Complete amateur in need of guidance on raising loft joists

[peacockharris]

Hi there. I've admittedly only been visiting these forums this last week but I hope you guys might be able to help me nevertheless. I've scoured the internet and this forum tirelessly and I can't find conclusive answers to my questions.

I've recently had my loft insulated under the government scheme and would like to raise the joists so I can put a floor over the insulation without compressing it. I don't need it to be strong enough for a room or to meet building regs, I just need a solid surface throughout the attic so we can easily store boxes and xmas decorations. Currently it is a sea of insulation on top of all our belongings (as we were advised, so the insulation wasn't compressed) and I've just had to peel large sections of it back to put the Xmas decorations back. I hope to never have to do this again!

In order to achieve the floor with the insulation underneath, the joists need to come up by about 10 inches and after spending around 3 evenings trying to work out what the consensus was about the sizes of batons.....whether they go on top of the existing joists........parallel or perpendicular....whether they'd put too much load on the existing joists/the ceiling beneath? etc I've come to the conclusion that for my own peace of mind due to less strain on the ceiling, it makes sense to have 'suspended' joists using joist hangers. I'd hopefully be able to utilise the large central beam (is that the right word?) running along the middle of the attic floor to hold them in place also.

My house is a 1926 Semi Detached house. There is one brick wall dividing us from next door and the rest is sloping roof.

So my questions:

1. Is installing the joists with Joist Hangers necessary? And even if it isn't, does it make for a stronger floor?

2. How can you even utilise Joist Hangers on the sloping roof side?

3. Might there be other ways of getting extra strength or stability for the joists? Such as utilising supporting walls underneath.

4. Concerning the large central 'beam' running centrally along the floor of the attic- can Joist 'brackets' or some sort of right angled attachment similar to a hanger (but upside down) be used on that to support the Joists as well?

Sorry for my ignorance of the correct terminology.

 

[Chri5]

Stilts are available for what you want to do.

 

[peacockharris]

Hi there Chri5. I don't know if you read my post fully, but those legs tick pretty much all the boxes for what I DON'T want to do

The strain would be solely on the existing joists (again I don't want that and that's why I've been looking into joist hangers to fix them to other supports to spread out the load)

I'm assuming that I would utilise the brick wall for joist hangers along with the central beam, and that then on the side with the sloping roof I'd need some kind of Joist mounts supporting the joists from below. This I assume would be on top of any supporting walls (I think the end wall where the sloping roof rests would be useless as the slope would prevent the joists from reaching it at the height that's required)

I'm not sure I'm explaining it very well but it makes sense in my mind

Can anyone come forward and confirm or even better, contradict this? This is all a learning experience for me, so I'd really appreciate it if someone could point out any flaws in my logic.

I have to stress that whilst this floor is not going to see much traffic or bear much weight, I'd rather err on the side of caution just for my own peace of mind.

 

[tony1851]

If you don't want to use the floor as a room, or don't need it to comply with Building Regs, what's wrong with the stilts he suggested?
Trying to support joists off the rafters is impractical.

 

[JohnD]

you want to have a floor for light storage, is that right? and you would like it to be 150mm above the tops of the existing joists because you want to retain the existing insulating value, is that right? And you don't have a budget is mind, is that right? And you won't be having groupls of people, or heavy objects up there, and you don't need it to be suitable as a habitable room, is that right? But you have a loading in mind which exceeds the capacity of the existing timbers, is that right? What is that loading?

If you confirm your requirements, I'm sure we can suggest somerthing to meet them.

 

[peacockharris]

Sorry, I didn't mean to offend anyone and I understand I've been vague. I'm just new to all this.

I am a little cautious and just want to make sure it's as strong as can be. There's nothing more to it than that. It's just for peace of mind. I also know someone who's specifically tried to dissuade me from going the cross batoning or stilt approach because their ceiling cracked in areas from excessive load. I don't know the details of what was being stored by him. I also know nothing about the strength of my existing joists or even how to determine such so I'd rather make doubly sure it's strong enough. I have no particular load in mind - I would just like to make it as strong as it possiblly can be within a £600-800 budget.


As for the statement of supporting the joists off the rafters, I didn't have any intention of doing this. All I wanted guidance for was using the vertical brick wall (which is between us and next door), the large central floor beam, and the supporting walls beneath to elevate it to the desired level.

If this is what you meant, and you still believe it's impractical, tony1851, please could you tell me why. I was under the impression that it was just a case of drilling in joist hangers or even just batons into the wall & central beam. And in the case of the other side (without the brick wall) utilising legs or stilts over the supporting walls so it's as well supported as possible. I didn't think this was an unreasonable or unrealistic idea, but I did come here for constructive advice and criticism, so if you think I'm being ridiculous, please tell me why. I'd really appreciate it.

 

[JohnD]

counterbattening will spread the load but will not make the total roof any stronger. When screwed down, with the decking, it will be a lot more rigid.

You can also lift the top quilt and put rigid foam insulating board down, with the ply or chipboard on top of that. There will probably be a display in your local DIY shed. The board is fairly expensive but the effort should be less and no new timbers required.

Knauf advertise boards for this application.

 

[peacockharris]

Thanks for the reply, JohnD. Is there any particular reason you recommend counterbattening? (which if I'm not mistaken is just battening on top of the existing joists at a 90 degree angle) I ask because this is what I've been concerned about the entire thread.

Also is there any particular reason you're discouraging me from the joist hanger approach? The reason for wanting to reinforce it with the hangers/brackets was because of my concerns I mentioned about not wanting too much load on the joists/ceiling underneath.

If you think it's a worse idea than just counterbattening, please could you tell me why you think it's a bad idea? I thought it would provide more strength (please correct me if I'm wrong) due to it utilising structural walls.

I'm getting very confused as I'm finding some threads that recommend suspended flooring (which my idea appears to be similar, if not identical to) yet in this thread, people seem to be dismissing it completely. I'm just trying to understand why.

 

[JohnD]

If you want it to be a habitable room, and to have your piano and hot tub up there, you will need large joists supported off the walls to meet building regulations.

If not then the expense is not warranted and you do not need such a strong floor to store the Chistmas tree and your collection of motoring magazines.

I am looking for a solution to meet your requirements.

 

[peacockharris]

Cheers. I'm only looking for something that's a little more reinforced than counterbattening, so joist hangers at a few quid each tops don't seem like a huge expense to me.

 

[freddiemercurystwin]

What is the span between the existing walls? What continuous length of joist could you practically get into the loft space?

 

[JohnD]

something that's a little more reinforced than counterbattening

how much weight do you need to support?

 

[dhutch]

You need to work out what you want, but if its just for some christmas decs, your fine, if you want to be able to jump about with five mates, ram it full of heavy stuff, golf clubs, furnature, etc, maybe not.

For what its worth I extended mine by running 3x2 parallel with the existing joists, raised to the required hieght on spacers, and then screwed sideways into the rafters to give some lateral stability before the floor was put down.

I would also in retrospect pay more attention to leaving sufficent ventilation space between the insulation and the floorboards if your boarding it as I have got issues with condensation on the underside of the floor.


Daniel

 

[jamiepds]

Hope you don't mind me adding,its a similar problem.my roof was tiled and not strengthened after changing from slate.this was done before we purchased the property.had a builder/roofer come and put in some beams diagonally,and attached via a frame in the middle.but this has really made a big loss of space as want to board it,and store things up there,put windows in and use as an unofficial room.more just a get away from it all room.was going to have vertical beams going down onto joist hung timbers outline I think they are called.would this work,what size beams soul I need,was thinking 8x3 two together so 8x6 the lengths would be around 17foot.the old joists have been really weakened and slight sagging so don't want to go onto this.but want the room /space back.is this idea safe. many thanks looking forward to reply

 

[jamiepds]

Forgot to ask,do I need planning or anything for this