Should I use boards, such as anti-racking (‘racking’) boards, as part of a hempcrete wall?

You should not use boards that are not vapour-permeable (or not sufficiently vapour-permeable) such as OSB or ply except as temporary shuttering boards – used to shutter wet-cast hempcrete. There are specialist vapour-permeable racking boards, such as Econic. If possible, it is better to add boards after wet-cast hempcrete has fully dried, as even vapour-permeable boards will significantly slow down the drying process. 

Can I build a passive house with hempcrete? 

Yes. You may wish to combine the hempcrete with other types of natural insulation such as wood fibre board to reduce the wall thickness somewhat. However, the hempcrete element, making up the bulk of the wall thickness, will provide greater thermal mass than most other natural insulations, and will increase the thermal performance of the building. 

How much will it cost to build my hempcrete house? 

Our team can give a broad per-square-metre of usable floor space* figure for building a brand-new hempcrete house. However, the actual cost will depend on how the building is designed, including design of the structural frame, the other materials involved and types of finishes, as well as factors such as ease of access to the site. If you would like a specialist contractor to accurately price the construction of your building, you will need to have detailed construction drawings, showing full dimensions and all elements of the wall-, roof- and floor-build-ups. We [or our sister companies] can offer specialist services to get you to this point, whether you have hand-drawn sketches on paper, planning drawings for a building not yet designed for hempcrete, or simply a vision of what you want to achieve. 

*include ground floor, first floor and any floors above

What mixing ratio should I use for hempcrete?

Ratios for mixing hempcrete in a large forced action pan-mixer, or spray machine (bags of binder to bales of hemp shiv to water volume) are given in the individual product pages. If you are mixing on a smaller scale, for example in a cement mixer (Belle mixer), you can use “this rule of thumb” ratio to measure mix quantities out by volume (e.g. in buckets). This mix ratio works for all hempcrete binders, with small adjustments to the amount of hemp if your mix is slightly too dry, or slightly too wet.

Small batch hempcrete “by volume” mix:   3-3.5 hemp shiv : 1 binder : 1 water 

If you’re mixing in a Belle mixer, please watch this video.

Can I use hempcrete to insulate a solid masonry wall in an old building?

Yes. Hempcrete, either in wet-cast or precast block form, can be used to insulate existing stone or brick walls internally – internal solid wall insulation (ISWI) – or externally (ESWI). It needs to be used with other vapour-permeable materials – for example lime or clay plaster, lime render and lime mortar. Generally it should not be used internally where the walls are below external ground level. We usually recommend using between 100 mm (min.) and 200 mm (max.) hempcrete internally, depending on the amount of space you can afford to lose from the internal dimensions. Used externally the hempcrete can be thicker than 200 mm if this can be accommodated.   

Can I use hempcrete instead of concrete?

In comparison with concrete, hempcrete: 

  • is much less dense than concrete (at around 300 kg/m3 compared to over 2,000 kg/m3)  
  • is not a load-bearing material 
  • has a plant aggregate rather than stone 
  • has high vapour permeability, as opposed to very low vapour permeability 
  • is an insulation and mass material, rather than a mass material. 

Where should hempcrete NOT be used?

Hempcrete is a non-structural medium density walling and insulation n material with a plant aggregate. It is not suitable for use as a load-bearing material, and should not be installed at or below external ground level, or anywhere else where it may be exposed to standing or running water. In some specific circumstances, hempcrete can be used to line out and insulate below-ground rooms. Please read our information sheet to find out more, and make sure your hempcrete installation will not fail through poor detailing. 

How much will I need?

For hempcrete (wet-cast or blocks), or for lime plaster or render materials, we usually recommend allowing 5% for wastage/cutting on top of the volume you think you need. However this is obviously at the customer’s discretion. If you are calculating the area of plaster or render needed, don’t bother subtracting the area of any window or door opening under 2 square metres as the area of the reveals will usually make up the difference. For openings over 2 square metres in area, just subtract the balance over 2 m2 in each case.

Can I return a product?

Once dispatched, I’m afraid we cannot accept returns, so it is particularly important that you ensure that the quantities you’ve ordered are appropriate for your needs. 

Can I collect from you? 

Our warehouse is not set up to accept collections, but we are happy to arrange delivery to all parts of the UK by pallet (or ParcelForce or other carriers for certain products). 

How do you price your delivery?

We deliver to all of the UK.  The country is divided into zones for the purposes of pallet delivery pricing.

Do you offer free delivery if I spend a certain amount? 

We can currently only offer free delivery on full pallets of Tradical Thermo (53 bags for tail lift delivery, 60 bags if there is a forklift on-site). When you request a quote from us, we will do our best to offer to best price for delivery to your area.

Do you offer next day delivery? 

Yes. We also offer pre-10 am and pre-12 noon delivery options, deliveries timed to a two-hour slot, and Saturday AM deliveries.  Please select your desired delivery type in the Request a Quotation form.

How long do your deliveries take? 

Our standard (‘economy’) pallet delivery takes two to three working days.  So for example, if the material leaves our warehouse on a Monday, it will arrive with you on Wednesday or Thursday.  Please note with standard delivery, our pallet network does not advise a specific time slot and deliveries will arrive between 8.30 am and 5.00 pm.  The customer will therefore need to be at the delivery address during these times for both days until received.  We always take a contact telephone number with the order, so the pallet network can contact you if problems arise. 

Can I get technical advice on my project from Natural Building Store? 

The NBS team will be happy to provide technical information and advice on the products and materials we sell.  If you would like more in-depth technical help with the design or specification of your project (new-build or retrofit) members of the team can provide paid-for consultancy sessions.  These are usually provided in two-hour slots.  Typically this is by Zoom, but telephone or in-person options are available. 

Can I pay by bank transfer?

Currently we can only take payment by bank transfer. The payment details will appear on your invoice or proforma invoice.

Can you send me a pro forma invoice? 

This option is available. Please make this request in the Order notes box, when you Request a Quotation .

Do I need to sign up to place an order?

No, you do not need to register to place an order with us. You can insert your billing and shipping details when you Request a Quote. If you do register with us, you can view your pending quotations, orders and save your billing and shipping details, to save entering them manually.

Alternatively, you can place an order by calling us by phone at: 01629 34 34 20 or by email at:

Can I get a product sample?  

We don’t generally offer samples. However, the majority of our materials do not have a minimum order size, so you can order a single item as a test item if you wish.

Hempcrete blocks are sold in whole pallets only.  However architects or contractors should contact us if a sample section of block is needed.

What are your opening times? 

Our office is open from 9am to 5pm, Monday to Friday. Materials paid for on a weekday will generally leave our warehouse the next working day. 

What makes a building product sustainable?

We take a holistic approach to sustainability and believe in achieving high thermal performance through using materials with low embodied energy and proper end-of-life consideration. All of the products that we specify take consideration of:

  • Technical Performance
  • Embodied energy 
  • Health and Wellbeing
  • Local supply chains where possible
  • Resource efficiency
  • Potential for Recycling and Re-use
  • Ethical manufacture and Social Value

What is the Natural Building Store?

The Natural Building Store is an online store specialising in cutting-edge bio-based and highly sustainable building products. With an experienced team with specialist knowledge in specifying vapour-permeable construction build ups, we are dedicated to only stocking the best sustainable building materials.