Trussed roof for extension

[RichTeaBiscuits]

Hello

I'm just getting some pricing for roof trusses to put on my extension. I've received a quote that I'm largely happy with, except that I could use some pointers on how the new roof will be tied to the existing.

The roof direction on the extension is at 90 degrees to the existing, and will connect on the pitched side (rather than the gable end). The quote I've got includes the following items, and it's not clear to me what the application for each of them will be?:

Layboard 25.00x175.00 Saw2/4,200.00
Post 38.00x150.00 TR24/600.00 4/1,200.00
Ridge board 38.00x150.00 TR21/3,000.00
Valley ceiling 38.00x125.00 TR21/1,200.00 1/2,400.00 1/3,600.00 1/4,800.00
Valley rafter 38.00x125.00 TR22/1,200.00 2/1,800.00 2/2,400.00 2/3,000.00

Any pointers, please?

Thanks
Rich

 

[RedHerring2]

Ask the suppliers. If they want your business they'll explain everything.

I've just had a quote, and placed an order, for a 'wing' extension to the duo-pitched roof, with a hip end and the suppliers provided truss diagrams X 4, layout diagrams including bracing, details on joints, load calculations for BCO, and details on joining the girder trusses.

That sounds more like a cutting list to make up the trusses on site.

 

[RichTeaBiscuits]

hmmm, i did ask them and was told "the loose timber is to tie into your existing roof. we do not supply pre-manufactured valley trusses onto existing roofs as we cannot guarantee a perfect fit."

The drawings you have sound like those from the supplier I used last time, Howarth Timber in Gloucester. But is seems they have stopped trading (at least the engineered timber part in Glos) as the contact number no longer works and there's no reference on the web!

maybe someone could explain how to do the tie-in (note I'm not that bothered about ease of access from the old roof to the new, and I'm not planning on cutting the existing roof except for trimming back the eaves).

 

[RedHerring2]

Donaldson Timber Engineering in Derbyshire, was the company I used. But they maybe be a bit far from you.

I see from their web site they have depots in Oxford & Hampshire:

http://www.donaldsontimberengineering.co.uk/

I've tried to take a snapshot in Adobe to add the zoomed image but my Adobe has thrown a wobbly and the snapshot don't work anymore.

Basically, 35mm X 72mm noggin (I'll use 72mm X 47mm pressure treated) between the exisitng rafters to take what would be the bottom chord of the truss and fix in place with 300mm long 25mm X 35mm timber nailed (3.75 X 75mm galvanised nails) below the bottom chord along the exisitng rafter. But I'll just use a bit of batten 50mm X 25mm ('cos it's pressure treated).

And a tile batten fixed midway across the existing rafters between each truss. But you don't have trusses!

There is a footnote in the quote, about firring strips or packing might be needed to match the existing roof.

 

[noseall]

maybe someone could explain how to do the tie-in (note I'm not that bothered about ease of access from the old roof to the new, and I'm not planning on cutting the existing roof except for trimming back the eaves).

The existing roof structure will have to remain intact, bar from removing the tiles, lathe and felt.

You then fix lay boards onto the existing rafters onto which the new rafters will sit.

 

[theoldun]

They have sent you a cutting list of loose timbers to hand cut the fly in. No problem for us to do, but if you do not know hand cut roofs, then you will really struggle especially cutting on to lay boards.
What you want is a set of valley reducing trusses resting against a 25x50 thrust batten fixed to existing rafters. We strip top covering and leave felt and battens on and fit reducing valleys in between existing battens. Cut out felt and battens as required, fit valley noggins morning roof tiler turns up.
Send drawing to these people. Just up the road from you.
Donaldson Timber Engineering, Airfield Industrial Estate, Enstone,
Chipping Norton, Oxon, OX7 4NP
For the attention Ian Mathews, Senior Design Technician
We do all our roofs with them. First class service.
oldun

 

[RedHerring2]

Excellent bit of advice, old fella, about leaving the felt/battens in place and only fitting noggins when tiler is on site.
I hadn't thought of that and I was worried about maintaining weather proofing.

I have to echo your sentiments about Donaldsons, (Derbyshire) I've only used 'em twice and pleased with service both times.