Can I raise my joists?

[John Seed]

I pulled down a sagging ceiling in one of my bedrooms at the weekend (as one does). Above it, the joists spanning the room are bowed and need replacing.

The joists are nailed into the rafters beneath the oak beams that run the length of the house on either side (they are not attached to the beams).

What I would like to do is replace the joists with ones above the oak beams (to expose the beams and create more space in the bedroom).

Bad ASCII art of the side view follows.

What I have (The O's are the oak beams); /\ / \ / \ /O O\ /----------------\ / \ | | | | | |

What I want; /\ / \ /________\ /O O\ / \ / \ | | | | | |

I have 2 bedrooms in this elevation with a brick wall in the middle (upto the height of the oak beams). The walls are stone to the height of the beams with brick above. A brick extension runs off a hip in the middle of the house

The joists are 3"x1 1/2", the rafters are 3"x2", Both are about 10' in length.. They are spaced about 1' apart along the roof.

Can I do what I want? Is there a good book? Is is diy or do I need an expert?

Any other information that I should post here?

Thanks,

John

[Andrew Gabriel]

It may not have been apparent, but the joists are nomally rather structural -- they stop the roof spreading (rafters doing the splits) and sliding off the wall plates (your oak beams) or pushing the walls out with the weight of the roof.

[Set Square]

It's probably ok, if the oak beams are fully supporting the roof. However, there is a possibility that the joists are an integral part of the structure, and are required to prevent the roof from spreading.

You would do well to consult a structural engineer before removing them.

[Christian McArdle]

It looks possible to me, but you need to get a structural engineer to calculate it. In particular, the joists may currently be used to reduce spreading loads from the roof. It must be ensured that the new joist position with less leverage is still sufficient for that purpose. Even if not, there's probably a way through, such as using hidden metal rods or flitch beams or something.

As to whether the work is DIYable, that depends on your experience. Personally, I'd get a builder in to do the structural stuff, but would probably put up the plasterboard, insulation and electrics myself. (I'd get a plasterer in to skim it).

Christian.

[Dave Plowman]

I'd certainly get in a structural engineer. Shouldn't cost a fortune.

[John Seed]

Excellent responses, thanks.

Any recommendations for a structural engineer in Cheshire/Staffordshire/Shropshire?

Thanks again,

John

[Michael Mcneil]

Don't be silly. Recommending a use of them is not the same as having ever used them.

The oak -if oak they be, are purlins. The wall plate rests on the wall. The joists pulling the rafters together will occur above or below the purlins but the way the rafters bend with resultants will change.

Instead of tending to arc out they will tend to arc in. Getting good photos before you do the job will not only get you more confidant help but provide you with a record of stability over the years you remain there.

Whatever you decide, there was something already wrong with the building when you had to pull the ceiling down. I suspect a previous owner did something non-U with the roof. Get lots of lights in there and a good photographer.

[G&M]

What is the age of this house. Roof design has changed over the years and the places where forces are applied changed with it. I've done something with a very similar end result in my house and it looks fabulous, but the joists run parallel to the purlins so there was far less problems.

The main problem with modifying your arrangment is that the stresses on the new joints will be higher than the current arrangement. Also there is unfortunately a possibility of the roof moving as the new arrangement settles causing some work to be needed there as well.

Do you REALLY want to do this ?

[John Seed]

I'm guessing at least 150 years, though I think the roof (except the beams) is 20th century

Only if it's not TOO EXPENSIVE.

Thanks,

John

[John Seed]

Obviously, I'm just assuming oak.

OK, I've got "some" photos;

what's my next move?

Thanks,

John

[geoff]

In message , John Seed writes

Post them somewhere that doesn't require the viewer to log in ?

[Michael Mcneil]

A bungalow I think. Make sure the family gets out before that move takes place

[John Seed]

I hadn't clicked the "public" button;

[Set Square]

[RichardS]

oh, I could see why - the OP just wants to expose the purlins, not necessarily the whole roof space. Would give additional height to the bedroom as well. Presumably the exposed rafter ends would be covered and made good with plasterboard.

What puzzles me is why the joists have sagged - is this likely to be just the weight of the ceiling pulling down on them? I thought that ceiling joists would normally be in tension - keeping the rafters from spreading and maintaining the integrety of the walls. The purlins should presumably supported at each end by the walls, but there couldn't be any chance that these joists are, for some reason, taking the weight of these purlins, causing them to sag? If that was the case then something seems to me to be very wrong, and removing the joists could have very serious short term consequences!

In any case, this is non-trivial stuff potentially affecting the structural stablility of the house, and if I was the OP then I'd want to get the (paid) advice of a structural engineer as to whether it is possible to proceed, and if it is then the specs for the new joists and how they should be fixed to the rafters.

Armed with this info I don't see any reason why a competent DIYer following proper practise for the work couldn't tackle the job...

-- Richard Sampson

email me at richard at olifant d-ot co do-t uk

[geoff]

In message , John Seed writes

Honest opinion ? forget it.

[Rick Dipper]

I am using Alun Jones in Mold, I have been happy so far. I know he goes out to those areas.

As you are likley to be into Building Regs teritory, this won't be a cheep job. The building Regs guys cost you about 10% of the build cost, then you have a few hundered each for the architect to draw the pictures, and the enginner to do the sums .......

Rick

[Rick Dipper]

I would guess its gonna cost you a couple of grand, so decide if its worth it ........ Thats the next move

You might find the house is like mine, built without the cross members, so they can be removed. I can work this out cause of the age of the woods in the building, most are very old, the cross members are much newer, definatly not orignal. Also inside the loft you can still see the orignal celing going right up to the point. A bit of digging arround may yeald some results .......

Rick

[Michael Mcneil]

I don't think they have sagged. The level is not very long and the house is old. Rough sawn timber will shrivel a little between the knots. (I bet the high spots are a metre apart -just the length to throw that level out. Try a sting line underneath, right along them.)

Me too neither.

The joists are classically marked by laths used with lime mortar and that was the problem. They had come away from the grounds.

The purlins are 7 or 8 by 2 1/2s or 3's and will relocate the stresses very well when you shift the joists. You can reuse them.

Put battens along each edge to take the plasterboard. Make sure that they are exactly 400 or 600 gaps so that you can use the boards economically.

Put rockwool above each as you go.

Don't forget to make a loft hatch.

Put 1" ply under the purlins along the rafters tight up against everything and

Use longish ring nails or screws and tight fitted fillets top and bottom.

When you have finished; remember to clean, sand and paint or stain them all before you start.

[Michael Mcneil]

If his joists are running parallel to the purlins he had a good reason to use a structural engineer.

(He can sue the pants off the fool if he lives long enough.)

It won't cost you much more than the time you put into it and a few sheets of board and some insulation.

Edit to an earlier post:

If you put the plasterboard on top of the newly positioned joists, you will not need to bother with the battons.

Take the time to put a light in the roof space. Space the joists according to the board you use. Ply would be better than plasterboard as you can then utilise the attic.

If you put the ply under the purlins as suggested you might want to put lights in it, so put the wire behind them as you go and drill through for the feeds.