Calculating truss and other building materials

[nalle59]

We are replacing our roof completely and have quotes from carpenters to do the job. We have scale drawings of the roof and width and depth of the trusses .The carpenters do not want to calculate the timber needed does anybody know of company that can do this? I do not need to know the cost just the amount and size of timbers needed.I am able to do this but rather get someone else more experienced to do it as I am worried about getting it wrong.

 

[RedHerring2]

These are the people that I've used on two occasions for manufacturing roof trusses:

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

 

[nalle59]

Hi ,forgot to say we will have cutroof trusses NOT proprietory trusses so this company is no good for us.We need ALL the materials calculated not only wood so we can order them from builders merchants.We will happily pay for quantity surveyor to do it ,any suggestions?

 

[freddiemercurystwin]

Are these pre-fabricated trusses in which case the supplier will provide the calcs.

Otherwise is it a cut roof (made up of individual timbers on site) in which case you need to employ a structural engineer. If so have a google and phone a couple up and get some quotes. Usually a one man band type of chap will be cheaper.

 

[RedHerring2]

I don't have any experience of dealing with carpenters for this type of work, but having done a cut roof for a 5 m X 8 m workshop, duo-pitched with hip ends, I calculated all the sizes and amounts of timber using Timber Tables and pencil & paper. I'm a DIYer.

My comment is, if your carpenters can't estimate the amount of timber required for a cut roof, having been given the dimensions of the timbers required, I, personally wouldn't have a lot of faith in them.

Edit; Sorry, I've just re-read your first post and i see that you need the dimension of timber required. I initially read it that you had the depth of truss required, which to me meant the size of timber required.
Although, I'm not sure it affects my comment a great deal.
Timber Tables give you the size of timber required for given spans in given positions and situations.

Re-read your post again and I see that you think that you can make the choice of timber size required. Why can your carpenters not do this?

 

[jeds]

Can you not just calculate off your drawings? There are very few elements to a cut roof. Rafters, hip rafter and maybe purlins is about it really. Timber comes in standard lengths in 300mm increments starting at 1.2m up to 6.0m. Smaller merchants will only keep the popular lenghts - a larger merchant will keep more options. Just calculate the length of each element and then go up to the next standard cut length. If you have short hip lengths see if you can cut two or three from a full rafter length. That way you only need to order x number of one length. Also make sure you get the right grade.

 

[theoldun]

On a cut roof calculating size, length and overhang of rafters is very simple.
All you need is over all span of plates, rise or pitch.
Ceiling joists, binders and if required purlins, can be a little more complicated, and you need a layout showing length of building and internal load bearing first floor partitions in case you need one or two King Post or TDA trusses in amongst your commons.
If, as you state, you have scale drawings, these should give all timber dimensions.
If your scale drawings do not give this information any half tidy SE, architect, or architect technician should be able to give you this simple information.
oldun

 

[nalle59]

On a cut roof calculating size, length and overhang of rafters is very simple.
All you need is over all span of plates, rise or pitch.
Ceiling joists, binders and if required purlins, can be a little more complicated, and you need a layout showing length of building and internal load bearing first floor partitions in case you need one or two King Post or TDA trusses in amongst your commons.
If, as you state, you have scale drawings, these should give all timber dimensions.
If your scale drawings do not give this information any half tidy SE, architect, or architect technician should be able to give you this simple information.
oldun

Thanks for your message ,I have structural calculations from the engineer he does not do calculations for building materials .I can do scale drawings but do not feel confident to calculate the timber correctly.We have had carpenters giving quotes but they do not want to do the calculations.The timber alone will be about £5000 so do not want to make mistakes .I asked online quantity companywww.quantimate.co.uk to calculate all building materials and they quoted £90 to do it so might have to use them .Maybe worth so all the materials will be on the list so I can shop around .I no nothing about Binders ? Purlins yes ,Tda trusses? King posts? what are these? the size of the trusses 50mmx150 roof trusses building is 11m wide with cropped hipps so each truss at 400mm is about 26 trusses on each side I also need wood for the aslar walls etc.The trusses will be cut by the carpenters on site.

 

[RedHerring2]

Have you tried Builders Merchants? I think some will calculate quantity of materials from drawings and provide a quote for supply of all.

 

[freddiemercurystwin]

Oh I completely misunderstood I thought the OP wanted structural calcs!

 

[geraint]

We are replacing our roof completely and have quotes from carpenters to do the job. We have scale drawings of the roof and width and depth of the trusses .The carpenters do not want to calculate the timber needed does anybody know of company that can do this? I do not need to know the cost just the amount and size of timbers needed.I am able to do this but rather get someone else more experienced to do it as I am worried about getting it wrong.

if they cannot even work out the basics then i would not even let them on your property...

 

[hotrod]

Thanks for your message ,I have structural calculations from the engineer he does not do calculations for building materials .I can do scale drawings but do not feel confident to calculate the timber correctly.

You just need to do a take off from the drawings - if you've got scaled drawings it's pretty easy. Send me the drawings if you like and I'll take a look tomorrow - don't throw away £90! It's first year Uni stuff, but if you don't feel confident I don't mind helping you out .

 

[nalle59]

Thanks for your message ,I have structural calculations from the engineer he does not do calculations for building materials .I can do scale drawings but do not feel confident to calculate the timber correctly.

You just need to do a take off from the drawings - if you've got scaled drawings it's pretty easy. Send me the drawings if you like and I'll take a look tomorrow - don't throw away £90! It's first year Uni stuff, but if you don't feel confident I don't mind helping you out .

Thank you for your extremely kind offer I appreciate it.I have had three more carpenters come around to give quotes and all have agreed to work out the amount of wood needed .Hopefully reasonable quotes .
Thank you again.

 

[hotrod]

Good luck, a decent chippy should have no problem telling you what's required.