As a leading garden room provider, we are asked frequently about the different quality of SIPs that are on the market and what the important areas to look out for are.

Here we have compiled a list of what we believe are the most important things to check before building your garden room from SIPs.


  • At Hawksbeck, we only use accredited manufacturers. The SIP manufacturers we use are approved by the STA (Structural Timber association) and have UKAS approved accreditations.
  • We make sure our manufacturers use CATG for our Sipmark ISO9001 which certifies the design, manufacture, storage, distribution and sale of timber frame and SIP buildings (SIP wall, floor and roof panels). If you don’t have this you are not a certified manufacturer of SIPs panels.
  • It’s important to check what structural tests your manufacturer is doing. Our SIP manufacturers have structural testing done on all the panels regularly. They perform two types of testing; compression and racking tests.
  • We work with our manufacturers to make sure we use the correct panel to support the structure of our garden rooms. This is checked by a structural engineer and the building inspector.
  • Has your SIP building be checked and signed off by a structural engineer?
  • Here are some areas the engineer will check;
    • the maximum span the roof timbers can go to support the SIP roof.
    • the strength of the floor panels (if the correct thickness, centres and spins are being used), if for example, they need to support the extra weight of gym equipment for example.
    • if the correct extra thick timbers, called lintels, are needed to support the opening in the walls for windows and doors.
  • Does your SIP manufacturer’s timbers come with CE mark and have a PEFC registration? PEFC monitor all timber used by manufacturers for sustainability, quality and this is essential. We only use high grade C24 PEFC tracked timber.
Inside garden office, Essex
Contemporary garden room design


Thermal transmittance (reciprocal of R-value), also known as U-value, is the rate of transfer of heat through a structure. The lower the u-value the better insulated a building is. U-value rates are set out by building regulations.

The u-values provided by our manufacturers enables us to determine the correct panel to use, not only to ensure that you are warm in the winter and cool in the summer, but also which panel will provide the correct u-value to pass building regulation approval from the building inspector.

Please see the table at the bottom of the link for Hawksbeck Garden Room u-values; for further information.


Is the SIP manufacturer being audited? Are they doing batch testing on their products for integrity?

Our manufacturers are required to test every SIP panel batch they produce for inspection when audited.

All of this may seem a little overwhelming, so please give us a call today on 01277 414586 and we can guide you through the process of building the perfect garden room, with the reassurance that we are using the best SIPs on the market.