Ask a tradesman


What size wooden rafters and wall plate do i need to carry double glazed glass. glass size 3000 x 650. 40kilos. lean-to conservatory 5m x 3m

2 Answers from MyBuilder Conservatory Installers

Best Answer

Hi Biggles_93
Is this a do it yourself job ??

Have you ordered the glass ? Is it the self cleaning, heat resistent toughened sealed unit type ?
Check that it can be made that length or does it come in two with a buntin bar to join them.
When calculating weights of this type you should always take into consideration extras like how much extra weight would be on the roof if it had 3 to 4 inches of snow on it or a seventy mile an hour wind force against it.
Bearing this in mind :
The wall plate does not need to be deep so long as you have secured it and sealed it thoroughly to the back wall.
To help with the weight load you can incorporate a purlin half way up the 3M depth and from left to right and then supported on the end frame wedges. Would this be an option ? Rafters 125mm to 150mm.
I presume you must have some type of external bar and cap that sits on the wooden rafter that accepts the glass ? how deep is this.

Hope this helps

Regards John


Answered 23rd Nov 2011

Hi Biggles_93,

I presume that you are using 24mm or 28mm Double Glazed Toughened Glass Units. 150mm x 75mm Timbers with have sufficient structural integrity to support these units. you dont need a Muntin Bar or Split units as the units are only 650m wide and have very little deflection within the unit. Do not picture frame the whole unit (only top and sides) this will ensure good water run off and will eliminate static water. A thixotropic mastic should be used to bed the units in. A 10 degree minimum pitch for roof if possible. If the roof pitch is less then upgrade to 200mm x 75mm rafters. Glass gable ends are a great way to finish the roof off. If the roof is going onto Wallframes, it would be advisable to construct a 75mm x 75mm ring beam around the top of the frames

Hope this info helps you

Kindest Regards

Vince and Greg


Answered 26th Nov 2011

Post your job to find high quality tradesmen and get free quotes

Can’t find an answer? Ask a new question

Question Categories