[JustAHack]

I bought a 1930s cottage that is 20x32. The house has trusses that span 20'. It has 2x4 rafters that are 24" OC - in MA -aka- snow loads.

I would like to sister 2x8s or 2x10s on the rafters and raise the ceiling about 1'. I would install 2x10s going horizontal. In essence raising the ceiling and giving the room a much more open feeling.

Would this be ok to do? I figured I could keep the supports that come down at like a 45 degree angle to the new raised 2x10. Would I need to add a new ridge board under the existing ridge?

Do you think that I can safely remove all the strapping too?

 

[ChuckTin]

A 1930s cottage with a truss roof? That doesn't sound right. Did you get "full disclosure" at sale?

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[mako1]

I'm wondering a few things like the poster above.Whay are all those trusses black? Fire ?Who paints their trusses?How will sistering the rafters give you more give you more room to raise the ceiling?
A better pic a little further back may answer some questions.

 

[Anti-wingnut]

A 1930s cottage with a truss roof? That doesn't sound right. Did you get "full disclosure" at sale?

The concept of a truss dates back hundreds of years. If you looked at the photo, you would see that it is indeed a simple site nailed truss. Just because something is not the modern factory made truss you are probably only familar with does not mean it is not infact a true truss.

To the OP:

Simply sistering the rafters will not under most circumstances solve the outward thrust at the top plate. Sistering will reduce some deflection of the rafters, but you will need some collar-ties or a new and very substantial roof beam. Something like this is doable, but you will need a professional for design. I think an architect could design this prescriptively, but a PE would be your best bet.

 

[JustAHack]

The trusses are dark... I am not quite sure why. The pic actually looks real nice... Whereas in real life... Not so nice.

To Awing- thanks! So if I understand... I would need a new ridge beam? What is up there is a 2x4 if I recall.

As best I can tell.. The house was built in the 30-40s and then in 1990 someone re-informed it... See next pic. Note the original vertical studs in dark brown and the horizontal studs installed in the 1990s. At that time, I guess they added the strapping and sheet rocked the ceiling. Do you think it would be ok for me to remove the strapping? Or maybe put some strapping on the other side of the 20' cross member? Maybe 3-4 rows of strapping versus every 16".

If I understand... The 20' cross member rests right on the walls... So the walls are carrying the weight of the roof... And the 45s just provide some deflection onto the 20' cross member that carries the weight. I assume the new ridge beam would carry the opposing weight of the rafters on either side of the roof transferring down to the walls then?

 

[Oso954]

If it was mine I would just rip all that strapping down. Vacuum or otherwise clean the trusses and the underside of the roof deck.

The building was built to have the trusses exposed. That's the reason they are dark. My guess is a dark stain rather than a paint.

The strapping was just added to hang the ceiling. It is doing nothing as far as structure, other than adding weight.

Once you get all the strapping down, it's going to feel more open. You might even decide that you don't need to do anything about the trusses.

 

[JustAHack]

I was actually thinking of doing just that. Simply expose the trusses and paint it all white. I don't think my town will let me not insulate though as we are a stretch energy code town. I like the idea of raising the ceiling 1', sheet rocking it and installing recessed cans and ceiling fans. The ridge is presently multiple pieces. It all comes down to $$$$.

 

[Daniel Holzman]

What you have certainly looks like site fabricated trusses. A truss is a structural element comprised of triangles. The individual pieces of the truss are considered pinned together where they join. Modern wood trusses are fabricated using gang nail plates, but older trusses were fabricated using plywood plates, and even older trusses, like the ones you seem to have, were fabricated by nailing the pieces together. Nothing wrong with that type of construction.

Simple trusses such as the ones you seem to have are only supported on the ends. The trusses exert vertical load only on the walls, no horizontal load. The individual truss pieces are either in tension or compression, but not bending. There are NO roof rafters in a truss, what you are calling a roof rafter is the top chord of the truss. A roof rafter in a stick built house has a combination of compression loading and bending, which is completely different than the top chord of a truss, which is in compression only, except under unusual loading circumstances such as wind uplift, when the top chord could go into tension, but never bending.

Trusses do not need ridge beam or collar ties, they just need to be supported laterally during construction so they don't fall over. Once the sheathing is installed, and the trusses are connected to the walls, the trusses are not going anywhere.

Raising the ceiling in a truss roof house is not a simple matter. You need to modify the trusses, which requires you to perform an analysis of the loading on the new truss system you plan to create. This is usually not a DIY exercise, it may be something a local engineer or architect could help with. If you do not understand the mechanics of a truss system, I strongly suggest you NOT modify the trusses yourself, unfortunate results can occur, including collapse of the roof.