Loft conversion........sort of

[meditatinghamster]

Me and my wife just recently bought our first house. Only been in four months and we're looking to utilise to loft space. Really disappointed about limitations we've discovered but we're determined to make the most of it. We want to use it as an office room.

Age: 85 years old
Type: Stone end terrace.

Floor beams are 4cm x 7.5cm with 37cm space in between them.

Roof joists are 5cm x 7.5 and with 36dm space in between them

Height from the floor beams to the central roof beam is 173cm.

Purling dimensions (I'm assuming the purlings are the massive beams running along the sides) 27cm x 7.5

We realize that the height doesn't meet the regs for it to be an official room, and as it's an end terrace we can't get the roof raised. No one would be sleeping in there and it would be an office room only with one large velux. We don't care about making any kind of profit as we plan to stay here for may years and just want to max out the space potential. We can get 328cm x 400cm of useable space if we can do it, and that's not including any custom drawer space under the purlings!

The floor beams are worrying me though, as this room would be regularly used and I can't think of how on earth I could strenthen the floor beams without getting them completely replaced with bigger beams which probably isn't possible due the limitations of it being an end terrace etc..

I would really really really appreciate any advice anyone could give me on what to do. It would be a damn shame to leave it as storage only.

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[GoingDigital]

Yes the joists are to thin for any serious use, a very common issue as they were only ever intended to hold the celing up. What I have done is create a new floor in our house using 2"x6" (47x150mm) timber. Although still not officially good enough for a room, it is perfectly adequate for my liking without raising the floor to much. In our case there is a supporting wall in the center of the loft so the maximum unsupported span is 2m.

I have basically put a length of timber on joist hangers from and to end of the loft so that the weight is taken on the walls not the existing joists on each side under the purlins, parallel to them. I have then attached joist hangers all along this timber beam that are suspended 1" (25mm) above the existing celling, between the existing joists. This means that when the floor deflects a little it doesn't touch the plaster of the celling below.

Basically leaving the existing celling joists with no additional load on them.

Hope that makes sense.

 

[agbagb]

Good advice from GoingDigital.
Only one thing 2" x 6" is more than OK at 2m span. BC approved 4" x 2" at 450mm centres 2m span on my loft convesion.

 

[meditatinghamster]

Thanks to both of you for your advice on that, the option you've mentioned will no doubt be the only real solution I have open to me.

The fact that you've said the beams you've put down run parallel to the purlings must mean that the walls you'r talking about are the gable end and the opposing wall (chimney side)?

Does this mean that you've got the weight of the new floor held essentially on four points on the walls, i.e two where the beams rest on the gable end wall, and two going into the wall on the other side?

If so, isn't this putting loads of strain on the two end walls to go to 4 points of beam rest as opposed to the floor resting on 30+ joist wall rests on the side walls (eves)? The house isn't detached so it makes me wonder if I'd be legally allowed to put any extra strain on the ajoining wall.

Really sorry if I've understood this wrong. Building isn't my strong point as you've noticed!

 

[agbagb]

I used steel beams, yes, parallel to purlins. The section of these has to be calulated to take the load. Yes, mine are on to the party wall at side and Gable wall at the other. Loading on just 4 points is normally OK, with a pad stone ie. engineering brick transferring the load to the wall.

You should get a Party Wall Agreement signed with next door.

I think you would be wise to get proffessional advice before doing anything, it will give you piece of mind in the long run.

Andy

 

[GoingDigital]

Yes that is correct the wight of the new floor is on 4 points 2 on either end wall. The wall is a structural wall and is solid so it can take the wight where as the existing joists will just flex and the celling crack. Most houses have a central wall that is a supporting wall that divides the front and back rooms. Although sometimes the two downstairs rooms will have been knocked into one it is still a structural wall as an RSJ will have been installed to take the wall above.

Your new joists will straddle this wall so some of the weight will be taken there.

 

[GoingDigital]

As andy says if you were doing a proper conversion you would normally install steel supports. That would be required by building regulations along with calculations showing that the weight has been accounted for. You would also need to install a stair case, a fire door on all 1s't floor rooms and on the stairs to the loft. You would also need to ensure that your celling was fire rated so that means installing chicken wire over your existing celling as it is lave and plaster, and finally you would have to install a window that opens fully as a means of escape.

Now I'm guessing that you are not wanting to go to those lengths as you don't intend using it as a bedroom and would rather just make it strong enough for the new load. If that is your aim then I have found the way I have done it to be adequate. I have used heavy duty joist hangers on the wall. They are Z shaped there is tongue that is put between the mortar so that the wight is transferred onto the top of a brick.

It is a grey area if you need to notify the neighbor or not. As the party wall act requires you to notify if you are doing anything to alter the structural integrity of the wall, for example removing a brick to install a steel girder.

However you do not need to notify if you drill holes that go no further than half way through the wall to install things like shelves or a TV bracket for example. I would say that drilling a row of 6 holes in the mortar to insert a joist hanger that extends 50mm into the wall would be no different to hanging a heavy TV bracket on the wall.

 

[meditatinghamster]

Thanks for you're advice, I really appreciate you both taking the time to explain what you did. It's certainly put a smile back on my face as I know it's do-able. Some brilliant solutions.



I'd better have a look and see what supporting walls I have, it's something I haven't looked at yet!

 

[meditatinghamster]

OK, as stupid as this question my be, I'll kick myself if I don't ask and it turned out to have been possible.

Is is possible to raise the roof on an end terrece? I would assume the answer would be absolutely not because of the fact that you're joined to another house.

 

[GoingDigital]

Would be difficult but not impossible.

It would need planning consent as it would be altering the roof line and you would need to agree with your neighbor via a party wall agreement. The party wall would then be extended higher and a flashing seal put on the join between the end of their roof tiles and the wall.

You will see this arrangement on terrace houses that are built on a hill so the roof can not be in-line with the next house.

 

[mikric]

How about a dormer

 

[agbagb]

Another idea to consider, lower the upstairs ceilings. If you can loose 300mm of ceiling height and handle the disruption you could gain about 250mm in the loft. If you had a dorma as well it could make a practical room.

 

[meditatinghamster]

Would be difficult but not impossible.

.

Thanks goingdigital that's positive to hear.

Dormer is always the nicest option but velux is more affordable. Plus, a dormer needs planning permission from what I understand as your actually changing the volume of the house. I don't think you would get planning permission for a dormer if you didn't meet the regs for an official loft conversion, and of course mine wouldn't because of the lack of height.

Lowering the ceiling would be major and I'd feel like a hobbit . It might take me a while but I'll definitly get there one way or another.

You guys are stars. Thanks for the advice.

I'll keep posting piccies as I do more.

 

[Shytalkz]

You've got a certain percentage increase in volume of the property within which you don't need planning permission for a dormer, if this is kept on the back slope (and you're not in a conservation area, or a listed property). Planners don't concern themselves with the minutiae of building regulations.

Untitled

• Shytalkz
• 4 Mar 2009
• 2