I figure I'll cut wooden ones. This will still be a little tricky
to attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I think I would get a nx2 joist (where n matches the depth of your
current joists), and chop noggings off that. Make em a snug fit and
hammer them into place between the joists, then either skew screw them
to the sides of the existing joists, or stagger them, and screw
through the side of the joists into the ends of the noggings.




I suspect the bulge in the floor was caused by the existing poorly
restrained joists drying out and twisting, pushing up the floor.

That would be a possibility, bu the OP did not mention his joists
actually being twisted, only that the blocks currently fitted would not
work to prevent it if they did. Also if they are taller than the joists,
they will result in a lift in the floor.

I had the same problem but ended up with a crease in the ceiling
below. The builders had usedÂ* a pair orÂ* 9 by 2.5 joists sitting
side by side and fixed together with three 3 inch round nails !.
At one end they were built into the party wall and the other
ends were floating free on top of the false chimney that hid the
baxi back boiler.

I tried using a car scissor jack to push them back together but the
gap at the top of the pair was about 1.5 inches when the bottom was
in contact with its pair. I could slide the whole joist from side to
side, so it wasn't even attached to the chipboard flooring and
obviously carried no weight.

Once they have dried out you cannot remove the distortion without
damaging the floor or ceiling below. Flattening a bulging floor
is just a case of using a power plane to carefully reduce the
part of the twisted joist where the bulge is.

Yup once that far gone, there is no going back to straight. As you say,
planing the top will fix it. Possibly still worth adding some (cut to
shape) noggings to stop any further twist or movement.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Pancho wrote :
These blocks appear pretty useless, the cement around the has crumbled and so
they don't seem to serve any purpose, apart from preventing a catastrophic
twist. I could just shave the top off the blocks and put the floor back down,
but thought perhaps it would be better to use herring bone struts or noggins.

I suspect full height noggins would be easier to fit and secure,
something like 30 to 40mm thick by what ever size would fit in the
height available. Drill some large holes through the middle to allow
some air flow. You can then either add long screws either through the
joist, into the noggin, or from the noggin, at an angle down into the
joist.

Pancho wrote :
These blocks appear pretty useless, the cement around the has crumbled and so
they don't seem to serve any purpose, apart from preventing a catastrophic
twist. I could just shave the top off the blocks and put the floor back down,
but thought perhaps it would be better to use herring bone struts or noggins.

I suspect full height noggins would be easier to fit and secure,
something like 30 to 40mm thick by what ever size would fit in the
height available. Drill some large holes through the middle to allow
some air flow. You can then either add long screws either through the
joist, into the noggin, or from the noggin, at an angle down into the
joist.

Pancho wrote :
These blocks appear pretty useless, the cement around the has crumbled and so
they don't seem to serve any purpose, apart from preventing a catastrophic
twist. I could just shave the top off the blocks and put the floor back down,
but thought perhaps it would be better to use herring bone struts or noggins.

I suspect full height noggins would be easier to fit and secure,
something like 30 to 40mm thick by what ever size would fit in the
height available. Drill some large holes through the middle to allow
some air flow. You can then either add long screws either through the
joist, into the noggin, or from the noggin, at an angle down into the
joist.

Pancho wrote :
These blocks appear pretty useless, the cement around the has crumbled and so
they don't seem to serve any purpose, apart from preventing a catastrophic
twist. I could just shave the top off the blocks and put the floor back down,
but thought perhaps it would be better to use herring bone struts or noggins.

I suspect full height noggins would be easier to fit and secure,
something like 30 to 40mm thick by what ever size would fit in the
height available. Drill some large holes through the middle to allow
some air flow. You can then either add long screws either through the
joist, into the noggin, or from the noggin, at an angle down into the
joist.

a dwang in the near of Scotland...just translating.....


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a dwang in the near of Scotland...just translating.....


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a dwang in the near of Scotland...just translating.....


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a dwang in the near of Scotland...just translating.....


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Kind of begs the question, why was it done that way? M;aye there is more to
the flooring than is obvious. Has the building been modified in some way,
or damaged by fire in the past?
Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Pancho" wrote in message
...
I had a bulge in an upstairs floor and have removed some chipboard floor
panels to rectify.

The joists below are split into two parallel sections. The divide being
over a concrete lintel, about 30cm wide. The joist faces touch each other
and have a 10cm overlap, but don't appear to be attached by nails, bots or
screws. One joist span is 3m the other 1m. At this point the joists were
separated by lightweight concrete wall blocks, cemented in. As the blocks
were taller than the joists they caused the bulge in the floor. I presume
their purpose was to hold the joists in place and prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled and
so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put the
floor back down, but thought perhaps it would be better to use herring
bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to attach
the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I also thought I might buy a mitre saw to get the correct angles on the
struts. For a custom angle these all seem to be electric. Is this an ok
choice

https://www.screwfix.com/p/evolution-r210cms-210mm-electric-single-bevel-compound-mitre-saw-240v/7277p

On Thursday, 9 July 2020 12:29:11 UTC+1, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard floor
panels to rectify.

The joists below are split into two parallel sections. The divide being
over a concrete lintel, about 30cm wide. The joist faces touch each
other and have a 10cm overlap, but don't appear to be attached by nails,
bots or screws. One joist span is 3m the other 1m. At this point the
joists were separated by lightweight concrete wall blocks, cemented in.
As the blocks were taller than the joists they caused the bulge in the
floor. I presume their purpose was to hold the joists in place and
prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to
attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I also thought I might buy a mitre saw to get the correct angles on the
struts. For a custom angle these all seem to be electric. Is this an ok
choice

https://www.screwfix.com/p/evolution-r210cms-210mm-electric-single-bevel-compound-mitre-saw-240v/7277p

The main thing that matters with mitre saws is that they have a metal base, otherwise they often cut off angle. And the saw should cut the max size of timber you're using.

I can't imagine anyone sane choosing a nonelectric one these days.


NT

On 09/07/2020 12:28, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard floor
panels to rectify.

The joists below are split into two parallel sections. The divide being
over a concrete lintel, about 30cm wide. The joist faces touch each
other and have a 10cm overlap, but don't appear to be attached by nails,
bots or screws. One joist span is 3m the other 1m. At this point the
joists were separated by lightweight concrete wall blocks, cemented in.
As the blocks were taller than the joists they caused the bulge in the
floor. I presume their purpose was to hold the joists in place and
prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard metal
strut from the bottom face of one joist to the top of the next. So I
figure I'll cut wooden ones. This will still be a little tricky to
attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I also thought I might buy a mitre saw to get the correct angles on the
struts. For a custom angle these all seem to be electric. Is this an ok
choice

https://www.screwfix.com/p/evolution-r210cms-210mm-electric-single-bevel-compound-mitre-saw-240v/7277p



Use some 6x2 noggins, you can stagger so you can screw through to each
one, good fixing screws will allow you to pull some of the lean out
...but once wood has twisted it don't like going back.

On 10/07/2020 16:57, rick wrote:
On 09/07/2020 12:28, Pancho wrote:
I had a bulge in an upstairs floor and have removed some chipboard
floor panels to rectify.

The joists below are split into two parallel sections. The divide
being over a concrete lintel, about 30cm wide. The joist faces touch
each other and have a 10cm overlap, but don't appear to be attached by
nails, bots or screws. One joist span is 3m the other 1m. At this
point the joists were separated by lightweight concrete wall blocks,
cemented in. As the blocks were taller than the joists they caused the
bulge in the floor. I presume their purpose was to hold the joists in
place and prevent twisting.

These blocks appear pretty useless, the cement around the has crumbled
and so they don't seem to serve any purpose, apart from preventing a
catastrophic twist. I could just shave the top off the blocks and put
the floor back down, but thought perhaps it would be better to use
herring bone struts or noggins.

The joists are very slightly off vertical.

I only have access from above, which means I can't use a standard
metal strut from the bottom face of one joist to the top of the next.
So I figure I'll cut wooden ones. This will still be a little tricky
to attach the bottom end of the strut, due to the ceiling panel below.

Any advice, or is it a reasonable plan?

I also thought I might buy a mitre saw to get the correct angles on
the struts. For a custom angle these all seem to be electric. Is this
an ok choice

https://www.screwfix.com/p/evolution-r210cms-210mm-electric-single-bevel-compound-mitre-saw-240v/7277p



Use some 6x2 noggins, you can stagger so you can screw through to each
one, good fixing screws will allow you to pull some of the lean out
..but once wood has twisted it don't like going back.

Thanks everyone for the advice.

I removed the blocks and I went with 38mm x 63mm herringbone struts,
38mm x 63mm seemed to be cheap.

The joists were not just slightly off vertical they were warped too. I
didn't think I would be have been able to get noggins in tight.

Even with the struts I used a bit of gripfill to make up for the
warp/unaligned gaps. It made me wonder if smaller struts would have been
better. However, I couldn't get 38mm x 38mm as it was sold out and was
more expensive anyway.

On 10/07/2020 08:12, Brian Gaff (Sofa) wrote:
Kind of begs the question, why was it done that way? M;aye there is more to
the flooring than is obvious. Has the building been modified in some way,
or damaged by fire in the past?
Brian

This is original design. The house is a bit wider at this point, maybe
it was cheaper to add a little extra joist than to have two sizes of
long joist.

On 10/07/2020 12:24, wrote:


The main thing that matters with mitre saws is that they have a metal base, otherwise they often cut off angle. And the saw should cut the max size of timber you're using.

I can't imagine anyone sane choosing a nonelectric one these days.


NT

Although I have got one stored away in the workshop "just in case"