Convertible attic floor load bearing rating

Paremon2

Any help appreciated.

My questions:

• What are the Irish structural building regulations for houses built & sold with convertible-ready attics?
• What is the Irish regulation for load bearance of a non-convertible vs convertible attic? In the UK it seems to be 25kg vs 150kg per m2 https://www.diydoctor.org.uk/projects/loftflooring.htm
• As a new home purchaser what are my rights to obtain the basic info I need (load bearance, structural detail etc of attic floor) from a developer? Do/should I need to go through my solicitor?

My dilemna:

• I intend using a converted attic space/room as a home gym (with free weights up to about 100kg, a bench, barbell & dumbells, maybe a rack), a home office (standup desk, chair) & some furniture (sofabed, coffee table, bookshelf).
• I need to ensure that whatever I put on top of the subfloor (additional flooring layers + the above items) will hold without causing cracks or bowing to the ceiling below (1st floor bedrooms & hallway).
• I also need to contain as much sound within the attic area & minimise sound & vibrations travelling down to the floors beneath.
• For structural stability of the above items plus sound containment/travel/deadening purposes it seems (from my very limited knowledge & research) that the best & most economical way is to add the following to the existing 3/4" subfloor;
  1. Some form of acoustic material (e.g. an acoustic fibre product such as mass load vinyl, Tecsound or other).
  2. A 2nd layer of OSB fitted in the opposite direction to the existing subfloor.
  3. A thin acoustic underlay
  4. Laminate.
  5. Gym matts.
  I'm open to correction on the above layers. For example, would a good acoustic carpet underlay + carpet provide better noise reduction than laminate? Any advice welcome here.
• Obviously adding these 5 layers increases the load per square meter (e.g. by 30kg m2) on the structure before any free weights, furniture & people are added.
• I need to confirm the load bearance of the attic flooring as built/sold. However the builder I used for the conversion doesn't know & the developer foreman is not forthcoming with such info & quotes their contractor as being unable (unwilling?) to give this detail & only saying "it'll hold the weight of a normal bedroom".
• I think I need more specfics than this though as I don't know if the existing structure could hold what I intend. I've re-asked the foreman stipulating the importance of getting this info (even an approximate load bearing rating) & I've asked for details of the structure (RSJs etc) but I won't hold my breath.

Context:

• Newly built & purchased 3 bed semi-d.
• House came with a 'convertible' attic space. House brochure states; "homes structurally ready for attic conversion" & sold with a 10 year structural warranty.
• No details of what makes the attic space convertible were shared by the developer or estate agent pre or post closure (e.g. structure/materials/design, load bearance etc).
• I've since converted the attic space via a 3rd party builder to a room + utility room. This work included a new stairs, spray foam of attic space, 50mm warmboard vertical slabs, plastered walls & ceilings, velux x2, stud walls, plumbed & fitted radiator).
• I also got an engineer cert for the building regs & structural work (though i suspect it was just a paper exercise as it was an engineer recommended by the builders)

Flooring:

• The house was built & sold with an attic subfloor comprising a single layer of 3/4" OSB.
• No changes were made to this subfloor during the attic conversion.
• There's quite a bit of noise travel from the subfloor down to the 1st & ground floor.

Gumbo

Good luck with those requests!

Home gym should be on the ground floor, out the back or similar.
The constant use of 100kg weights in the same
Spot and constant placing from deadlifts etc will
Mean the whole house will be shaking everytime you use
Your attic gym.

Do it properly. Concrete base shed or similar.

With regards to your rights, you are not entitled to see any load bearing calculations, and design calculations etc your solicitor will
Get a cert confirming the house is in compliance with building regulations and that includes Part A (Structure).

Home gum wouldn’t be the normal residential use of an attic in my opinion.

Convertible attic means you bring in your designer to work out the alterations required to make it useable. Reason the developer didn’t do it was cost of bringing the rest of the house up to fire standards, ventilation standards etc that comes with 3 storey dwellings.

sydthebeat

"convertible attic" means its possible to convert in the future therefore its the owners responsibility to ensure its structural stability

Paremon2

Thanks for the replies. I subsequently got what it seems I need;
Got the roof truss contractor details from the developer, phoned them & they provided the roof truss spec sheet which includes the vertical load bearance (1.5kn /m2 or 152kg /m2).

Gumbo

Paremon2 wrote: »

Thanks for the replies. I subsequently got what it seems I need;
Got the roof truss contractor details from the developer, phoned them & they provided the roof truss spec sheet which includes the vertical load bearance (1.5kn /m2 or 152kg /m2).

Those figures are fine for everyday residential use.
People walking. Fixed furniture.
Wardrobes and storage.

But to add a home gym, I guarantee you will be repairing cracks in the ceilings for the rest of your days.

The additional impact loads from dropping 100kg weights and consistent use will eventually cause damage in my opinion.

Paremon2

Gumbo wrote: »

Those figures are fine for everyday residential use.
People walking. Fixed furniture.
Wardrobes and storage.

But to add a home gym, I guarantee you will be repairing cracks in the ceilings for the rest of your days.

The additional impact loads from dropping 100kg weights and consistent use will eventually cause damage in my opinion.

Thanks, I'm re-thinking this with a view to using the converted attic space for home office, sofabed, light storage, light yoga.

For sound containment/travel/deadening purposes it seems (from my very limited knowledge & research) that the best & most economical way is to add the following to the existing 3/4" subfloor;

Option A;
1. Some form of acoustic material (e.g. an acoustic fibre product such as mass load vinyl, Tecsound or other such a Green Glue which would weigh less)
2. A 2nd layer of OSB fitted in the opposite direction to the existing subfloor.
3. Low decibel carpet underlay (I have Tredaire Citra 11mm already, unused)
4. Carpet.

Option B;
1. Some form of acoustic material (e.g. an acoustic fibre product such as mass load vinyl, Tecsound or other such a Green Glue which would weigh less)
2. A 2nd layer of OSB fitted in the opposite direction to the existing subfloor.
3. Acoustic laminate underlay
4. Laminate 12mm
Total load = ~30kg /m2

I take it that with vertical load bearance of 152kg that either option A or B + the above furniture/usage would hold without issue, particularly if I used Green Glue instead of MLV, correct?

If so, which of the two options would give the lowest impact noise & airborn noise do you think?

Metric Tensor

1.5kN/m2 is the standard imposed loading (called variable action these days) taken for domestic floor design in Ireland.

It's perfectly capable of taking beds, wardrobes, sofas, etc

The floor finishes are technically a dead load (called a permanent action in the eurocodes).

There's a chance the truss manufacturer has also included a dead load in addition to the live load. You could check that out with them if you feel like it.

Download TGD E - it's the technical guidance document for sound. It has a section on timber floors with regards to timber floors separating dwellings but you will get some ideas there for appropriate sound insulation. One of the problems you might face is not just the direct sound transfer through the floor but flanking sound around the edges and joints as well as sound travelling down the stairs.

Paremon2

Metric Tensor wrote: »

1.5kN/m2 is the standard imposed loading (called variable action these days) taken for domestic floor design in Ireland.

It's perfectly capable of taking beds, wardrobes, sofas, etc

Thanks, by standard imposed loading for domestic for design in Ireland, do you mean for converted attics floors only or for first level floors also...I assume the latter... (or would first level floors tend to have a higher load rating)?

The floor finishes are technically a dead load (called a permanent action in the eurocodes).

There's a chance the truss manufacturer has also included a dead load in addition to the live load. You could check that out with them if you feel like it.

These are the load stats from the roof truss contractor;

LIVE LOAD OUTSIDE ROOM: 250
LIVE LOAD INSIDE ROOM: 1500
LIVE LOAD PARTITION: 220
LIVE LOAD ON COLLAR: 250
DEAD LOAD ON ROOF: 685
DEAD LOAD ON ATTIC SLOPING CEILING: 250
DEAD LOAD ON CEILING: 250
DEAD LOAD ON ATTIC FLOOR: 250
DEAD LOAD ON ATTIC CEILING: 250
DEAD LOAD ON ATTIC ROOM VERTICAL: 125

Does this look like the attic would take the load of my intended use & floor structure in my last post?

Download TGD E - it's the technical guidance document for sound. It has a section on timber floors with regards to timber floors separating dwellings but you will get some ideas there for appropriate sound insulation. One of the problems you might face is not just the direct sound transfer through the floor but flanking sound around the edges and joints as well as sound travelling down the stairs.

Will do, thanks again.

Metric Tensor

Paremon2 wrote: »

Thanks, by standard imposed loading for domestic for design in Ireland, do you mean for converted attics floors only or for first level floors also...I assume the latter... (or would first level floors tend to have a higher load rating)?



These are the load stats from the roof truss contractor;

LIVE LOAD OUTSIDE ROOM: 250
LIVE LOAD INSIDE ROOM: 1500
LIVE LOAD PARTITION: 220
LIVE LOAD ON COLLAR: 250
DEAD LOAD ON ROOF: 685
DEAD LOAD ON ATTIC SLOPING CEILING: 250
DEAD LOAD ON CEILING: 250
DEAD LOAD ON ATTIC FLOOR: 250
DEAD LOAD ON ATTIC CEILING: 250
DEAD LOAD ON ATTIC ROOM VERTICAL: 125

Does this look like the attic would take the load of my intended use & floor structure in my last post?



Will do, thanks again.

Only seeing this now.

I'm afraid most of it I cannot answer without straying into the realm of structural advice which is both not allowed on this forum and I wouldn't do anyway.

However - I can answer the question about the. 1.5kN/m2 - that is for all domestic floor loads. The code does not distinguish between ground, first, second, third, attic, etc.

wolfyboy555

https://www.boards.ie/discussion/2058130316/convertible-attic-floor-load-bearing-rating

OP did you go ahead with your plans for gym in your attic. I'd be interested to know as was considering something similar.

Mellor

I know it's an old thread. But for the same of correct information.

• I intend using a converted attic space/room as a home gym (with free weights up to about 100kg, a bench, barbell & dumbells, maybe a rack), a home office (standup desk, chair) & some furniture (sofabed, coffee table, bookshelf).

• I need to ensure that whatever I put on top of the subfloor (additional flooring layers + the above items) will hold without causing cracks or bowing to the ceiling below (1st floor bedrooms & hallway).

• I also need to contain as much sound within the attic area & minimise sound & vibrations travelling down to the floors beneath.

• For structural stability of the above items plus sound containment/travel/deadening purposes it seems (from my very limited knowledge & research) that the best & most economical way is to add the following to the existing 3/4" subfloor; (Acoustic material, OSB, Underlay, laminate, gym matts)

• I'm open to correction on the above layers. For example, would a good acoustic carpet underlay + carpet provide better noise reduction than laminate? Any advice welcome here.

• Obviously adding these 5 layers increases the load per square meter (e.g. by 30kg m2) on the structure before any free weights, furniture & people are added.

• Not a good idea in an attic. For multiple reasons, I'd go as far to say a terrible idea.
• It probably won't, and its not just bowing, the other risk is collapse.
• Very difficult to contain gym sound in light weight construction
• This is kind of ok, but Underlay needs to be thicker rubber and laminate is doing little should just be more ply or OBS. Top with gym mats. Improves one problem, makes another worse.
• Exactly, which means is even more likely to fail and hence a bad idea.

I'm station this as somebody who has designed many gyms. Private gyms, commercial gyms, and for professional sports teams. In industrially buildings, commercial/residential mixed use etc. Sound and structural issues are always a concern. The structural/acoustic build up we use is concrete slab, always.

The require load ins 5KN. You might get away with 3.5kn for a home gym, 1.5kN is nothing.

A load over 1m2 is spread across 2-3 joist. In a a gym, the weights are point loaded through the feet of users and equipment. If you bench press 100kg. There will be the weight, plus you bodyweight, plus the bench itself all going through the feet. Maybe 250kg on 2 joists (1m2). That's 2.5 KN already. Deadlifts will be heavier on smaller area. A rack is heavier again, point loaded on the uprights.

There are home gyms you could put in an attic. But not the above.

Bass Reeves

Just as an addage. 1.5KN/SqM is approx equivalent to 1.5 kgs/ sqCM.

The 150 kg dumbbell without beinh dropped (assuming it was landing lightly would 30-50 times that

Mellor

https://www.boards.ie/discussion/comment/121171332#Comment_121171332

Not really. 150kg is ~1.5kN. Structural loads are rated per m2 as standard. You can't simply convert to cm2 and say it's equivalent, it's an equivalent as a UDL, but not as a point load such as a weight.

The measurement is the load on the structure, not the pressure at the point of contact. A 150kg DB is the same as a 150kg person, which is basically 1.5kN/m2

Dropping a 150kg dumbbell from a height would add other forces. But I doubt there is a 150kg Dumbell in the country, OP certain isn't getting one into his attic. (for reference the 2023 Worlds Strongest man included a 150kg Dumbell, nobody lifted it...)

wolfyboy555

the area I have in the attic has 9 inch joists running across and then 6inch on top of them going perpendicular. Then OSB on top.

I'm not a bodybuilder so wouldn't be going near those heavier weights you mention of 100kg bench or larger dumbbells. Just was looking to do a small bit of bench, squats and dumbbells to improve strength and conditioning. Gym membership is expensive! The other alternative is my shed but that is raised off ground on blocks with OSB. I just thought attic would be stronger.

Final alternative would be to just keep going in the gym I suppose.

Mellor

https://www.boards.ie/discussion/comment/121181932#Comment_121181932

The 6" running across doesn't make the floors stronger, it actually makes it weaker it's more weight for the 9" to carry.

I'm not a bodybuilder so wouldn't be going near those heavier weights you mention of 100kg bench or larger dumbbells. Just was looking to do a small bit of bench, squats and dumbbells to improve strength and conditioning.

What do you bench press now? It would not be unreasonable to add 50% over a year or two of have a home gym. 100kg is not a very heavy bench tbh. Then add your bodyweight, and the weight of a bench itself, and you're easily looking at 200-250kg spread over a small. Squats would be the same story.

The other alternative is my shed but that is raised off ground on blocks with OSB. I just thought attic would be stronger.

The shed is likely simialr 9" joists, over a shorter span. Which makes is stronger. And if safer as it something does break, its only the shed. If you'd really rather the attic, it would be possible with careful weight selection. No barbells, no bench press, no squat rack or treadmill. Lower impact equipment like bands, kettlebells, rings/TRX

coconut2674

I know this is a slightly old thread, but curious OP how you got on.

I recently got a home gym set myself and have it in the spare bedroom. 120kg of weights and a rack - I only use it on rainy days when I can't get out to the gym, but this thread definitely has me considering moving them to the garden and storing them in a secure bunker, or clear space in the utility room.