laying a floor in the loft


hi.
I'm putting floorboards in my loft, as I got a load of really nice oak ones for free.
What's the best way to deal with wires that go over the joists? The ones on the floor that is.
I thought about cutting notches about 1cm by 1cm in the tops of the joists, but I though this might be a bad idea as it might weaken them. Is it better to drill holes and reconnect them, or rewire it so they go along the roof?
Also, I have some vague memory that it's a bad idea to put flooring all the way up to where the roof meets the floor as it obstructs airflow or something. Is this true? My carpentry is not great so the floor I've laid won't be exactly airtight.
Many thanks.
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philicorda wrote:

What are you going to do with the loft when you have laid the floor boards?
The reason for asking is that if you are putting these on top of the ceiling joists then these will not take a heavy load without bending and possibly collapsing.

Whatever you do, if the ceiling joists are only around 4" x 2" in section (or part of a roof truss) DO NOT notch these for cables as you are further weakening them and building in further problems.
If you must lay the floor, then it is better to drill a hole in the centre of the ceiling joists and feed the cables through (keeping the hole as small as possible).

That will be the least of your worries if you board the loft out on top of the existing ceiling joists/roof trusses and then use the loft as another room without giving due consideration to heavy reinforcement/new joists in many critical areas.
My most serious advice to you (especially as you appear to have little or no experience or knowledge of the imposed loads [this is not meant in a derogatory way]) is to leave this job well alone as it could well end in major structural damage and a rather large hole in your bank balance - the insurance company may well not pay out if a disaster strikes as the could claim that the damage was self-inflicted.
Brian G
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On Mon, 27 Jun 2005 00:56:43 +0100, Brian G wrote:

Organize all the stuff that's up there a little better.

At the moment, the 'floor' is a load of old planks, chipboard that's reverting to sawdust, all kinds of stuff left by the previous owners. There was a load of carpet and junk up there that I've got rid of too, so hopefully the load will be a little less.

They look about four by two.

Ok. I think I'll not touch the cables, and not board that bit of the loft. The timber all looks pretty solid, but perhaps best left alone.

I have no ambitions of doing a 'loft conversion', just to make it a bit safer to move about the loft. I'm just screwing some floorboards down. It can't go that wrong, can it? :)

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philicorda wrote:

If it's just for storage of small stuff then the answer is no.
But if you completely board it and then become a little overconfident and suddenly decide to use it for a games room for the kids or fitting a train set etc, then you tend to forget the loads that are imposed until the ceiling bends (and I've seen one bending over a foot in the middle) and then the trouble starts.
All the best with the project.
Brian G
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On Mon, 27 Jun 2005 17:30:35 +0100, Brian G wrote:

Good. After reading your comments on load and a little googling I've decided to get most of the heavier stuff out of there and move it downstairs.
There is a brick wall on the floor below that runs almost parallel with the roof beam along the middle of the loft. I'm not sure if it actually supports the loft floor or not, so I'm getting a builder mate to have a look. (And a look at my 'craftsmanship' on the floor so far.)
If it does support it, I'll stack the remaining heavy stuff in the middle along that line. The loft is about 6 metres wide and 5 metres long along the axis of the roof beam.

Wow. Fair warning.
It's pretty horrible up there, the house is about 100 years old. I must say that in my small experience of diy, it's the most unpleasant job I've ever done. I'm using a filter mask, gloves and goggles because of the dust and rockwool, and I would not want anyone going up there ever without at least the mask.
The idea of making it a room had crossed my mind previously, I'll admit, but the reality is somewhat different. :) Best left to the pros.
Many thanks.

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philicorda wrote:

realistically, no, as long as you dont go stupid. But if you put a 6 ton waterbed in there... it may migrate to another room, removing any obstacles along the way.

You can pile boxfuls floor to ceiling on woodwork that size, as long as its not rotten. Larger woodwork is not used to increase breaking strength, but to reduce bending. Bending causes plaster cracking, then visible sag, then bowing, its long down the line that you get to collapse.
The oak floorboards will increase strength and stiffness if you screw them down.

they do.

not really. If you put 1:1 scale trains in it, then youd have a problem :) Not otherwise.

Well... youd need some more strength on the floor structure for a habitable room, plus various other requirements.
NT
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snipped-for-privacy@meeow.co.uk wrote:

Erm! That's not quite true really is it? You CAN pile 'boxfuls' to the roof rafters (not ceiling) as long as they are somewhere near the supported ends of the ceiling joists or directly over a load-bearing wall - but try doing that in the middle of a large, unsupported bedroom ceiling and the 'stack of boxes' with a relatively small footprint will rather quickly put and end to any bedroom activity below for a few days.

True, but but it will not appreciably increase the load-bearing capacity of the ceiling joists.

Possibly, but don't take that at face value. Check that the wall actually goes right down to a solid base on the ground floor and is not just resting on the bedroom floorboards.

It's the way of folks that they just don't stop there. They will build heavy tables to support their 'little' trainset and landscape features, then they'll want a couple of chairs to sit on, some extra storage units or even a small bed so the nippers friend can 'sleep over' and suddenly the weight becomes......

Inserted floor joists at least 8" X 2" A method of introducing natural light into the room - Dormer or Roof Light Repositioning of water tanks Removal of some of the roof/ceiling strutting probably having to cut and then reinforce the roof purlin(s) Insulation of the underside of the roof rafters against heat, cold and noise from falling rain Noise insulation to the new floor Installation of a permanent means of access to the room Compliance with the various building, planning and fire regs - along with Part P now A method heating the room Etc, etc, etc
I don't really wish to be pedantic or pour cold water on enthusiasm, but remember, normal bedroom ceiling joists are not designed to take anything much more than the weight of the lath and plaster - or plasterboard and skim - that they are covered with on the underside and if major works are envisaged - get the professionals involved every time -even if it is only to design what you want, calculate the loads and then get building reg approval/planning permission so that you can D-I-Y the job if you have the knowledge and confidence.
Brian G
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philicorda wrote:

realistically, no, as long as you dont go stupid. But if you put a 6 ton waterbed in there... it may migrate to another room, removing any obstacles along the way.

You can pile boxfuls floor to ceiling on woodwork that size, as long as its not rotten. Larger woodwork is not used to increase breaking strength, but to reduce bending. Bending causes plaster cracking, then visible sag, then bowing, its long down the line that you get to collapse.
The oak floorboards will increase strength and stiffness if you screw them down.

they do.

not really. If you put 1:1 scale trains in it, then youd have a problem :) Not otherwise.

Well... youd need some more strength on the floor structure for a habitable room, plus various other requirements.
I suppose you realise you can glue and screw 2x2 on top of the 2x4 if you want to bring it up to the standards of the other floors, ie waterbed proof it.
NT
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On Tue, 28 Jun 2005 11:19:39 -0700, bigcat wrote:

Interesting.

I'm about half way done across the floor now, and it does feel much sturdier. I'm using 5cm quite thin woodscrews as I don't want to risk splitting one of the joists.

It's more some huge boxes of books and magazines I'm worried about.

Now you tell me, after I've laid half the floor. :) Sounds like a lot of work though.

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I've been doing exactly that over quite a number of weekends and I can tell you that it IS a lot of hard work ! I had to extend the height of the timbers not only to provide me with a bit of extra strength but to enable me to put a reasonable amount of insulation in between, compared to the < 20mm of filthy, vastly irritating loose lay rockwool previously installed. The hardest part was clearing up all of this rockwool to give me a clean working enviroment and giving myself enough space to work eg: cutting timber, tool placement and cutting & laying insulation. The insulation was perforated into three sections, of course none of the sizes of pre-perforated insulation matched any of my timber spacings :( Three quarters of the way through the job now, bloody hot up there but the space it has given me will make all the sweat & toil worthwhile. I'd keep going with what you're doing and just spread all your boxes about and try to put the heaviest ones either over a support wall or near the end of a timber, good luck.
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