Timber Grade: TR26
Timber Depth: 47mm
Timber Widths: 72, 97, 122, 147mm
Posi-Joists ordered here are intended for domestic floors only or flat roofs with a build up weight not exceeding 100kg per m2.
When you order Posi-Joists online with us, you'll also receive all necessary bracing timber, detailed drawings & virtual 3D model to work from, and calculations that you can submit to building control.
Treatment is not included—please let us know if you require this. Please note, this will incur a 10% increase in cost.
Step 1: Measure Your Building
Measure your building to assess what span you'll need your Posi-Joists to be and how many joists you'll need. You can either space your joists at 400 or 600 centres. If you're unsure, give us a ring and we'll talk you through it. It only takes a few minutes.
Step 2: Place Your Order
Select the depth of joist you require (deeper joists will span further), the span and the spacing, then add any drawings you might have. Don't worry if you don't have any—we will give you a ring if we need more information.
Step 3: We'll Phone You & Send a Design
Before even looking in the direction of a saw, we'll give you a ring to check all your measurements are correct. If everything looks good, we'll then send you our design for you to have a look through. If you need to make any amendments, we're always happy to do this.
Step 4: We'll Begin Manufacturing & Arrange Delivery
Once you've confirmed your order, we can begin manufacturing your Posi-Joists. One of our team will be in contact to arrange delivery on a day that suits you.
💪 Strength: The main benefit of the Posi Joist lies in its inherent strength and stiffness. Thanks to the clever combination of timber and steel in their design, Posi-Joists can span greater distances than solid timber, reducing or even eliminating the need for load-bearing walls or steel beams. Posi-Joists are also available in a range of depths—you can specify these yourself or we can work out which will be most cost-effective for your project.
🚽 Service Routing: Thanks to their open-web structure, Posi-Joists can accommodate various services without modification. With solid joists, an installer would have to drill, cut and hack away material, potentially limiting their strength and performance. Posi-Joists allow, in theory, an infinite amount of paraphernalia to be installed through the joists.
🏋️♂️ Weight: A Posi Joist uses less material to achieve the same strength as solid timber, making it significantly lighter. This is a major advantage if you're working on a site that can't accommodate a crane or if you want to avoid the associated costs.
🔨 Ease of installation: Posi-Joists are manufactured to the size of your building and can be simply dropped into place. If your building isn't perfectly straight (which, let's be honest, most old buildings aren't), Posi-Joists can be supplied with trimmable ends.
✏️ Quality: Posi-Joists are designed in specialist software and produced under factory-controlled conditions, ensuring an unmatched level of quality every time.
🏡 No shrinkage: Posi-Joists don't suffer from shrinkage or distortion, a typical cause for a squeaky floor.
Posi-Joist Span Calculator
Enter your joist type and desired span below to see a list of Posi-Joists that will clear span this distance.
How much do Posi-Joists weigh?
What's included?
All strongback bracing timber is included in the price. If you need restraint straps, please add these separately here.
Does the span include bearings?
Yes, if your joists are sitting on your bearings, please include these in your span measurement.
How does ordering work?
After you've placed your order, we'll give you a ring to confirm your measurements, delivery location, delivery dates/times and any other essential pieces of information before we begin manufacturing your products. This gives you some time to let us know if anything needs changing before it's too late. Once you're fully happy and have given us the go-ahead, we'll begin manufacturing your joists ready to be delivered for your specified date.
Can I supply more measurements?
Yes—either use the 'order special instructions' box in the basket or send us an email with any specific requirements you may have along with your name and/or order number.
What are your delivery options?
We can deliver trusses, joists or glulam in as little as 5-10 working days. The price for delivery depends on your location, which can range from £80 to £350. We will ring you after you've placed your order to confirm which day you'd like us to deliver on using our own fleet of vehicles.
For metalwork, it'll be delivered in 1-3 working days using a courier service and costs £20. If spending more than £250 on metalwork, delivery is free.
Is bracing timber included?
Yes—all strongback bracing timber is included in the price above.
Do I need a structural engineer?
No, you don't need a structural engineer. We will design the roof truss and provide you with the necessary structural calculations for building control.
Are Posi-Joists treated?
99% of the time Posi-Joists are not treated. Treatment is only necessary if you live in the red marked areas on this map. If you do require treatment, please get in touch.
"I purchased a Posi Joist flat roof system from Tailor Made Designs for a domestic single story extension. From the moment I first contacted them they were fantastic. Owain and Philip gave superb advice and the quote included detailed plans, structural calculations and a 3D model which made so easy to understand. I think using Posi joists saved well over a week and a half of time and labour costs. Thank you Philip and Owain for all your help and advice and if I ever need to build another roof again I will come to you and I will recommend you to everyone!"
— Peter Advenzia Smith