Posi-Joists are available in 5 standard depths, ranging from 202mm to 421mm, and can be made to virtually any span, from as little as a metre to over 12 metres. The width will also range from 72mm to 147mm depending on the span, depth and its intended use as either a floor, flat roof or rafter. Select your desired depth, span and spacing above to see what's possible.
Posi-Joists ordered online are intended for domestic floors only or flat roofs with a build up weight not exceeding 100kg per m2. Contact us for other Posi-Joist requirements.
Every project is unique, which is why we offer a comprehensive design service for all Posi-Joist orders. By uploading your architectural plans above, or even just a quick sketch if you don't have any of these, our design team can provide a full structural floor layout and 3D model. We ensure that every joist is manufactured to the exact millimetre, arriving on-site ready for immediate installation. This "kit" approach eliminates on-site waste and ensures your project stays on schedule and within budget.
We deliver Posi-Joists to most of England and Wales in as little as 5 days using our fast-track delivery service. Thanks to our in-house team of drivers and vehicles, we're able to deliver across the country with greater flexibility than would be possible with outsourced couriers. Our team of designers and manufacturing staff can rapidly turn your order around, getting you back on track if factors outside your control have delayed things on site.
"Philip was so helpful, this was my first time ordering trusses and he was so very helpful. They are on in a day and today felt and battened. I will order from you again. Normally the guys cut the roofs onsite. We are behind and I needed to gain days back. Fabulous!!!"
💪 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.
🚽 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.
🏋️♂️ Weight: A Posi Joist uses less material to achieve the same strength as solid timber, making it significantly lighter.
🔨 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, 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.
Not sure which depth you need?
Enter your joist type and desired span below to see a list of Posi-Joists that will clear span this distance.
How to Order Posi-Joists Online
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.
Joist Specifications
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.
What's included with your order?
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.
How much do Posi-Joists weigh?
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