> For the complete documentation index, see [llms.txt](https://docs.bimcat.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.bimcat.org/user-manual/usage/tallycat-beta/export-to-ec3-synchronize-with-ec3/ec3-builder-support.md).

# Web Builder Support

After exporting a Revit project, Web App will attempt to detect which building elements could be refined by the **Web Builders**. These builders are a set of helper tools which allow you to automatically recognize and refine typical assemblies. For example, a single **Concrete** layer could be turned into **Reinforced Concrete**, a **Metal Stud** layer mass could be calculated according to its volume and other properties, etc.

To use this feature, after opening an exported web project in a browser or using the [Open in Web App](/user-manual/usage/tallycat-beta/open-in-ec3.md) window, click the **Next Decision** button in the [Revit](/user-manual/usage/tallycat-beta/export-to-ec3-synchronize-with-ec3/ec3-export-results-overview/revit-view.md) or [Custom](/user-manual/usage/tallycat-beta/export-to-ec3-synchronize-with-ec3/ec3-export-results-overview/custom-view.md) view.

<figure><img src="/files/47SMfZpXtRgcpWFTiBMl" alt=""><figcaption></figcaption></figure>

It will highlight the next element is proposing to apply a builder to.

<figure><img src="/files/gUZTbpxb9dGaGGqjGpjj" alt=""><figcaption></figcaption></figure>

For example, in this case it's a **Concrete** layer which could transformed into **Reinforced Concrete** by automatically adding a rebar. To do this, click the layer's quantity.

<figure><img src="/files/7TrgkabZaDadJVC8kquB" alt=""><figcaption></figcaption></figure>

You will see two options: **Concrete By Area** and **Concrete By Volume**, so you can choose which dimensionality to use for this layer.

After clicking either of them (for example, **Concrete By Volume**) the builder dialog will open allowing you to choose how to calculate the required amount of rebar for this element.

<figure><img src="/files/SijGy88yUgpWDDk24AMO" alt=""><figcaption></figcaption></figure>

By clicking **Add Rebar By Concrete Volume, Add Rebar By Reinforcing Ration** or **Add rebar By Length**, you'll make the builder to automatically add a Rebar layer for the Concrete layer using the selected principle to calculate the quantity.

<figure><img src="/files/KNzFvLXx4b1HfTtIwVtm" alt=""><figcaption></figcaption></figure>

By clicking the **Accept** button you'll confirm the calculated quantities and get the reinforced concrete assembly.

<figure><img src="/files/pfYPUNKcrYFCDc35ynG6" alt=""><figcaption></figcaption></figure>

The EC3 Builders could help with **Metal Stud** layers too.

After the export, Web App often is unable to reliably calculate the quantity of such layer, because it lacks material density. In this case, instead of quantity, the **#VALUE!** error is displayed in the quantity filed.

<figure><img src="/files/BV91wN8e0asYAiVHkQAr" alt=""><figcaption></figcaption></figure>

After clicking the quantity field of such layer, you can apply the **Metal Stud** builder to it.

<figure><img src="/files/Ful70GWq4Hx3p7HM8qgo" alt=""><figcaption></figcaption></figure>

It will help to calculate the realistic quantity.

<figure><img src="/files/190yEz2Uj7RieLhIMu7D" alt=""><figcaption></figcaption></figure>

After clicking the **Accept** button, you will get the properly calculated **Metal Stud** layer.

<figure><img src="/files/TxHadcBrHq6InrFvpm4I" alt=""><figcaption></figcaption></figure>

Apart from proposing to apply a builder, the **Next Decision** button also highlights other problems in the project, like missing quantities or EPDs, lacking an accurate material category, etc.