Bolting together 2 x 2 by 4s

[UKG2024]

Hi,

Can anyone offer advice on this please?

I'm building a music room in my double garage. To achieve this I'll be building a room within a room. The interior room will be framed with 2 x 4. And 2 layers of plasterboard and wool within the frame used to attenuate the sound. The interior room will be decoupled from the exterior existing garage.

My question is about what size wood to use to span the interior room for the ceiling (from stud to stud)? The span will be 5m.

I'd like to maintain as much height as possible in the interior room.

Any charts online seem to allow for 50kg/m 2 and occasional walking on the beams (e.g. flat roof charts). This ceiling will need to hold 20 kg / m 2 (2 layers of plasterboard) and will never be walked on.

My question is - do you think 2 x (2 by 4s) bolted together appropriately (creating 4 x 4) at 600mm centres will be strong enough across the span of 5m to hold the 2 layers of plaster board (20 kg / m 2)? OR should I go for a larger stud / beam e.g. 6 x 3 ? This just seems like a large piece of wood for this purpose and I'll lose 2 inches of ceiling height.

Any advice is greatly appreciated.

Thank you
Gavin

 

[Jacob]

Hi,

Can anyone offer advice on this please?

I'm building a music room in my double garage. To achieve this I'll be building a room within a room. The interior room will be framed with 2 x 4. And 2 layers of plasterboard and wool within the frame used to attenuate the sound. The interior room will be decoupled from the exterior existing garage.

My question is about what size wood to use to span the interior room for the ceiling (from stud to stud)? The span will be 5m.

I'd like to maintain as much height as possible in the interior room.

Any charts online seem to allow for 50kg/m 2 and occasional walking on the beams (e.g. flat roof charts). This ceiling will need to hold 20 kg / m 2 (2 layers of plasterboard) and will never be walked on.

My question is - do you think 2 x (2 by 4s) bolted together appropriately (creating 4 x 4) at 600mm centres will be strong enough across the span of 5m to hold the 2 layers of plaster board (20 kg / m 2)? OR should I go for a larger stud / beam e.g. 6 x 3 ? This just seems like a large piece of wood for this purpose and I'll lose 2 inches of ceiling height.

Any advice is greatly appreciated.

Thank you
Gavin

They'd be strong enough but not stiff enough, they'd sag in the middle.
If you were to bolt them together then edge to edge would be better; giving 2x8" .
Probably OK but I'd just go for ceiling joists as per the charts. https://www.timberbeamcalculator.co.uk/en-gb/span-table/ceiling-joists
5m is a long span, 44x220 at 600mm ?

 

[Jameshow]

I would use 6x2.

 

[Spectric]

If you use fabricated joist to span the 5 metres you will gain height as they will not need to be as deep. Engineered joist like I beams are strong and stable and you could even fabricate them yourself.

 

[sammy.se]

I would use 6x2, and add some noggins. If you did use 2x4, and they sagged, you would lose some height anyway, while having a suboptimal structure.

 

[ChaiLatte]

Why do they need to span 5m?

Could you not support them at midspan from the structure above with suitable vibration/acoustic isolators (wires with springs in the middle)?

Use the 4" x 2" and bolt some 40 x 5 flat steel bar to the side of it for the middle third. That will stiffen it up considerably. Use 4" x 1" at closer centres with the steel bar bolted on. Put plenty of screws in the plasterboard to give it lateral restraint.

Using joist span tables is not sensible as they will be written with deflection as the governing criteria. You need a general beam analysis program. The applied load is a uniformly distributed one. If the joist spacing were 1 meter, the UDL would be 20kg per linear metre of beam. A 500mm joist spacing would be 10kg per linear metre.

If you can make a moment joint at the junction with the walls, you can reduce the midspan deflection a lot. That is how portal frames (every steel barn you see) work.

 

[sammy.se]

plus, do you intend to hang anything from the ceiling, e.g. to hold your music equipment in future? if yes, go for the 6x2

 

[Phil Pascoe]

I wouldn't trust 6" x 2"s much over five metres.

 

[simonridout]

I have used home made I beams, using two of 2400 X 300 mm 11mm OSB, with 50 X 25 X 4800 mm battens glued and nailed each side top and bottom. It could support my weight, 85Kg, mid span, without apparent deflection. Used similarly to your proposed use, to support a light weight ceiling only. Cheap and easy enough to build a test beam and see if it meets your needs.

 

[HOJ]

Using joist span tables is not sensible

Why would you not use the span tables for ceiling joist sizes, is that not their purpose.

If you can make a moment joint at the junction with the walls, you can reduce the midspan deflection a lot

For my education how/what would a moment joint consist of, on a timber ceiling joist to wall connection, are you referencing joist hangers?

 

[Stuart Moffat]

Gavin (OP), I was intrigued by your question as I have a son, 32 years old, who I have just helped move into a new house, and looks to me to help get the place how he wants it. We are both musical. He is nerdy about sound. I am not. One major attraction for him was a garage that had already been converted to another room in the house (enough of a change it required, and got, planning permission. But it is a cold room , and as he moved in a few days ago I have been dealing with other issues. But to change the old garage into a music room, there are two problems. One he wants a more or less anachoic chamber. Why is beyond me since he would add reverb to the result to make it realistic. The second is heat insulation. Any suggestions for material that would insulate both sound and heat?
Stuart

 

[ChaiLatte]

Why would you not use the span tables for ceiling joist sizes, is that not their purpose.

For my education how/what would a moment joint consist of, on a timber ceiling joist to wall connection, are you referencing joist hangers?

Ceiling joist span tables are calculated according to British Standards. He is making a room within a room, which is not subject to those standards.

See:

https://www.timberbeamcalculator.co.uk/en-gb/span-table/ceiling-joists?load=0.25&class=C16

In particular, the notes at the bottom: 0.25kN/m^2 dead load plus 0.9kN point load are in excess of his stated loading (0.2kN/m^2 and no point loading. That is 25% extra dead loading on its own). The governing criteria in the span tables will be allowable deflection (I think it is often span/360). For its purpose as a music room, perhaps a higher deflection could be tolerated.

A general beam program would give him the actual deflection produced by his stated loads at any spacing he chooses. That will either tell him the spacing he needs to adopt or the deflection with which he must live. If he sisters the joist with something (e.g. the steel flat), he can recalculate the I value, recalculate the spacing or deflection and make a choice on how to proceed.

The problem is the joist span tables are excessively conservative for his application.

A standard connection at the end would be simply supported (pin joint), so no bending is transferred from the joist to the wall stud. If it is possible to make a ridgid connection, so some bending is transferred, that reduces the bending at midspan, thus reducing the deflection. It might be as simple as the spiked plates with a coach bolt through them - then as the joist rotates as it sags, the stud rotates with it. An alternative is an L-shaped plate well screwed to both pieces. As above, the canonical model would be a steel portal frame (agricultural barn).

If there is space, cantilever the joists beyond the studs and bolt them down hard to the floor - that will introduce a hogging moment at the stud, again reducing the midspan deflection.

No-one who is speaking in this thread is taking seriously his desire to maximise ceiling height - look at the post saying "I made OSB joists that were 300mm tall" - that is three times what he is proposing. I am trying to suggest a path to achieving what he wants as close to the 100mm depth he desires.

Everyone is in agreement that standard solutions are not going to work here (5m span at 100mm depth is a big ask), so we have to explore non-standard options.

 

[eribaMotters]

I always thought the rule of thumb for span was take the distance and divide by two.

5m is a bit over 16 feet, so no smaller than 8x2, preferably 10x2.

Colin

 

[simonridout]

My apologies, I did not take in the desire for headroom. However it raises another question - what is limiting the height, presumably the existing garage ceiling or roof, can this be used to support the new false ceiling?

 

[Jacob]

Ceiling joist span tables are calculated according to British Standards. He is making a room within a room, which is not subject to those standards.

Arguable. Building Control would say not so. But why not anyway, there's little to gain?

See:

https://www.timberbeamcalculator.co.uk/en-gb/span-table/ceiling-joists?load=0.25&class=C16

In particular, the notes at the bottom: 0.25kN/m^2 dead load plus 0.9kN point load are in excess of his stated loading (0.2kN/m^2 and no point loading. That is 25% extra dead loading on its own). The governing criteria in the span tables will be allowable deflection (I think it is often span/360). For its purpose as a music room, perhaps a higher deflection could be tolerated.

A general beam program would give him the actual deflection produced by his stated loads at any spacing he chooses. That will either tell him the spacing he needs to adopt or the deflection with which he must live. If he sisters the joist with something (e.g. the steel flat), he can recalculate the I value, recalculate the spacing or deflection and make a choice on how to proceed.

The problem is the joist span tables are excessively conservative for his application.

A standard connection at the end would be simply supported (pin joint), so no bending is transferred from the joist to the wall stud. If it is possible to make a ridgid connection, so some bending is transferred, that reduces the bending at midspan, thus reducing the deflection. It might be as simple as the spiked plates with a coach bolt through them - then as the joist rotates as it sags, the stud rotates with it. An alternative is an L-shaped plate well screwed to both pieces. As above, the canonical model would be a steel portal frame (agricultural barn).

If there is space, cantilever the joists beyond the studs and bolt them down hard to the floor - that will introduce a hogging moment at the stud, again reducing the midspan deflection.

No-one who is speaking in this thread is taking seriously his desire to maximise ceiling height - look at the post saying "I made OSB joists that were 300mm tall" - that is three times what he is proposing. I am trying to suggest a path to achieving what he wants as close to the 100mm depth he desires.

Everyone is in agreement that standard solutions are not going to work here (5m span at 100mm depth is a big ask), so we have to explore non-standard options.

Chart says 44x220 at 600mm i.e. 2x9" nominal.
or 47 × 195 at 450mm i.e. 2x8"
He's not going to get anything much less than 6" to work. Is the difference of about 2" worth worrying about in terms of extra headroom?
I think it's a simple head down brain off decision. Plus noggins or herringbone struts between the joists.

 

[Phil Pascoe]

If you're trying to minimise the depth of the ceiling support, use something lighter than plasterboard. PIR?

 

[Jake]

As I understand it, this sort of double wall soundproofing often has rubber isolating the two layers of walls. Extrapolating from that, can you break the spans by suspending the inner ceiling joints midspan (or 1/3 and 2/3 span) from some sort of rubber hangers.

 

[mg123]

Hi,

Can anyone offer advice on this please?

I'm building a music room in my double garage. To achieve this I'll be building a room within a room. The interior room will be framed with 2 x 4. And 2 layers of plasterboard and wool within the frame used to attenuate the sound. The interior room will be decoupled from the exterior existing garage.

My question is about what size wood to use to span the interior room for the ceiling (from stud to stud)? The span will be 5m.

I'd like to maintain as much height as possible in the interior room.

Any charts online seem to allow for 50kg/m 2 and occasional walking on the beams (e.g. flat roof charts). This ceiling will need to hold 20 kg / m 2 (2 layers of plasterboard) and will never be walked on.

My question is - do you think 2 x (2 by 4s) bolted together appropriately (creating 4 x 4) at 600mm centres will be strong enough across the span of 5m to hold the 2 layers of plaster board (20 kg / m 2)? OR should I go for a larger stud / beam e.g. 6 x 3 ? This just seems like a large piece of wood for this purpose and I'll lose 2 inches of ceiling height.

Any advice is greatly appreciated.

Thank you
Gavin

Can you span the width rather than length of the building?

 

[Jones]

If you use acoustic hangers you can use less timber such as 3x2 and save headroom,if it's really tight use metal acoustic bars which are only 40mm deep. There's plenty of proven off the shelf solutions for sound reduction and they will all work better than making something up yourself. Using the right plasterboard and isolating fixings like acoustic bars and hangers is key .

 

[UKG2024]

Gavin (OP), I was intrigued by your question as I have a son, 32 years old, who I have just helped move into a new house, and looks to me to help get the place how he wants it. We are both musical. He is nerdy about sound. I am not. One major attraction for him was a garage that had already been converted to another room in the house (enough of a change it required, and got, planning permission. But it is a cold room , and as he moved in a few days ago I have been dealing with other issues. But to change the old garage into a music room, there are two problems. One he wants a more or less anachoic chamber. Why is beyond me since he would add reverb to the result to make it realistic. The second is heat insulation. Any suggestions for material that would insulate both sound and heat?
Stuart

Hi,

These guys offer helpful advice on sound proofing a room.

https://www.youtube.com/@soundproofingexpert777

The book to read for acoustic treatment of a studio room is:

https://www.amazon.co.uk/Home-Recording-Studio-Gervais-Paperback/dp/B01182HM9K


Hope it helps