Steel Framed Building Exterior Finishing Guide

A guide on completing the exterior finish of your Steel Framed Garden Room, once the metal structure is completed.

Before you begin your exterior cladding, you should consider a few things.

Firstly, if you are wanting electrics included, such as up-down wall lights, & spotlights in any soffit overhang - you should get the works & wiring ready to feed through your wall make up. You will need to secure your exterior wall make-up around your cables as required (take care not to screw into your cable when securing your battens.

Secondly, we advise completing this stage before you complete your flat roof make up (with the potential exclusion of the final exterior finish - see later) . This way, you create the correct depth/finish for which your roof boarding, will terminate at.

Step 1: First, to improve thermal efficiency, & stop cold bridging, you need to board the exterior of the streel framed structure with 25mm rigid insulation (Celotex or Kingspan).

This insulation can be temporarily held in place with glue, or a few fixings into the frame. It will be held much more securely when you secure the battens later.

When boarding around you door opening (any other windows or other items if a bespoke modular room), keep your finish flush with the edge & not proud.

Note: Ensure the bottom of your insulation doesn't touch your concrete base or other floor, which could result in moisture bridging.

Step 2: Next, using a staple gun, secure your breathable membrane to your OSB. This is just to hold the membrane, it will be secured more thoroughly by your battens in the following steps.

Overlap your membrane by the indicated margins (approx. 150mm). Your membrane should also sit slightly lower than the bottom line of insulation, as well as wrap around the reveal or your door opening(s).

Step 3: You now need to secure your exterior battens, which must be treated & secured with galvanised fastenings, at appropriate spacings.

You battens should be spaced at approx. 400mm centres, as well as around any apertures (doors), & on both sides of your corners.

Note: If your exterior finish will run horizontally (standard method), your battens should be fitted vertically. If you chosen exterior finish will run vertically, you battens should be fitted horizontally.

Additional Note: On 

Step 4: You should now install your chosen door, or windows if applicable, before you install your exterior finish. 

Additionally, if having any exterior lights, make sure the feeds (non-live) are sticking out in the correct positions, ready to feed through your exterior finish.

Note: You may need to complete any door/window beading or siliconing once your exterior finish has been completed.

Step 5: You can now install your chosen exterior finish, as per their instruction guidelines. 

Typically, this will be a form of cladding, such as shiplap timber, or even better a Upvc/Composite embossed cladding - ideal for their lightweight & water-resistant makeup.

Note: You should consider installing the exterior finish once you have installed your Warm Flat Roof makeup, exluding fitting the Elevate EPDM rubber cover. Providing you have not planned a bespoke soffit overhang, or a separate fascia board - your exterior finish can then go all the way to the top of the roofing board, ready to have your roofing edge trims fixed to,