Loft truss bracing

[Dave Baker]

My new ( to me) bungalow is approx 55 feet x 30 feet, built 20 years ago and about exactly the same dimensions as a friend's bungalow in the same area. My loft is a spiderweb of horizontal wooden beams and further bracing structures joining the sloping roof trusses on each side about 3 feet above ceiling level meaning you have to crawl under them everywhere and it's useless for storing stuff with easy access. I'm told the previous owners removed all the horizontal bracing to make it an open space but the surveyor who looked at the place when they advertised it for sale told them to put them all back again.

My friend's almost identical bungalow has a fully open loft with no bracing beams so you can walk around in it, store stuff easily and get to the cold water tank without undergoing an assault course.

So what determines whether such intrusive bracing is is either necessary or recommended and how do I decide if I can just take it all out again? I imagine the only physical constaints will be the size of the sloping roof trusses and whether they can withstand any potential load ( snow or wind perhaps) that might be placed upon them.

[harryagain]

In days of yore roofs were constructed on site using rafters and purlins. Needed skill and time (Weeks). (This is the one that leaves lots of space.)

Nowadays roofs are made off site in factories using trusses. The trusses are delivered and can be erected in a day for your average house, Also they use lots of small pieces of wood which is cheaper & less wastefull. So it's all about money. Many early trussed roof were absolute shit, these are the ones you see that are sagging in the middle of the ridge.

If you were to remove anything, there is a good chance the roof would collapse, there is little reserve strength.

If parts have been removed in the past and replaced there is a good chance your roof is f***d because I don't see how these bits could be put back properly. The trusses are assembled with plate/gang nails, hydraulically pressed into place in the factory. Only a half wit would tamper with them.

You need to get this checkedout as a matter of urgency.

[harryagain]

Bit here on the topic of roof trusses. Virtually all new buildings have them nowadays.

[The Natural Philosopher]

welcomne to 'my roof was cheaper than yours'

Its necessary becuse a multiply braced roof uses half as much timber.

and the factory made trusses are far less labour than onsite construction, overall.

If you hand build a roof,. its less labour to use more wood and not brace, if you factory assemble standrad trusses, its cheaper tpo use less wood and cros-brace.

The bracing is necessary.

if you want a roof space available take the whole roof off and build a new one

[Phil]

Do you really mean 'trusses' or rafters? 'Truss' has a specific meaning - prefabricated offsite, thinner timbers, nailplates etc (as described elsewhere on this thread). If it's actually a fabricated on-site kind of roof, you could have a structural engineer re-design the supports to be less intrusive....

[GB]

Is your friend's house structurally sound, though? :)

It does sound as though you can take away the bracing and it all stands up for a while. The million dollar question is whether that while is 100 years or 100 days?

My guess is that your vendors lost a sale when somebody had the bungalow structurally surveyed, so they hurriedly reinstated the bracing so they could sell to you. Hopefully, it is all structurally sound now. One potential issue is the spreading load that tends to force the walls of the house apart. (imagine standing on a stepladder where there is no bit of string joining the 2 halves together.)

[Rick Hughes]

would add that on a trussed roof, if you want clear usable space you have to design in Attic Trusses ... much heaving timbers but does give 'a room' I would suggest getting a structural engineer to look at roof .... you may also be able to get free advice from local BCO, some are helpful.

To remove any part of a Fink roof truss seriously weakens a roof they are made with minimum timber sizes ... to keep costs down.

They can be altered, but would need a Structural Engineer experienced with roof design.

[Rick Hughes]

The big problem with removing bracing is that the load on the rafter line can cause rafter to start deforming - in truss design this is constrained by angled braces at 1/3 points (typically) If rafter flex this then alters the loading on walls. Trussed roof design in general allows for vertical loading onto wall plate ......i.e. all force is downwards thru the wall to foundation.

If the bracing is removed without appropriate design change (such as load bearing purlins) the load can then be outwards ... and walls are not built for that loading - can bulge & then fail.

An oft used solution is a horizontal purlin to transfer rafter load to purlins, these are for example built into gables to transfer load vertically downwards .. or have vertical load bearing timbers to transfer load to other load bearing walls. In effect creating a cut-roof. It's all about getting load to be vertically downwards ... walls are good in compression. (avoiding spreading load mentioned earlier in thread) There are ways to resolve - you need to get an engineer to taker a look.

[meow2222]

Less wood, quicker build, less cost all round.

I expect its possible to convert them to almost traditional by gluing & scr ewing on additional wood, after removing the bracing - obviously not all at once :) You get to choose whether to design what you want, using the regs minimum dimensions, and take it to someone qualified to check & hopefully s ign off.

NT

[<me9]

When Iwas investigating the same I was directed to the Timber development association (IIRC) website for information on TDA trusses. A google on the latter will probably reveal what is required.

Try