Loft "room" floor load concerns.

[jaaaaamie]

Hi everyone!

I'm sick of the hassle from the girlfriend about playing guitar, and had an idea about making a room in the loft space to play in.

The house is a small (8m x 4m approx.), relatively newly built (and cheap) and semi-detached.

Money is an issue, and even if I did have enough it couldn't be a proper room as there's no space for stairs. I don't have enough to splash out on expensive acoustic paneling, so I was thinking of making a "room" within the space, using a sandwich of rockwool inbetween 12.5mm plasterboard supported with a woodern frame. The floor will also have a layer of rockwool inbetween plywood and plasterboard with rubber between the floor and the joists.

I think I will be able to get adequate acoustic resistance from my plan to meet my needs, but I will be sacrificing headroom, and adding a lot of weight.

My question is, will it be able to take the weight?

I have uploaded a quick image from sketchup, showing a line version of the structure.

Untitled

• jaaaaamie
• 14 Sep 2011
• 1

The joists are 600mm apart from center to center, and are approximately 35mm x 80mm. There is a wall which I am assuming is load bearing running at 90 degrees to the direction of the joists. It is not quite in the middle (3.9m one side, 3.5 other) When tapped it doesn't sound solid, but doesn't resonate as much as the other walls. It is also the only wall upstairs with a wall underneath it. Also, it would be impossible for them to span that distance.

There will be a fair amount of weight from the plasterboard, not to mention the addition of all my guitars and amps. If I keep everything within 1m-1.5m of the supporting wall, will I be alright? If not, what steps will I need to take to make it alright?

If you need anymore information just ask, and I thank you all in advance for your help.

 

[Static]

Chances are the roof trusses span the full distance of the house front to back.. I doubt the internal wall takes any loading (or at least when originally designed)..

But to answer your main question, No.. the trusses would have been designed for light storage only.. once you add all your additional dead load there will be nothing in the design for you guitar or you.. i highly doubt the trusses would fail, but they would deflect more than standard limits allow meaning you will get cracks appearing in your ceiling over time..

Do you have a garage? Or maybe a garden with a nice shed?

 

[ajrobb]

I agree with Static, unfortunately effective sound installation is heavy.

That said I used to have a 50 gallon CWS tank in the roof supported on 4 trusses when the house was built in 1978. Avoid putting anything on the joists as they will bend. In the case of the CWS tank, my builders ran extra beams supported by the bottom of the 'W' beams and then suspended the CWS on extra joists between them. These extra joists actually bent quite badly but they did not affect the ceiling below. (They were not warped as they straighten themselves out in the few weeks between taking them down and dumping them.)

In a truss roof the load runs as a compression load up the rafters from the walls to the apex then under tension to the bottom of the 'W' and then up under compression back out to support rafters bending carrying the tiles. Because the beams from the apex down to the bottom of the 'W' are in tension, a bit of bending load shouldn't effect them.

 

[jaaaaamie]

Thanks for the reply's.

Do you have a garage? Or maybe a garden with a nice shed?

I don't, I have absolutely nowhere else to play.

I suppose the first step in working out what measures would need to be taken, would to work out the total weight of the proposed room, and contents.

I suppose I will also go up there later and remove a larger area of the insulation roll to get a better look at it. I will also take some pictures.

The shorter span between the two outside walls is only 4m's, surely it wouldn't be too hard to attatch joists between the two to take some of the weight?

That's if the wall underneath isn't taking any!

Will post up some more info with pictures later.

Thank you again

 

[jaaaaamie]

Am I correct in that if the whole structure and contents came to 1000kg, and it was 9m2 would It need to support 111kg/m2?

I will be going up there later (before I have a shower) and will take some more accurate measurements and some photos. Will have to move a larger section of the insulation.

And the plasterboard of the ceiling below was attached directly to the truss's of the roof, does this mean there are no joists? Because if not, I'm going to have to see if its feasible to take the weight, or part of the weight by adding joists between the block walls.

Thank you again

 

[jaaaaamie]

Ok i've been up!

Top and Bottom Truss's are 35mm x 80mm
(Some of the "W" shaped truss's are 35mm x 70mm)

600mm centers

8 trusses in total

Total span of truss's is 7.5m approximately.

There wall I mentioned before that the truss's cross is a block wall, and its 100mm thick. Its 2.4m long (building is 4.2m deep) Therefore half the truss's cross the block wall, and half don't.

The truss's span 4m one side, and 3.55m the other side of the middle block wall.

Does this change anything?

Thanks again

 

[Static]

Trusses would have been designed to take a storage load on the bottom chord of 0.25kN/m2 which is 25kg/m2 .. therefore your 111kg is beyond the design by alot..
Either make it lighter or support it independantly

 

[jaaaaamie]

Thanks for your help.

If there was no wall underneath the span, I wouldn't even be considering it! However, I think the solution lies not with the roof trusses, but with the block wall that may or may not be taking weight from it. The 9m2 (2.5m x 3.6m) area will be resting almost centrally over the block wall, sticking out 1.5m one side, and 1m the other, and the block wall running over half the length of the "room, and the amp's and guitars will be stored directly above it.

Would I be able to support it by using the block wall as opposed to new joists running 90 degrees to the truss's attached in the side walls? Could I not use 2.5m long beams slightly larger than the trusses - 35mm x 90mm, (trusses are 35mm x 80mm), and make sure the weight is evenly spread over each side like a see saw?

I would take away too much headroom adding new joists, and it would probably make it too expensive for my needs (remember its only going to be a well soundproofed box in the attic, not a proper room)

Thank you again for your help!

 

[freddiemercurystwin]

What are you planning on doing up there to make it 1000kg?

 

[jaaaaamie]

Double layer of 12.5mm plasterboard, and some guitars, amps any myself. It probably wont be 1000kg, but would rather be safe than sorry.

I'm pretty sure its not going to collapse or anything, because of the block wall, but I don't want to make any cracks in the ceilings below.

Thanks again

 

[Morrisman]

A set of quality headphones and a mini amp will save a whole load of loft work.

And nobody will hear a thing when you are bending your favourite riffs.