Loft trusses

[Jonni]

Hi all,

I have just had a look into my loftspace as I'm interested in turning it into some sort of computer\play area. I'm not talking about habitable at this point just simple flooring etc.

You will see from the photo that there are trusses which in their current position render the space quite useless. The property is a council semi, quite solid, probably built 40s\50s.

Questions are as follows.

1) Difficulty level (1 (low) - 10 (tricky)) in repositioning trusses to allow workable space

2) Position trusses would have to be placed if moved? e.g. vertical near the edges or horizontally near the roof apex

3) Cost of having someone in to do only that (I would do flooring etc myself)

4) Time to complete?

5) Is this a fairly common job in the trade?

I am aware that before doing anything I would need to contact the local authority - this is just to give me an idea.

Photo:

Thanks in advance

Jonni

[Andrew Gabriel]

If I'm judging the size of that space correctly (about 5' high by

10' wide), I rather doubt those trusses are required at all. They appear to be transfering some of the weight onto a centre supporting wall, but the roof span looks to be tiny at that point anyway. Alternatively, if there is no supporting wall under the centre, they are supporting the ceiling (hanging from the rafters), but that seems unlikely in a house that old, with only a 10' span.

You need to get a structural surveyor to check the size and spacing of the rafters, with respect to the weight of the roof covering, and say for sure if the trusses are required or not. If something is required, you might be able to swap them for purlins at each side. Surveyor should also be asked to comment on max loading on the loft floor, given the size/spacing of the ceiling joists. You may find you can't actually put anything much up there without strengthening the ceiling joists, which will lose you headroom.

[Weatherlawyer]

What a stupid list!

To start with you want better photos.

Modern roof trusses are not like that -which may or may not be because they are not trusses of the modern style. However they might be early versions of the modern composite truss though, except that the timber is too new.

What are those cross pieces? And is there a ridge board -a 7 x 1 or something, down the middle of the top where the rafters meet?

What section are the actuall rafters? And how far apart are they? Measure from a side of one to the corresponding side of another and measure three or four. I'll bet they are in metric.

[Jonni]

Weatherlawyer wrote: > What a stupid list! >

Why is it "stupid list" Michael?, it is any more, or any less stupid than the questions you went on to ask me? - would someone with such a low level of understanding about this subject (quite obvious from my 'stupid list') be able to answer your questions?

Having done some digging I see that I should have expected that sort of response from you. Since you know all about trusses (and apparently earthquakes, weather and homophobia) - I'll give you some friendly advice, think before you type, you never quite know who you're responding to.

Speak to you soon.

[Brian G]

You cannot just 'remove' or 'reposition' those trusses, they are there to carry a load.

What you have to do is to cut 4 holes in the pine end and party wall (2 in each) and fit something like a 9 x 4 purlin on either side at the centre of the roof and fixed into the holes that have been cut out.

Fairly expensive! Remember though, if you are using it as you suggested, you cannot just lay a floor on top of the ceiling rafters, they won't take the loading without bending or possibly snapping.

As long as it takes.

Yes, and it really needs a professional to give you the necessary advice on loading calculations etc.

Jonni, please seek some professional advice on this, as this is a dangerous job for an amateur to do.

Brian G

[Jim Alexander]

Similar to a loftspace I had once and successfully converted. Same angled struts, slightly further apart. My rafters were 6"x2" and yours look similarly sized. My ceiling joists which became floor joists were also

6"x2", however I can't see the size of your ceiling joists. I got a structural survey through (or similar). That is the best investment you can make. If its do-able the report will tell you what you have to do. Might even be straightforward enough to diy. A few hundred pounds from memory. If your ceiling joists are 6"x2" I expect the project is do-able, if smaller I would expect you would need to add deeper floor joists. Not particularly difficult but it eats into your headroom. A lot depends on your ceiling joist support arrangement which you don't mention. A structural engineer would be able to tell you whether your rafters would need a purlin supported by your end walls or by a dwarf wall built off your ceiling/floor joists which is what I did.

If you are happy with the headroom its probably do-able, but you need a proper survey to tell.

Jim A

[Guy King]

The message from "Brian G" contains these words:

And anyway, you'll need to top up the loft insulation before you put the floor down. You seem to only have 4" which is half what's now recommended.

[keith_765]

They are not trusses at all. Just 4" x 2 timbers with a diagonal bracing to a centre ceiling beam, there is also a ridge board. The diagonal bracings take place of a centre under rafter purling. I'm surprised no one as mentioned the open boarded roof, not t&g, most unusual, in fact the roof carcasing is unusual. To use the roof space you would have to put in a quite substanual under rafter purling either in timber or steel, reinforce the ceiling joist before taking the diagonal bracings out and boarding the floor. An engineers report would work out the stresses and sizes of the material need. Council approval would probably need and to be notified if the property is still rented from them.

K. S

[John Rumm]

Well, it looks more like a traditionally joined roof to me rather than a trussed one. This makes things somewhat more doable.

A few questions:

What sizes are the timbers used for the: rafters, ceiling joists, and struts?

What is the approx span of the ceiling joists?

Is there a supporting wall coincident with the struts that run down to the centre of the span?

The most obvious replacement would be either to add a purlin (i.e. large horizontal timber running the width of the loft about mid way up the rafter span (with a single strut to a centre supporting wall), or possibly a dwarf wall a little below the mid span of the rafters that transfers the load to the floor. (assuming here that the struts you see are acting in compression supporting the rafter slope rather than in tension carrying the mid span of the ceiling.

You may need to uprate the floor (took two of us six days on my place). The superstructure changes would be quite simple if not adding dormers etc - perhaps a week for the basics. You can translate those times into money for your area!

Yo get insulation in, a velux perhaps, plasterboard etc say four to six weeks. This assumes you are still using a ladder for access.

common enough, although many builders will shy away from loft conversions because of the perceived complexities.

See if you get any more information from:

[The Natural Philosopher]

Look like trusses to me mate.

Anything with diagonal bracing is a truss...

They do a lot more than that.

I think you would in all probability have to replace or double up the rafters as well.

My gut reaction when looking at a loft like that is 'forget it'

It will never ever repay the effort involved, better to find a bigger house and use the money saved to buy it..

[Ian_m]

SNIP

You mean to do a conversion like this, easy just remove the beams.....