Cut roof instead of trusses

[2020c]

Ive a garage roof that ill be doing at my place in a few weeks. I was originally going to install attic trusses but with the cost of materials going through the roof, im now considering doing a cut roof instead.

My garage is 11m length x 8m width. The attic trusses where going to be 9x2s all over whereaa my cut roof will be 9x2 joists snd 6x2 rafters. A 9x3(or4) purlins.

The attic trusses or cut roof will be resting on a wallplate both sides and sitting on an 8x4 (or 8x8) rsj along the centre length.

The trusses where going to be spaced 600mm centers. Any cut roof ive worked on has been 400 or 450 centers. Looking online i can see cut roofs can be spaced 600 centers also, however can i still use 6x2s for tge rafters or would i need to use something bigger than this? Im at the pricing materials just now to see the difference in savings.

Labor is free with son and uncle giving a helping hand.

 

[noseall]

Ive a garage roof that ill be doing at my place in a few weeks. I was originally going to install attic trusses but with the cost of materials going through the roof, im now considering doing a cut roof instead.

My garage is 11m length x 8m width. The attic trusses where going to be 9x2s all over whereaa my cut roof will be 9x2 joists snd 6x2 rafters. A 9x3(or4) purlins.

The attic trusses or cut roof will be resting on a wallplate both sides and sitting on an 8x4 (or 8x8) rsj along the centre length.

The trusses where going to be spaced 600mm centers. Any cut roof ive worked on has been 400 or 450 centers. Looking online i can see cut roofs can be spaced 600 centers also, however can i still use 6x2s for tge rafters or would i need to use something bigger than this? Im at the pricing materials just now to see the difference in savings.

Labor is free with son and uncle giving a helping hand.

I doubt you'd be able to cut a roof and fix it for less than trusses, but who am I to argue.

Your rafter/joist spacings need to be worked out based upon your structural timber sizes and loadings. FWIW we NEVER space at 600mm if we can avoid it, even with trusses. But this is a personal (roof battens breaking) thing of mine. It sounds to me like you are just guessing your timber section requirements rather than engineering them.

 

[Dereekoo]

Deleted

 

[stevie888]

More info required: I assume you want to use the roof space fully if you're looking at attic trusses? How steep is roof? Rafter size requirement is affected by angle as well as length.

I would expect attic trusses to span 8m without central support but they will likely need a crane to install. Generally trusses will use less timber than cut and pitched simply because the individual members are working more efficiently. Also there is a lot less time and skill required in placing them


This needs engineering not guessing.

 

[2020c]

I doubt you'd be able to cut a roof and fix it for less than trusses, but who am I to argue.

Your rafter/joist spacings need to be worked out based upon your structural timber sizes and loadings. FWIW we NEVER space at 600mm if we can avoid it, even with trusses. But this is a personal (roof battens breaking) thing of mine. It sounds to me like you are just guessing your timber section requirements rather than engineering them.

19 trusses are coming in at 240£ or 250euro a truss and thats without the bracing. which is 4560£ or 4750euro. And bear in mind if im to install any roof windows more that the spacing between the trusses, ill need to double up the trusses at each side of the windows. thatll be another 4 trusses if 2 windows go in.

the cut roof materials are coming in at 1850e euro. Thats for 600m centers.
6x2s 6m 45 off for rafters
9x2s 4.2m 38 off for joists
9x2 6.6m 2 off for ridge board
4x2 2.4m 19 off for collars
9x2 4.8m 4 off for purlin
4x2 4.8m 9 off for under purlin.

Labor for both are free. Plus ill need a teleporter for errecting the trusses. building the cut roof, i have my own scaffolding and trestles, boards etc..

As for the nails, wall plate, straps etc.., ill need them for either trusses or cut roof so no need to price up here.

My own house trusses are spaced at 600mm which we installed 25 years ago. roof tiles and never any issues with snow loads or high winds.

Ill be installing flat roof tiles again on the garage.

 

[2020c]

head scratcher here with getting the measurements for my cut roof for my pitch and seat cuts but also looking at the truss plans , one is saying 40degree pitch and the other online roof pitch calculator is saying 42.22 with the same measurements! Unless the truss store has made the mistake!

 

[robinbanks]

So, it’s EUR1850 for 600mm centres, meanin it’s what.. 2K for the extra materials required for 400mm centres? It’s buttons, in the grand scheme of things

 

[noseall]

19 trusses are coming in at 240£ or 250euro a truss and thats without the bracing. which is 4560£ or 4750euro. And bear in mind if im to install any roof windows more that the spacing between the trusses, ill need to double up the trusses at each side of the windows. thatll be another 4 trusses if 2 windows go in.

the cut roof materials are coming in at 1850e euro. Thats for 600m centers.
6x2s 6m 45 off for rafters
9x2s 4.2m 38 off for joists
9x2 6.6m 2 off for ridge board
4x2 2.4m 19 off for collars
9x2 4.8m 4 off for purlin
4x2 4.8m 9 off for under purlin.

Labor for both are free. Plus ill need a teleporter for errecting the trusses. building the cut roof, i have my own scaffolding and trestles, boards etc..

As for the nails, wall plate, straps etc.., ill need them for either trusses or cut roof so no need to price up here.

My own house trusses are spaced at 600mm which we installed 25 years ago. roof tiles and never any issues with snow loads or high winds.

Ill be installing flat roof tiles again on the garage.

You seem to have forgotten the steelwork needed to support a cut roof of that size. Labour is rarely 'free'.

 

[2020c]

You seem to have forgotten the steelwork needed to support a cut roof of that size. Labour is rarely 'free'.

Steel for ridge or purlins? This did cross my mind although ive been on similar jobs where the purlins have been 9x2s 9x3s or double 9x2s and the ridge boards have been 9x1s or 9x2s. Steel rsj thou for under the joists or joists running into them.

Labour is free. My son and uncle will be helping. Uncle with the cutting and errecting of the rafters then me and the son will finish it.

 

[2020c]

So, it’s EUR1850 for 600mm centres, meanin it’s what.. 2K for the extra materials required for 400mm centres? It’s buttons, in the grand scheme of things

Ill double check this again on the software i have but im sure it was coming in alot more than just over 2k otherwise naturally id go for the 400mm centers.

 

[2020c]

You seem to have forgotten the steelwork needed to support a cut roof of that size. Labour is rarely 'free'.

Any response to why im getting 40deg and 42deg on the two pics above.

 

[noseall]

Any response to why im getting 40deg and 42deg on the two pics above.

A 42 degree roof with a going of 3760mm gives a 3385mm rise and not a 3412 rise.

 

[2020c]

So, it’s EUR1850 for 600mm centres, meanin it’s what.. 2K for the extra materials required for 400mm centres? It’s buttons, in the grand scheme of things

I tweaked it alittle and now upto 2k but once i go for 400 centers its now 750e more. see pics.

I was even thinking of going hollowcore to save on the steel, joists and ply or t&g osb but the hollow core is now upto 60e a sq meter installed so ruling that out now. On a tight budget, esp with the rising costs so trying to keep it to a min without the regs.

 

[2020c]

A 42 degree roof with a going of 3760mm gives a 3385mm rise and not a 3412 rise.

Truss manufacture must have made the mistake then when doing up the truss plan.

inside garage is 7200mm wall to wall. 100mm block, 100mm cavity, 100mm block on both sides and on the face of the garage is 200mm stone which takes the overall width to 8m then whatever soffit i want.